Arthropod Pests, Nematodes, and Microbial Pathogens of Okra (Abelmoschus esculentus) and Their Management—A Review

Abstract

Okra (Abelmoschus esculentus) is an important agricultural crop of the Malvaceae family, cultivated across tropical, subtropical, and warm temperate regions. However, okra production faces numerous challenges from diverse pest species, including insects, nematodes, arachnids, and mites, that significantly reduce its yield. Major economic pests include the cotton aphid, cotton spotted bollworm, Egyptian bollworm, cotton mealybug, whitefly, cotton leafhopper, cotton bollworm, two-spotted spider mite, root-knot nematode, reniform nematode, cotton leaf roller, and flea beetle. Additionally, less prevalent pests such as the blister beetle, okra stem fly, red cotton bug, cotton seed bug, cotton looper, onion thrips, green plant bug, and lesion nematode are also described. This review also addresses fungal and oomycete diseases that present high risks to okra production, including damping-off, powdery mildew, Cercospora leaf spot, gray mold, Alternaria leaf spot and pod rot, Phyllosticta leaf spot, Fusarium wilt, Verticillium wilt, collar rot, stem canker, anthracnose, and fruit rot. In addition to these fungal diseases, okra is also severely affected by several viral diseases, with the most important being okra yellow vein mosaic disease, okra enation leaf curl disease, and okra mosaic disease, which can cause significant yield losses. Moreover, okra may also suffer from bacterial diseases, with bacterial leaf spot and blight, caused primarily by Pseudomonas syringae, being the most significant. This manuscript synthesizes the current knowledge on these pests. It outlines various management techniques and strategies to expand the knowledge base of farmers and researchers, highlighting the key role of integrated pest management (IPM).

1. Introduction

Okra (Abelmoschus esculentus (L.) Moench), commonly known as lady finger or gombo, is one of the most widely cultivated and consumed crops of the Malvaceae family [1]. The Malvaceae family also includes several other important plants of economic significance such as cacao, cotton, durian, and ornamental hibiscus [2]. In its early classification, okra was included in the Hibiscus genus and was often referred to as Hibiscus esculentus in older publications.

Its cultivation is adaptable to a wide range of geographical locations, as it can be grown in regions with varied climatic conditions such as tropical, subtropical, and warm temperate regions [3], leading to its widespread cultivation and commercial use in numerous countries [4]. Global okra production shows significant growth, increasing from 1.8 million tons in 1972 to 11.2 million tons in 2022, with India accounting for 61.2% of the global total production [5]. India’s leading role as the largest producer of okra globally has also made it a focal point for extensive research on okra cultivation, pest dynamics, and management strategies. Consequently, a substantial portion of the studies referenced in this manuscript originates from India, reflecting the country’s significant contribution to advancing okra research and management practices. Other countries, such as Nigeria, Mali, Pakistan, Sudan, Côte d’Ivoire, and Iraq also play notable roles in contributing to the global production of okra [5].

Although the crop has multiple uses, its primary cultivation and consumption are focused on the green, soft fruits of the plant, which are rich in minerals such as iron and irodine and vitamins A, B, and C and also possess a significant amount of protein and oil, approximately 20.0% of each [6,7,8]. This vegetable is an essential source of viscous fiber and is reported to contain low levels of sodium, saturated fat, and cholesterol [8,9]. Okra seeds and leaves have been reported to have antidiabetic, antioxidant, and antimicrobial properties. Studies have proved that okra has various human health benefits, such as blood sugar regulation, inflammation reduction, and even cancer prevention, and it has been traditionally used in herbal medicine [10,11]. Okra has also found medical application as a plasma replacement or blood volume expander [12,13,14,15]. It was found that an alcohol extract of the leaves can improve renal function, reduce proteinuria, and alleviate renal tubular–interstitial diseases by eliminating oxygen free radicals [16,17]. The oil- and protein-rich fruits have been utilized for oil production on a limited scale [18]. Moreover, the crude fiber in mature okra fruit and stems is used to make paper [19].

Okra is vulnerable to several significant challenges posed by fungal, viral, and bacterial pathogens and arthropod and nematode pests, which can significantly affect its cultivation success [20,21]. About 72 insect pest species have been recorded on okra crops [22,23], of which 48 species have been reported as most destructive [24]. Pests can cause either major or minor damage; the most common arthropods and nematodes include pests such as the cotton aphid (Aphis gossypii Glover 1877 (Hemiptera: Aphididae)), cotton spotted bollworm (Earias vittella Fabricius 1794 (Lepiodeptera: Nolidae)), cotton mealybug (Phenacoccus solenopsis Tinsley 1898 (Hemiptera: Pseudococcidae)), whitefly (Bemisia tabaci Gennadius 1889 (Hemiptera: Alyerodidae)), cotton leafhopper (Amrasca biguttula Ishida 1912 (Hemiptera: Cicadellidae)), cotton bollworm (Helicoverpa armigera Hübner 1805 (Lepidoptera: Noctuidae)), two-spotted spider mite (Tetranychus urticae Koch 1836 (Acarida: Tetranychidae)), and root-knot nematodes (Meloidogyne spp.). Furthermore, less common pests, including the blister beetle (Mylabris pustulata Olivier 1795 (Coleoptera: Meloidae); M. phalerata Pallas 1781 (Coleopttera: Meloidae)), okra stem fly (Melanagromyza hibisci Spencer 1961 (Diptera: Agromyzidae)), cotton looper (Anomis flava Fabricius 1775 (Lepidoptera: Erebidae)), green plant bug (Nezara viridula Linnaeus 1758 (Hemiptera: Pentatomidae)), and lesion nematode (Pratylenchus brachyurus Godfrey 1929 (Rhabditida: Pratylenchidae)), have also been noted to pose risks to okra cultivation. In this manuscript, arthropod and nematode pests are categorized into “major” and “minor” groups based on the extent of the economic damage they cause to okra production, resulting in lower yields and compromised market value.

Similarly, okra production is affected by many fungal and oomycete diseases that adversely impact both the quantity and quality of the crop [25]. Major diseases include damping-off, powdery mildew, Cercospora leaf spot, gray mold, Alternaria leaf spot and pod rot, Phyllosticta leaf spot, Fusarium wilt, Verticillium wilt, collar rot, stem canker, and anthracnose. Virus infections are a significant factor contributing to the generally low productivity of okra in many countries. Field infection incidence can reach as much as 88.0% [26], leading to nearly complete yield losses [27,28]. The three most critical viral diseases impacting okra are okra yellow vein mosaic disease, okra enation leaf curl disease, and okra mosaic disease [29]. In addition to viral threats, okra is also affected by bacterial pathogens, most importantly Pseudomonas syringae, causal agent of the bacterial leaf spot and blight of okra, which can result in reduced crop productivity and quality [30].

Okra pathogens and pests exhibit a range of symptoms on crops, affecting yield and quality. Detailed images of the pests, the damage they cause, and symptoms of the diseases are available in the European and Mediterranean Plant Protection Organization (EPPO) Global Database [31], which serves as a valuable resource for researchers and practitioners.

To address the challenges posed by these pests and pathogens and given the significance of okra as a crop, extensive research has been conducted under greenhouse and field conditions to study pest dynamics and develop effective management practices (Figure 1 and Figure 2). Farmers often rely on chemical plant protection products, which can be relatively inexpensive. However, using these products can lead to problems such as pest resistance, pesticide residues, adverse effects on beneficial fauna, and other environmental concerns [32,33]. Consequently, alternative pest management measures are crucial, including biological approaches by applying biologically active plant products and natural enemies; cultural practices such as intercropping; physical tools by employing traps and water management; or genetic resistance through plant breeding, which is a promising, effective, economical and bio-rational approach to pest management [34]. Alternatively, control may involve biopesticides, which are cost-effective, biodegradable, and non-toxic to humans [35,36]. Integrating these solutions under the integrated pest management (IPM) framework can be a cost-effective and sustainable approach to pest management.

Therefore, this review aims to provide information for researchers, farmers, extension workers, and other stakeholders involved in okra production. It can help increase their awareness of the most important pests and diseases affecting okra and their potential impact on production. It can also provide guidance on the most effective management strategies, which can help improve the yield and quality of okra crops.

2. Okra Animal Pests and Their Distribution

Table 1. Distribution of major and minor arthropod and nematode pests affecting okra.

	Taxonomical Group	Common Name	Scientific Name	Global Distribution	Countries Reporting Pest as Widespread
Major pests	Hemiptera	Cotton aphid	Aphis gossypii Glover 1877	Present in most countries across North and South America, Europe, Africa, Asia, and Australia [39]	Singapore [39]
	Hemiptera	Cotton mealybug	Phenacoccus solenopsis Tinsley 1898	Present in all countries of North and South America, as well as in many countries across Africa, Asia, and Australia [40]	China, India (due to the difficulty of identifying the species, the pest has been reported to be likely more widespread than the countries listed) [40]
	Hemiptera	Whitefly	Bemisia tabaci Gennadius 1889	Present in all countries of North and South America, as well as in most countries across Africa, Europe, Asia, and Australia [41]	Cape Verde, Egypt, Sudan, Zimbabwe, Belize, Bermuda, Haiti, Martinique (France), Mexico, Paraguay, Trinidad and Tobago, Venezuela, China, India, Taiwan, Yemen, Azerbaijan, Cyprus, Greece, Italy, Malta, Spain, Turkey, Australia [41]
	Hemiptera	Cotton leafhopper	Amrasca biguttula Ishida 1912	Present in East Asia and Southeast Asia, with some regions of Africa [42]	India, Pakistan, Bangladesh [42]
	Lepidoptera	Cotton spotted bollworm	Earias vittella Fabricius 1794	Present in East Asia, Southeast Asia, parts of the Middle East, and Australia, with some presence in Southern Europe, specifically in Spain [43]	India, Bangladesh, North Korea [43]
	Lepidoptera	Egyptian bollworm	Earias insulana Boisduval 1833	Present in Eastern Europe, East Asia, Southeast Asia, parts of the Middle East, Australia, and Africa [44]	India, Spain [44]
	Lepidoptera	Cotton bollworm	Helicoverpa armigera Hübner 1805	Present across most countries of South America, Africa, Europe, Asia, and Australia. It is notably absent from North America, northern countries of South America, and Mongolia [45]	Algeria, Egypt, Kenya, Libya, South Africa, Zimbabwe, Bangladesh, China, India, Iran, Japan, Laos, Saudi Arabia, Syria, Taiwan, Tajikistan, Yemen, Albania, Bulgaria, Cyprus, Greece, Portugal, Romania, Spain, Ukraine, Australia, New Caledonia (France), New Zealand [45]
	Lepidoptera	Cotton leaf roller	Syllepte derogata Fabricius 1775	Present in many African countries, East Asia, Southeast Asia, and Australia. It is notably absent from Europe and the Americas [46]	Nigeria [46]
	Coleoptera	Flea beetles	Nisotra uniformis Jacoby 1906 & N. sjoestedti Jacoby 1903	Reported presence in Sub-Saharan Africa [47], with N. uniformis and N. stotjedii recorded in Nigeria [48,49,50,51] and N. uniformis also documented in Ghana [52], Sudan [53,54], and Burkina Faso [55]	N/A
	Rhabditida	Root-knot nematodes	Meloidogyne spp.	M. incognita is present in all countries of the Americas, Oceania, and most countries of Europe, Asia, and Africa, excluding Norway, Sweden, Finland, Ireland, Chad, South Sudan, Eq. Guinea, Rwanda, Burundi, Namibia, Cambodia, North Korea, and Laos [56]	In the case of M. incognita: Chile, Argentina, Brazil, Bolivia, Guyana, Venezuela, Ecuador, Guadeloupe, Dominican Republic, Cuba, Honduras, Mexico, USA, Australia, Fiji, Vanuatu, Samoa, Papua New Guinea, Vietnam, China, Bangladesh, Sri Lanka, Nepal, Uzbekistan, Turkmenistan, Yemen, Saudi Arabia, Egypt, Libya, France, Spain, Morocco, Senegal, Niger, Nigeria, Ghana, Liberia, Congo, Uganda, Tanzania, Malawi, Zambia, Angola, Madagascar, South Africa [56]
	Rhabditida	Reniform nematodes	Rotylenchulus reniformis Linford & Oliveira 1940	Present in parts of North America, Central America, South America, Sub-Saharan Africa, East Asia, Southeast Asia, and Australia. In Europe, its presence has only been recorded in Austria [57]	Mexico, Cuba, Belize, Brazil, Suriname, Venezuela, Colombia, Peru, Panama, Honduras, Dominican Republic, Gambia, Liberia, Côte d’Ivoire, Ghana, Togo, Nigeria, Cameroon, Angola, South Africa, Mozambique, Zimbabwe, Tanzania, Kenya, Somalia, Sudan, Egypt, Oman, Iraq, Pakistan, India, China, Japan, Thailand, Philippines, Indonesia, Australia, Solomon Islands, Fiji [57]
	Acari	Two spotted spider mite	Tetranychus urticae Koch 1836	Recorded in most countries in Europe, Asia, Africa, Australasia, Pacific and Caribbean islands, and North, Central, and South America [58]	N/A
Minor pests	Hemiptera	Red cotton bug	Dysdercus koenigii Fabricius 1775	India [59] and Pakistan [60,61]	N/A
	Hemiptera	Cotton seed bug	Oxycarenus hyalinipennis A. Costa 1843	Has a worldwide distribution, including a first report in the Bahamas [62], as well as reports in Pakistan [63,64], India [65], Spain [66], Egypt [67], and the UK [68]	N/A
	Hemiptera	Green plant bug	Nezara viridula Linnaeus 1758	Widely distributed, especially in the southern USA, Central and South America, the Mediterranean, the Middle East, Africa, Malaysia, the Philippines, Indonesia, Japan, and the Pacific Islands [69]	USA, Mexico, Brazil, Uruguay, Argentina, South Africa, Sudan, Italy, Sardinia (Italy) Turkey, Afghanistan, India, Myanmar, Bangladesh, Vietnam, Indonesia, Japan, Australia [69]
	Diptera	Okra stem fly	Melanagromyza hibisci Spencer 1961 (Diptera)	Present in India [70,71]	N/A
	Coleoptera	Blister beetles	Mylabris pustulata Olivier 1795 & M. phalerata Pallas 1781 (Coleoptera)	Widely distributed in India, with many records on okra [51,72,73]	N/A
	Lepidoptera	Cotton looper	Anomis flava Fabricius 1775	Present in many countries of Africa, Oceania, South and Southeast Asia. It is notably absent in Europe and the Americas [74]	India, Northern Mariana Islands [74]
	Thysanoptera	Onion thrips	Thrips tabaci Lindeman 1889	Distributed across North America and present in most countries of South America, Oceania, Asia, and many countries in Africa. Present throughout Europe, except for Belarus [75]	China, India, USA [75]
	Rhabditida	Lesion nematode	Pratylenchus brachyurus Godfrey 1929	Distributed across Oceania and North America and is present in most countries of South America, Asia, and many countries in Africa. It is found throughout Europe except for Bulgaria and Italy [76]	Australia, Vietnam, Peru, Cuba, Puerto Rico (USA), USA [76]

presents an overview of the major and minor arthropod and nematode pests affecting okra, identifying the countries where these pests cause the most significant damage globally. The data have been compiled from the EPPO (European and Mediterranean Plant Protection Organization) Global Database [31], CABI (Centre for Agriculture and Bioscience International) databases, CABI Compendium [37], and PlantwisePlus Knowledge Bank [38]. It should be noted that for certain pests marked as ‘N/A.’ in the table, specific data on their level of prevalence are currently unavailable.

Figure 3 visually represents the prevalence of various okra animal pests, showcasing the number of countries where each pest is considered widespread. These data have been gathered from official databases managed by recognized authorities: EPPO, which oversees the EPPO Global Database, and CABI, responsible for the Invasive Species Compendium and the Plantwise Knowledge Bank databases. However, these data reflect only the recorded countries and may not capture the full extent of the geographical distribution [31,37,38]. This figure highlights which pests pose the greatest threat on a global scale, down to those that are less common. The data presented are specific to pests for which published prevalence information is available.

Figure 4 offers a global perspective on the distribution of okra arthropod and nematode pests, highlighting regions where these pests are most widespread. This spatial depiction underscores the widespread impact of okra pests across different regions.

3. Major Okra Pests and Their Management Strategies

3.1. Cotton Aphid (Aphis gossypii Glover (Hemiptera: Aphididae))

The cotton aphid (Aphis gossypii Glover (Hemiptera: Aphididae)) is known as a significant insect pest causing substantial damage to okra cultivation. The insect targets a wide range of host plants, as noted by its polyphagous nature [77,78]. An intense infestation of cotton aphids leads to the curling of leaves, stunted growth, and gradual drying and death of young plants [79]. The development of black sooty mold on the leaves is also observed as a consequence of feeding [80]. Additionally, dry conditions facilitate a rise in the population of cotton aphids, thereby rendering young plants more susceptible to infestations [81].

3.1.1. Cultural Control

Low dosages of nitrogen fertilizer applications have been shown to reduce cotton aphid populations and damage to cotton crops [82].

3.1.2. Biological Control

Biological management approaches for cotton aphids utilize natural predators such as lady beetles, lacewings, and parasitic wasps (Aphidius matricariae, Aphelinus semiflavus) to decrease A. gossypii populations [83,84].

3.1.3. Botanical Control

Moreover, herbal extracts derived from neem, turmeric, tobacco, and garlic have been identified as potential substitutes for synthetic pesticides against A. gossypii [85,86]. Papaya, khaki weed, lantana, and bell pepper extracts are also used to control cotton aphids [87]. Papaya contains highly poisonous chemicals, like saponins and alkaloids, which can be toxic to plant-sucking insect pests such as cotton aphids, spotted bollworms, and whiteflies [88,89]. However, the toxic level of these chemical compounds has not been evaluated against these pests or non-target organisms [90].

3.2. Cotton Spotted Bollworm (Earias vittella Fabricius (Lepiodeptera: Nolidae)) and Egyptian bollworm (E. insulana Boisduval)

The cotton spotted bollworm (Earias vittella Fabricius (Lepiodeptera: Nolidae)) and the Egyptian bollworm (E. insulana Boisduval), collectively referred to as shoot and fruit borers (OSFBs), are among the most damaging arthropod pests to the okra plant, leading to significant reductions in okra yield [91]. OSFBs can significantly damage okra at both the vegetative and fruiting stages. The adult female of these insects lays eggs on leaves, floral buds, and tender fruits, each laid separately. Upon hatching from eggs, small brown caterpillars bore into the top shoot and feed inside it before fruit formation, which can cause the shoots to wilt and dry out, developing side branches [92]. The caterpillars prefer attacking and boring into the fruits, if available, and feeding inside them, producing smaller and deformed fruits [92]. The larvae of OSFBs bore into the terminal growing shoots, floral buds, flowers, and fruits of the okra plant. This can result in the cessation, withering, and drying of the infested shoots and young leaves and the heavy shedding of floral buds and flowers [93]. The infested fruits become malformed and unsuitable for human consumption and the procurement of seeds. This can lead to a loss of up to 54.0% in marketable yield, plant vitality, and consumer appeal [94,95].

3.2.1. Chemical Control

Resistance to systemic insecticides in cotton spotted bollworms and Egyptian bollworms pose control challenges, yet using insecticides with different modes of action can curb resistance [15]. Biologically based insecticides such as emamectin and spinosad demonstrated potential as effective control products against bollworms [94,96], as do Rynaxypyr^® (FMC Corporation, Philadelphia, PA, USA) (chlorantraniliprole), cypermethrin, and flubendiamide, alone or with neem oil [97,98,99].

3.2.2. Botanical Control

Plant oils derived from neem, mahogany, pithraj, and karanj effectively control E. vittella, integrating well with IPM [97].

3.2.3. Biological Control

Trichogramma species have been identified as highly effective biological control agents for managing Earias sp., serving as parasitoids of eggs [100,101].

3.2.4. Microbial Control

Cry proteins from Bt, including Cry IA variants, have demonstrated substantial toxicity against E. vittella, leading to effective pest control [102]. However, resistance development in this pest is challenging, with field strains showing up to a 128-fold increase in resistance to Bacillus thuringiensis subsp. kurstaki (Dipel^® (Valent BioSciences, Libertyville, IL, USA)) following continuous exposure for several generations [103,104]. Additionally, Ahmad et al. [105] found varying resistance levels across different field populations to multiple Cry toxins, emphasizing the need for integrated management approaches to delay resistance development. This resistance, although significant, remains unstable, suggesting that rotational use of Dipel^® and other Bt products and formulations, along with regular monitoring, could help mitigate its impact [103,106,107].

3.2.5. Host Plant Resistance

Host plant resistance and varietal control are also cost-effective and safe approaches that can be used against the shoot and fruit borer as part of IPM programs. The okra genotype ‘SabzPari’ is effective in controlling fruit borer attacks [108].

3.2.6. Cultural Control

Using border crops promotes natural pest control, reduces insecticide use, and supports biodiversity, aligning with IPM strategies [109].

3.3. Cotton Mealybug (Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae))

The cotton mealybug (Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a significant polyphagous pest of okra with a worldwide distribution, originating from Central America [110]. This pest has been observed in notable proportions on various agricultural and horticultural crops, with the highest levels of infestations observed in members of the Asteraceae (21.4%), Solanaceae (16.0%), and Malvaceae (12.5%) families [111,112,113]. These widespread infestations have been associated with significant yield reductions, including losses of up to 60.0% in cotton, and potentially substantially impacting other crops such as okra [114].

Both nymphs and adults of the pest cause damage by sucking plant sap from the growing points, which results in stunted growth, yellowing of leaves, drying up, and in severe cases, plant death [115,116]. The extensive honeydew excreted by the mealybugs promotes the development of black sooty mold on leaves, inhibiting regular photosynthetic activity, promoting fungal growth, and further contributing to plant damage [115,117,118]. The pest’s polyphagous behavior and ability to oviposit on diverse host plants increases its potential for dispersal and adaptability, posing a substantial risk to agricultural and horticultural systems [119]. A study on the seasonal incidence of P. solenopsis on okra in India indicates that the population starts increasing in May and peaks in August [120]. The population shows a negative correlation with maximum temperature and a positive correlation with relative humidity. The damage caused includes a significant decline in plant vitality and yield loss [120].

3.3.1. Chemical Control

In the study of Ansari and Haseeb [121], the effectiveness of various insecticides and biopesticides was evaluated against P. solenopsis. Cypermethrin and Aza-d^® (Gowan Company, Yuma, AZ, USA) (azadirachtin) achieved the highest mortality levels of 90.0% and 96.7%, respectively, at 1% concentration. In another study, Actellic^® 50% EC (Syngenta, Basel, Switzerland) (pirimiphos-methyl) was effective in managing the pest on both Jew’s mallow and okra [122].

3.3.2. Botanical Control

Bala et al. [123] assessed the biocidal and repellent effects of methanol and ethanol leaf extracts from Andrographis paniculata and Eucalyptus globulus against P. solenopsis. At a 10% concentration, methanol extracts of A. paniculata achieved 100% mortality, while E. globulus achieved 96.1%.

3.3.3. Microbial Control

Khanzada et al. [124] evaluated several entomopathogenic fungi—Beauveria bassiana, Metarhizium anisopliae, Cordyceps farinosa, Purpureocilliam lilacinum, and Lecanicillium lecanii—for controlling P. solenopsis on okra. Higher doses of M. anisopliae and B. bassiana were effective, reducing mealybug populations by 83.7% and 80.0%, respectively. L. lecanii and P. lilacinus also showed notable effectiveness [124]. Additionally, L. lecanii alone and in combination with neem oil showed high mortality levels on various vegetables, with the highest effectiveness observed on okra [125].

3.3.4. Biological Control

Parasitoids and predators of P. solenopsis identified in the research of Suroshe et al. [126] include the encyrtid Aenasius bambawalei, which was predominant, and Promuscidea unfasciativentris, a key hyperparasitoid. Newly recorded parasitoids Aphanogmus sp. and Anastatus sp. were noted. In the study of Ibrahim [127], the efficacy of ladybird beetle (Chrysoperla carnea) larvae under semi-field conditions showed reductions of 90.5% to 96.0% for adult and nymph stages of P. solenopsis, suggesting that releasing 5 larvae per 100 nymphs can be effective for biological control. Mohamed [128] reported that the parasitoid Aenasius arizonensis exhibited a 12.3% parasitism rate against P. solenopsis, and the predator Nephus includens had a 4.6% predation rate.

3.4. Whitefly (Bemisia tabaci Gennadius (Hemiptera: Alyerodidae))

Whiteflies (Bemisia tabaci Gennadius (Hemiptera: Alyerodidae)) are sucking insect pests that pose a significant economic threat to okra. During early plant development, both nymphs and adults feed on leaf sap, typically on the underside, and secrete honeydew, which encourages the growth of sooty mold on the leaves, reducing the plant’s ability to photosynthesize [129,130]. In severe infestations, leaves become wrinkled and show browning symptoms, while the whitefly stunts growth and reduces the quality and yield of fruit by up to 80.0% [131,132].

In addition to causing direct damage, whiteflies also transmit okra yellow vein mosaic virus (OYVMV) and okra leaf curl virus (OkLCV) [133], resulting in significant yield losses, mainly when it occurs in the early stages of crop growth. Damaged plants show a 24.9% reduction in plant height, a 15.5% decrease in root length, and a 32.1% decrease in the number of fruits per plant, while stem girth is reduced by 16.3% [134].

3.4.1. Chemical Control

Plant defense activators, such as low concentrations of salicylic acid and citric acid, have been found to have the potential to reduce B. tabaci populations [135]. According to Nadeem et al. [136], whiteflies on okra can be effectively controlled using the systemic pesticide lambda-cyhalothrin 2.5 EC and 4–5% neem oil.

3.4.2. Botanical Control

Neem compounds have been shown to reduce whitefly populations or deter oviposition by exhibiting antifeedant, repellent, and toxic effects [137,138,139,140]. Neem derivatives, particularly neem kernel water extract, are effective against over 350 species of arthropods and significantly reduce B. tabaci damage on okra while increasing yield [141,142]. Applying azadirachtin, a botanical pesticide derived from neem, reduced yellow vein mosaic virus disease incidence and whitefly populations effectively [143]. Azadirachtin, when combined with neem kernel water extract, decreased whitefly damage on okra and increased yield [142,144,145]. Another effective control method is mixing mineral oil with neem or pongamia seed oil [146].

3.4.3. Host Plant Resistance

A cost-effective and efficient method of managing pests is to use resistant crop types [147]. Okra accessions were screened for resistance to whitefly and OYVMV in Tamil Nadu, India [148]. Some accessions, such as GED 545, EC 16394, AE63, IC 22237, IC 18960, and IC 433532, demonstrated resistance to whitefly and OYVMV, whereas other accessions, such as GED 19, GED 11, AE 11, AE 62, AE 64, IC 43743, and Pusa Bhendi 5, were found to be highly resistant to both vector and virus [148].

3.5. Cotton Leafhopper (Amrasca biguttula Ishida (Hemiptera: Cicadellidae))

The cotton leafhopper (Amrasca biguttula Ishida (Hemiptera: Cicadellidae)), also known as jassid, is a significant pest in tropical and subtropical regions, thriving in the favorable year-round environmental conditions, and causes extensive damage to the okra crop, making it one of the most critical sucking insects [149].

A. biguttula nymphs and adults cause damage to the crop by feeding on plant sap, causing phytotoxic symptoms known as ‘hopper burn’, leading to yellowing, browning, bronzing, cupping, withering, and necrosis of leaves, and premature shedding of leaves [150,151]. This results in stunted growth and a decrease in the number, taste, and size of fruits, ultimately leading to reduced yield. Research suggests that the damage caused by this pest can lead to a yield reduction of up to 50.0–63.4% [152]. Additionally, A. biguttula feeding caused a 49.8% reduction in plant height and a 45.1% reduction in leaf size [153].

3.5.1. Chemical Control

Recent research has proven that acetamiprid effectively controls A. biguttula, with minimal impact on natural enemies [154]. Thapa et al. [155] suggested using Neemix^® (Certis Biologicals, Columbia, MD, USA) (azadirachtin) and Justicia sp. as eco-friendly and cost-effective cotton leafhopper control agents.

3.5.2. Cultural Control

Intercropping okra with coriander was proved to reduce leafhopper populations and environmental impact by lessening pesticide use [156,157,158,159].

3.5.3. Microbial Control

Trichoderma spp. serve as synthetic insecticide alternatives, maximizing production [160]. Synthetics show statistical superiority but similar yields to Trichoderma spp. [136,161].

3.5.4. Host Plant Resistance

Okra germplasm derived from Abelmoschus moschatus, A. angulosus, and A. manihot subsp. tetraphyllus displayed higher field resistance to A. biguttula than other tested germplasm [162], with the genotype ‘SabzPari’ showing lower leafhopper populations than ‘Arizona’ [163].

3.6. Cotton Bollworm (Helicoverpa armigera Hübner (Lepidoptera: Noctuidae))

The cosmopolitan and polyphagous cotton bollworm (Helicoverpa armigera Hübner (Lepidoptera: Noctuidae)) is widely distributed in the tropics, subtropics, and temperate regions; poses a threat to various vegetable, fruit, and cereal crops; and is considered one of the most economically significant and widespread insect pests of okra [164]. In fact, among vegetable hosts, okra is the second most important and the most preferred host crop for the feeding and oviposition of this arthropod, next to tomato [164,165]. H. armigera inflicts significant damage on young growing shoots and pods of okra, resulting in decreased yield in terms of quality and quantity [166]. Yield loss in okra crops can range from 35.0 to 40.0%, but under optimal environmental conditions for the pest, the level of damage can escalate to 60.0–70.0% [164,167]. Among vegetable hosts, the survival rate of neonates is comparatively lower on okra due to mucilaginous substances that are exuded from the fruits [168]. External symptoms of fruit borer infestation appear in irregular boreholes on fruits, which are plugged with excreta. This is caused by the fruit borer in larval stages, which directly causes damage to flowers, buds, and fruits [164].

3.6.1. Chemical Control

Chemical insecticides, insect growth regulators, and fourth-generation insecticides have shown effectiveness against lepidopterous pests, with spinosad being notably effective against H. armigera [169,170]. Emamectin benzoate, a broad-spectrum lepidoptericide, disrupts the receptors on the nerve cell membranes of pests, and reduces cotton bollworm damage in okra [171,172]. In another study, treatments with neem oil (0.3%) and azadirachtin 0.15 EC (0.0006%) had the lowest number of larvae of H. armigera and percent fruit damage and obtained maximum fruit yield, followed by neem seed kernel extract (5%) [173].

3.6.2. Microbial Control

The use of Bt has been proven effective in controlling H. armigera. Karim et al. [174] evaluated a locally developed Bt formulation (CAMB) and two commercial formulations, Agree^® (Certis Biologicals, Columbia, MD, USA) (Bacillus thuringiensis subsp. aizawai strain GC-91) and Larvo-BT (B. thuringiensis subsp. kurstaki), in okra fields. All formulations successfully controlled H. armigera larvae, with the CAMB formulation showing efficacy comparable to commercial products, suggesting its potential as an effective alternative in IPM strategies. Malik, Jabeen, et al. [107] analyzed Bt isolates from different ecological regions in Pakistan, finding a wide range of 50.0% lethal concentration (LC50) values. The most potent isolates, HW 4.4 and INS2.25, had an LC50 of 9 ng/mg of artificial diet, indicating high efficacy against H. armigera.

3.6.3. Host Plant Resistance

Resistant cultivars such as ‘KT-458’, ‘Bhindi Punjab’, ‘Arka Anamika’, and ‘Bhindi Sabazpari’ showed less damage by H. armigera, suggesting their potential for cultivation [175].

3.7. Two-Spotted Spider Mite (Tetranychus urticae Koch (Acarida: Tetranychidae))

Tetranychus urticae Koch (Acarida: Tetranychidae), commonly known as the two-spotted spider mite or the red spider mite and formerly as Tetranychus cinnabarinus Boisd., is a highly polyphagous pest that poses a significant threat to various vegetable crops worldwide including okra. This pest feeds on over 900 plant species and severely threatens at least 150 economically important agricultural and ornamental plants [176,177]. Lall and Dutta [178] reported a yield loss of 36.8–83.2% in okra due to spider mites.

The mites produce excessive webbing that covers the entire plant, impeding photosynthesis and transpiration, and may lead to chlorophyll loss, stunting of growth, stippling, leaf yellowing, defoliation, leaf burning, reduction in fruit size and quality, and even death [179]. This pest’s high reproductive potential and extremely short life cycle, combined with frequent acaricide applications, have led to its development of resistance to almost all conventional pesticides in use [180,181]. Furthermore, warm and dry weather conditions are conducive to this pest’s rapid multiplication and spread [179].

3.7.1. Chemical Control

Avermectin, produced by the soil Actinomycete Streptomyces avermitilis, was reported to provide excellent initial and residual control of immature and adult mites on various crops [182]. According to Ghosh [183], fenazaquin, followed closely by avermectin, led in red spider mite suppression.

3.7.2. Biological Control

Various natural predators have been reported to prey on spider mites. Among these, Stethorus sp. coccinellids, Oligota sp. staphylinids, and Amblyseius longispinosus phytoseiids are the primary predators of spider mites [184]. Amblyseius alstoniae and Scolothrips indicus also correlated positively with mite control [185], as did Blaptostethus pallescens against T. urticae, offering acaricide-like efficacy [186,187].

3.7.3. Botanical Control

In a study by Singh et al. [188], pongamia and neem oil contributed to spider mite control. Among the bio-pesticides used in another study, neem and Spilanthes in combination presented good suppression results, recording more than 70.0% mite suppression [183].

3.8. Root-Knot Nematodes (Meloidogyne spp.)

Root-knot nematodes are a major concern in vegetable cultivation and can infect various crops, including weeds, and are particularly difficult to manage due to their high reproductive potential [189]. While there are over 100 known species of Meloidogyne, M. javanica (Treub) Chitwood (Rhabditida: Meloidogynidae), M. hapla Chitwood, M. incognita (Kofold & White) Chitwood, and M. arenaria (Neal) Chitwood are the most common, and they attack more than 2000 species of plants, many of which are cultivated.

Of these nematodes, M. incognita is the most damaging and causes significant economic losses [190]. Globally, M. incognita has been reported as constituting about 47.0% of the total root-knot nematode population [191].

Although yield losses in okra caused by root-knot nematodes can reach 91.0% [192], most estimates range from 10.0% to 29.0%, [193,194]. Root-knot nematodes can also create disease complexes by interacting with specific fungi and bacteria [195]. This leads to the breakdown of resistance against all pathogens, ultimately decreasing plant tolerance to environmental stress [196].

M. incognita has a high reproductive rate, with a single female capable of producing up to a thousand eggs, making control efforts challenging [197,198]. Additionally, M. incognita induces multiple symptoms in okra, such as nutrient deficiency, stunted growth, root galling, leaf browning, suppression of plant growth, fruit yield reduction, and lower photosynthetic pigment levels [199,200].

3.8.1. Botanical Control

Liquid formulations of Azadirachta indica, Cleome viscosa, and Calotropis procera leaf extracts have been shown to improve okra growth and yield, as well as reduce root-knot nematode damage [201,202]. Lantana camara leaf extract, siam weed, neem seeds, and castor leaves also demonstrated nematode control [203,204,205]. Similarly, Targetes erecta and botanical extracts such as cassia and lemon grass can control nematodes [206,207].

3.8.2. Integrated Control

Compost from pequi fruit waste and lemon grass extract has been effective against M. javanica in okra, improving plant health and reducing nematode effects [208,209].

3.8.3. Cultural Control

Fabiyi [210] concluded that Eucalyptus officinalis, as a soil amendment, could manage M. incognita without synthetic nematicides.

3.8.4. Microbial Control

Fungal filtrates of Fusarium oxysporum and Aspergillus flavus significantly reduced nematode populations and supported plant growth [211].

3.8.5. Host Plant Resistance

Studies on intergeneric grafting of okra onto resistant rootstocks offer a prophylactic approach to managing root-knot nematodes through genetic resistance, complementing traditional cultivar development [212]. Resistant cultivars and non-host plants reduced soil nematode populations, with cultivars such as ‘SabzPari 2001’, ‘X Ramakrishna’, and ‘SabzPari’ recommended for root-knot nematode-infested soils [213,214,215]. Similarly, moderately resistant okra cultivars, including ‘Sanam’ and ‘Arka Anamika’, were suggested for root-knot nematode control [216].

3.9. Reniform Nematode (Rotylenchulus reniformis Linford & Oliveira (Rhabditidae: Hoplolaimidae))

The reniform nematode is a significant plant-parasitic nematode that, alongside the southern root-knot nematode, plays a major role in reducing agricultural crop production [217]. Reniform nematodes are responsible for substantial yield losses, which can occur both through direct root feeding and indirectly via interactions with soilborne fungal pathogens, exacerbating plant stress and disease [217].

Roylenchus reniformis Linford & Oliveira (Rhabditidae: Hoplolaimidae)) is predominantly found in tropical and subtropical regions and has a broad host range, affecting key crops such as okra, cotton and various vegetable and field crops, making it a significant threat to diverse agricultural systems [218].

One of the challenges in managing R. reniformis is the subtlety of its symptoms. Unlike M. incognita, which causes noticeable galling on root tissues, R. reniformis does not induce such visible damage [219]. As a result, its presence often goes undetected, with yield losses manifesting in ways that can easily be mistaken for nutrient deficiencies [219].

3.9.1. Cultural Control

Crop rotation, especially the okra–rice–fallow sequence, has proven effective in managing R. reniformis populations, significantly suppressing reniform nematode levels [220]. Soil applications of neem cake at 10 g/kg soil in okra were the most effective among tested organic amendments, significantly reducing nematode populations and enhancing plant growth [221].

3.9.2. Botanical Control

Neem-based urea coatings such as Nimin^® and U-Coat^® also decreased nematode populations in okra by 14.0–25.0% [222].

3.9.3. Microbial Control

Trichoderma species, particularly T. harzianum, T. hamatum, and T. koningii, significantly inhibited nematode activity in okra, reducing female and egg mass numbers [9]. Talc-based formulations of Purpureocillium lilacinum, Pochonia chlamydosporia, and Trichoderma viride in okra also effectively reduced reniform nematode populations at 4.5 g/kg soil [223].

3.9.4. Chemical Control

Seed treatment with 100% avermectin in okra resulted in the highest reductions in nematode populations and improved plant growth [224].

3.10. Cotton Leaf Roller (Syllepte derogata Fabricius (Lepidoptera: Crambidae))

The cotton leaf roller (Syllepte derogata Fabricius (Lepidoptera: Crambidae)), also known by its other scientific name Haritalodes derogata Fabricius, is a dreaded leaf-eating insect that causes significant damage to okra. During the early stages of the okra plant’s growth, this insect pest causes defoliation by feeding voraciously on the leaves [225].

While they feed on the undersides of leaves, the larvae of the cotton leaf concentrate within rolls of leaves, which they secure with silken threads. Moreover, they coat the leaves with webs, aggravating the damage caused by their feeding. As the larvae feed on the leaf margins, they cause the leaves to coil and roll, drastically reducing the photosynthesis-capable leaf area. This can have devastating effects on the health and yield of okra plants, especially during severe infestations when the plants may be entirely defoliated [52,226]. The consequence is poor blooming and fruiting, and a substantial loss in yield [164].

3.10.1. Chemical Control

Atulukwu [227] demonstrated the effectiveness of Ampligo^® (Syngenta, Basel, Switzerland) (chlorantraniliprole 100 g/L + lambda-cyhalothrin 50 g/L) against the leaf roller on okra. Jalgaonkar et al. [228] found 0.05% cypermethrin most effective in reducing leaf damage and boosting yield when applied twice. Similarly, Misra et al. [229] reported high efficacy of cypermethrin against S. derogata.

3.10.2. Botanical Control

Kamaraj et al. [230] tested extracts of Citrus sinensis, Ocimum canum, O. sanctum, and Rhinacanthus nasutus against S. derogata, finding moderate larvicidal effects, with some extracts showing high mortality. Neem seed oil and aqueous extract applications were reported to cause a high suppression of S. derogata, as well as less damage and higher yields in okra, with neem seed oil and aqueous extract applications [52,231]. Adhikary [232] found weekly application of crude neem extracts, especially seed kernel ones, highly effective against Podagrica spp. and S. derogata, increasing yield.

3.10.3. Microbial Control

Bt formulations effectively reduced S. derogata populations [52,233,234,235].

3.11. Flea Beetles (Nisotra uniformis Jacoby (Coleoptera: Chrysomelidae) and N. sjoestedti Jacoby)

Flea beetles (Nisotra uniformis Jacoby (Coleoptera: Chrysomelidae) and N. sjoestedti Jacoby, also known as Podagrica uniformis Jacoby and P. sjoestedti Jacoby, respectively), are recognized as significant agricultural pests that have a detrimental impact on the general condition and productivity of crops, including okra [236]. The adult beetles diminish the plant’s photosynthetic capacity by creating holes in the leaves, resulting in their dehydration and eventual dropping. Meanwhile, the larvae consume the plant’s roots. In addition, these beetles serve as vectors for the okra mosaic virus [237].

3.11.1. Chemical Control

The efficacy of chemical insecticides such as lambda-cyhalothrin has been demonstrated in managing flea beetle infestations in okra [238,239,240,241].

3.11.2. Botanical Control

Various botanical extracts, including Piper guineense (West African black pepper), A. indica (neem), Ocimum basilicum (basil), and Jatropha curcas (Barbados nut) have been recognized as comparatively safer alternatives in the control of flea beetles, although they are generally found to be less efficacious than chemical control [238,239,240,241]. The extract derived from Spondias mombin (yellow mombin), as observed in a study conducted by Adesina and Idoko [242], demonstrated substantial flea beetle suppression and an increase in okra fruit yield.

4. Minor Okra Pests and Their Management Strategies

4.1. Blister Beetles (Mylabris pustulata Olivier (Coleoptera: Meloidae) and M. phalerata Pallas)

Blister beetles (Mylabris pustulata Olivier (Coleoptera: Meloidae) and M. phalerata Pallas) are recognized for causing considerable damage to flower buds, flowers, and, on occasion, fruits or stems. This results in diminished fruit production and substantial crop yield decline, particularly in okra [243,244].

4.1.1. Chemical Control

Anandita and Jayaram [245] observed that cypermethrin exhibited the highest efficacy among the chemical insecticides tested, with a significant reduction of 74.9% in beetle populations.

4.1.2. Microbial Control

The mortality rate of blister beetles caused by B. thuringiensis isolates reached 36.6% [246].

4.1.3. Integrated Control

Singh et al. [247] demonstrated that a combination of chili, garlic, neem leaf extract, and cow urine reduced blister beetle populations by 94.6%.

4.2. Okra Petiole Maggot (Melanagromyza hibisci Spencer (Diptera: Agromyzidae))

Melanagromyza hibisci Spencer (Diptera: Agromyzidae), the okra petiole maggot (or okra stem fly), has become a significant pest that inflicts substantial damage to the primary stems of young okra plants. This damage manifests as noticeable swelling of the stems and, in some cases, can result in the death of the plant, particularly during the winter cropping season. The larvae are widely recognized for their tendency to selectively feed on seedlings, resulting in the formation of galls and impeding the normal growth process [248].

4.2.1. Biological Control

The inherent occurrence of Eurytoma sp., a parasitoid to the petiole maggot, demonstrated potential as a biological control agent against M. hibisci [248].

4.2.2. Integrated Control

Field experiments led by Moorthy and Kumar [249] were conducted to determine the effect of soil application of oiled neem cake (NC) and sprays of 1% neem soap (NS) and 4% neem seed powder extract (NSPE) on the incidence of petiole maggot. The treatments significantly reduced okra petiole maggot infestation. The combination of soil application of NC with sprays of NS and NSPE was consistently more effective in reducing petiole maggot incidence compared with solo treatments.

4.3. Red Cotton Bug (Dysdercus koenigii Fabricius (Hemiptera: Pyrrcohoridae))

The red cotton bug (Dysdercus koenigii Fabricius (Hemiptera: Pyrrcohoridae)), a primary member of the Pyrrhocoridae family, is well known as a significant pest of cotton, its primary host, but it can also affect okra [250,251,252,253].

Botanical Control

Shahzad et al. [254] conducted a study evaluating the efficacy of Eucalyptus extract in managing Dydercus cingulatus on okra, in which the extract achieved a 65.0% mortality rate, outperforming Naas boo and lambda-cyhalothrin, which resulted in 35.0% mortality. These results highlight the significant potential of Eucalyptus extract as an effective alternative for controlling D. cingulatus in okra cultivation. Shukla et al. [255] reported that sweet flag (Acorus calamus) and nirgundi (Vitex negundo) extracts significantly reduced D. koenigii populations on okra under field conditions, achieving mortality rates of up to 100% and 93.3%, respectively, demonstrating their potential as pest management solutions.

4.4. Cotton Seed Bug (Oxycarenus hyalinipennis A. Costa (Hemiptera: Oxycarenidae))

The cotton seed bug (Oxycarenus hyalinipennis A. Costa (Hemiptera: Oxycarenidae)) poses a severe threat to cotton and okra crops by sucking fluid from tender stems and oil from mature seeds [256]. This results in a significant decrease in seed weight, oil content, and overall cotton and okra yield. This infestation damages the seed embryo, making germination less likely [257].

Botanical Control

Research has demonstrated the effectiveness of plant extracts such as neem extract in controlling O. hyalinipennis, as it outperformed malathion in controlling the bug, especially 72 h after treatment [258], while tobacco and milkweed extracts showed considerable mortality rates of up to 97.0% and 89.0%, respectively [259].

4.5. Cotton Looper (Anomis flava Fabricius (Lepidoptera: Erebidae))

Okra, as well as other crops such as cotton, is impacted by the cotton looper, Anomis flava Fabricius (Lepidoptera: Erebidae) [260]. Most A. flava eggs are deposited on the undersides of leaves. The young larvae skeletonize the leaves [261,262]. In high numbers, A. flava larvae can cause significant damage by destroying the leaves, shoots, and buds of okra and other Malvaceous crops [263].

4.5.1. Biological Control

The natural enemies of A. flava include egg parasitoids such as Trichogramma spp. [264,265], larval parasitoids such as Apanteles anomidis [266], and pupal parasitoids such as species of Brachymeria [267].

4.5.2. Microbial Control

Microbial agents such as B. thuringiensis [268] have shown promise in controlling A. flava. Predators, including pentatomid and carabid beetles, as well as Indian mynah birds, also play a role in managing A. flava populations [269]. Further research into additional control methods for this insect should be explored.

4.6. Onion Thrips (Thrips tabaci Lindeman (Thysanoptera: Thripidae))

Onion thrips (Thrips tabaci Lindeman (Thysanoptera: Thripidae)) is a polyphagous pest that poses a significant threat to onions and other crops such as garlic, cotton, and okra. In addition to its direct damage, it acts as a vector of different diseases. The feeding method of this pest results in leaf scarring or silvering, causing significant damage as the plant grows [270].

4.6.1. Botanical Control

Plant extracts, such as neem and garlic, have the potential to reduce thrips population, with neem being especially effective in enhancing okra pod yield [271].

4.6.2. Cultural Control

Adopting wider plant spacing reduces thrips density and improves bulb weight [272]. Monitoring tools, such as blue and yellow sticky traps, have been effective in attracting thrips. Blue traps are more selective, while yellow traps work well in subtropical climates [273,274].

4.7. Green Plant Bug (Nezara viridula Linnaeus (Hemiptera: Pentatomidae))

The green plant bug (Nezara viridula Linnaeus (Hemiptera: Pentatomidae)), also known as southern green stink bug, is a polyphagous pest that causes significant damage and reduces crop yields by extracting cell content from plants [275].

4.7.1. Botanical Control

Pramudi, Febrianti, et al. [275] emphasize garden spurge (Euphorbia hirta) extract’s potential as a biopesticide against N. viridula. Azhari et al. [276] showed the effectiveness of the fungus Metarhizium anisopliae on the incubation period, mortality, and death time of N. viridula and in its management with a concentration of 8 g/100 mL.

4.7.2. Chemical Control

Abudulai et al. [277] found that Neemix^® 4.5 EC, an azadirachtin formulation, reduced feeding in adult N. viridula, while highlighting the potential of the sterile insect technique for the insect’s control.

4.8. Lesion Nematode (Pratylenchus brachyurus Godfrey (Rhabditida: Pratylenchidae))

Root lesion nematodes are a significant group of plant-parasitic nematodes that affect a wide variety of crops [278]. Pratylenchus brachyurus Godfrey (Rhabditida: Pratylenchidae) is particularly recognized for causing lesions on potato tubers and being a minor pest of okra [278,279,280,281].

Root lesion nematodes are migratory endoparasites that primarily feed on the root cortex of plants [282]. This feeding activity leads to the formation of lesions that turn the affected root tissues brown to yellow [282]. As lesion nematodes move through the root cortex, they create channels that can be easily observed in longitudinal sections of the roots [282]. These channels disrupt the normal functioning of the roots, impeding their ability to absorb water and nutrients effectively, which can cause stunted growth, chlorosis, and wilting, particularly under stress conditions [282]. This damage is often exacerbated by the nematode’s role in predisposing plants to secondary soil-borne pathogens, further compromising plant health [278].

Cultural Control

Compost amendments have been shown to suppress P. brachyurus populations by up to 67.3% in roots and 59.2% in soil, while promoting plant health through the presence of beneficial microorganisms such as Trichoderma spp. [283].

5. Oomycete and Fungal Diseases of Okra, and Their Management Strategies

Table 2. Most common oomycete and fungal diseases of okra, their causative organisms, and main symptoms.

Disease	Causative Fungi	Symptoms	Refs.
Damping-off	Pythium aphanidermatum (Edson) Fitzpatrick Rhizoctonia solani Kühn Fusarium solani (von Martius) Saccardo) Macrophomina phaseolina (Tassi) Goidanich Phytophthora nicotianae Breda de Haan	Water-soaked lesions at the stem collar region. Browning and shrinkage of the stem tissue and seedling collapse.	[284].
Powdery mildew	Golovinomyces cichoracearum (de Candolle) Heluta	White to grayish-white powdery fungal growth on leaves, stems, and occasionally flowers or fruits. Leaf deformation, curling, yellowing, and stunted plant growth.	[285].
Cercospora leaf spot	Cercospora malayensis Stevens & Solheim C. abelmoschi (Ellis & Everhart) Deighton	Irregular brown or black spots on mature leaves, developing into reddish-brown with yellow margins, expanding and reducing photosynthesis.	[15,286].
Gray mold	Botrytis cinerea Persoon	Grayish, web-like fungal growth on leaves, stems, and fruits. Light brown lesions on thin leaves, concentric brown rings on thicker leaves. Wilting in severe cases.	[287].
Alternaria leaf spot	Alternaria alternata (Fries) Keissler A. chlamydospora Mouchacca	Small, light brown-concentric dark brown lesions on the leaves. Necrosis, wilting, and plant death under severe infections.	[288,289,290].
Alternaria pod blight	Alternaria alternata (Fries) Keissler	Wet rot on young okra pods, development of lesions, leading to decay.	[291].
Phyllosticta leaf spot	Phyllosticta hibiscini Ellis & Everh.	Large leaf lesions with a grayish center, progressing to form shot holes. Presence of black pycnidia on both leaf surfaces.	[292].
Fusarium wilt	Fusarium oxysporum f. sp. vasinfectum sensu lato (Atkinson) Snyder & Hansen	Leaf discoloration and wilting, stunted growth, vascular damage, and stem deterioration, leading to wilting and death.	[293,294].
Verticillium wilt	Verticillium dahliae Klebahn V. tricorpus Isaac	Initial symptoms include yellowing followed by wilting and drying, V-shaped chlorosis of leaflets, and yellow-to-red-brown lesions near the leaf tip. Severe infections lead to defoliation, shoot dieback, and plant death.	[295,296].
Collar rot	Macrophomina phaseolina (Tassi) Goidanich	Damping-off, seedling blight, collar rot, stem rot, and root rot in mature plants. Hollow stem formation, pre-emergence and post-emergence damping-off.	[297].
Stem canker	Fusarium chlamydosporum sensu lato Wollenweber & Reinking	Dark circular to oblong lesions on the stems, floral buds, and pods of young plants. Severe infections lead to seedling death.	[298].
Anthracnose	Colletotrichum plurivorum Damm, Alizadeh & Toy. Sato C. gloeosporioides (Penzig) Penzig & Saccardo	Yellow-brown, necrotic, sunken lesions on the leaves.	[299,300].
Fruit rot	Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter Rhizoctonia solani Kühn Fusarium solani (von Martius) Saccardo Phytophthora palmivora E.J. Butler Rhizopus stolonifera (Ehrenberg) Vuillemin Fusarium oxysporum Schlechtendal Aspergillus flavus Link	Brown-black water-soaked lesions on fruits, progressing rapidly and causing fruit decay and drop.	[301,302,303].

provides an overview of the predominant oomycete and fungal diseases impacting okra, listing the symptoms and the specific pathogens responsible for each disease.

5.1. Damping-Off

Damping-off is a common crop disease that causes the deterioration of germinating seeds and seedlings pre- and post-emergence. Affected seedlings display symptoms such as water-soaking, browning, and shriveling at the stem’s collar region, leading to toppling [284]. The main pathogens causing this disease in okra are oomycetes and fungi, including Pythium aphanidermatum (Edson) Fitzpatrick (Pythiales: Pythiaceae), Rhizoctonia solani Kühn (Ceratobasidiales: Ceratobasidiaceae), Fusarium solani (von Martius) Saccardo (Hypocreales: Nectriaceae), Macrophomina phaseolina (Tassi) Goidanich (Botryosphaeriales: Botryosphaeriaceae), and Phytophthora nicotianae Breda de Haan (Peronosporales: Peronosporaceae) [284,304]. R. solani, a soil-dwelling fungus, is highly destructive [305]. P. aphanidermatum is a significant pathogen that thrives under specific temperature and humidity conditions [306].

Environmental factors, such as cool, cloudy weather, high humidity, and compacted soils exacerbate damping-off symptoms [15]. The disease can manifest as pre-emergence damping-off, where seeds rot before emerging, and post-emergence damping-off, particularly severe during the cotyledonous stage of seedlings [284].

5.1.1. Chemical Control

Non-systemic fungicides, including copper oxychloride and captan, are commonly employed for damping-off protection [307,308].

5.1.2. Microbial Control

Microbial control methods show promise as alternatives. Trichoderma spp., isolated from okra rhizosphere soil, exhibit antagonistic activity against R. solani, preventing damping-off disease damage [309]. Pseudomonas fluorescens effectively counters damping-off when applied to soil or as a seed coating [310], with T. viride, Aspergillus terreus, and Bacillus subtilis also showing antifungal properties [311,312,313].

5.1.3. Botanical Control

Botanical extracts can aid in disease control. Garlic bulb extract, basil leaf water extract, and T. harzianum culture filtrate have all inhibited the growth of damping-off organisms in okra [312,314].

5.1.4. Integrated Control

In a study by Jabur [315], a combination of B. subtilis, garlic (Allium sativum) extract, and Ridomil^® fungicide (Syngenta, Basel, Switzerland) (metalaxyl) effectively controlled P. aphanidermatum-induced damping-off.

5.2. Powdery Mildew

Powdery mildew, predominantly attributed to Golovinomyces cichoracearum de Candolle) Heluta (Erysiphales: Erysiphaceae) (formerly known as Erysiphe cichoracearum), poses a substantial threat to okra cultivation, resulting in considerable financial losses [316]. The sign of the disease is characterized by the presence of a powdery mycelium and spores, ranging in color from white to grayish-white, on various plant parts such as leaves, stems, and rarely flowers or fruits. Common symptoms associated with this disease include the deformation and formation of blisters on the leaves [285].

5.2.1. Botanical Control

Plant-derived antifungals, including cold-water extracts of papaya leaves and botanical extracts from A. indica and A. sativum, have demonstrated effectiveness in controlling G. cichoracearum [15,317].

5.2.2. Microbial Control

Bioagents, such as Trichoderma and Ampelomyces quisqualis, have been identified as promising control measures. A. quisqualis, in particular, has been acknowledged for its natural hyperparasitic properties against powdery mildew [318].

5.2.3. Chemical Control

The use of chemical control methods continues to be a fundamental approach against powdery mildew. According to Naik and Nagaraja [319], Topas^® (Syngenta, Basel, Switzerland) (penconazole) at a concentration of 0.1% was effective in the control of powdery mildew. Previous research has indicated that wettable sulfur at a concentration of 0.2% exhibited efficacy as a fungicide against the disease [320].

5.2.4. Integrated Control

The utilization of a combination of difenoconazole and A. indica extract has been proposed as a potential strategy for improving management of powdery mildew, as reported by Ashfaq et al. [321].

5.2.5. Host Plant Resistance

A study conducted by Zaher et al. [322] found promising results in utilizing the resistant ‘Japanese’ okra cultivar and the moderately resistant ‘Hendi’ cultivar to manage powdery mildew.

5.3. Cercospora Leaf Spot (Cercosporiosis)

Cercospora leaf spot, also known as Cercosporiosis, caused by Cercospora malayensis Stevens & Solheim (Mycosphaerellales: Mycosphaerellaceae), is a major fungal disease affecting okra, resulting in yield losses of up to 60.0% [286]. The disease presents as irregular brown spots on mature leaves, which may develop a reddish-brown coloration with a yellow margin. As the disease advances, the spots can expand, leading to complete leaf necrosis [286]. Cercospora abelmoschi (Ellis & Everhart) Deighton, another species, also contributes to this disease, characterized by initial symptoms in the form of black angular spots. Both pathogens are commonly found in tropical and subtropical regions, particularly during rainy seasons [15].

5.3.1. Microbial Control

Alexis et al. [323] investigated a formulation combining Trichoderma harzianum and Bacillus amyloliquefaciens for enhancing germination and controlling Cercosporiosis of okra. This formulation significantly increased seed germination (up to 94.4%) and provided effective protection (77.8% to 100%) against the disease across different growing conditions. Additionally, treated okra leaves showed higher levels of bioactive compounds, indicating enhanced systemic resistance.

5.3.2. Chemical Control

Tebuconazole exhibited potent fungicidal activity, effectively suppressing the fungal growth of C. malayensis. In field conditions, the application of tebuconazole (0.1%) three times via foliar spray resulted in the highest seed germination, lowest disease incidence, and maximum fruit yield [324].

5.3.3. Host Plant Resistance

Certain okra varieties, specifically ‘Local 2’ and ‘Local 2 (P)’, have demonstrated increased field resilience against Cercospora leaf spot, indicating their potential suitability for breeding programs focused on improving disease resistance [325].

5.4. Gray Mold

Botrytis cinerea Persoon (Helotiales: Sclerotiniaceae) causes gray mold, an important disease that impacts a wide range of crops, including okra [326]. This necrotrophic pathogen exhibits a broad host range, capable of infecting diverse plant organs, ranging from foliage to reproductive structures, thereby resulting in significant worldwide agricultural yield reductions annually [327]. The disease manifests with the presence of grayish mycelium, characterized by a web-like appearance, particularly in conditions of high humidity. Lesions of a light brown hue manifest on thin leaves, whereas on thicker leaves, the formation of concentric brown rings may occur [287].

Although B. cinerea has a broad host range, its specific effects on okra have not been extensively studied. A research investigation carried out in Korea documented the manifestation of gray mold symptoms in approximately 5.0% of the okra fruit [287].

Chemical Control

Chemical control continues to be a predominant approach in combating B. cinerea. In a study conducted by Wang et al. [328], the application of sodium dehydroacetate and trans-2-hexenal exhibited significant inhibitory effects on the growth of B. cinerea, with the treated crops demonstrating a notable reduction in disease progression while concurrently maintaining elevated nutrient levels.

5.5. Alternaria Leaf Spot

Okra is susceptible to Alternaria leaf spot, predominantly caused by Alternaria alternata (Fries) Keissler (Pleosporales: Pleosporaceae) and A. chlamydospora Mouchacca (Pleosporales: Pleosporaceae). Reducing yields by 30.0–50.0% or more, this disease causes significant quantitative and qualitative losses in the production of okra [25,329]. Light brown patches on leaves initially appear as symptoms, eventually developing into concentric dark brown spots of different sizes. These spots may eventually cover large sections of the leaf as the disease worsens, in which case the leaves may wilt, leading to the death of the plant [288,289,290].

Botanical Control

Botanical control approaches to Alternaria leaf spot have also been investigated. Essential oils from plants, such as neem and garlic, have the ability to inhibit Alternaria species [330,331,332]. Similarly, significant inhibitory effects were seen in extracts obtained from A. indica leaves and A. sativum bulbs, with 74.4% and 70.7% inhibition, respectively [333].

5.6. Alternaria Pod Blight

The pathogen that is responsible for the occurrence of Alternaria rot in okra pods has been identified as Alternaria alternata, causing a post-harvest disease. A notable occurrence of wet rot in juvenile okra pods was observed, prompting subsequent investigations that successfully identified A. alternata as the causative pathogen. This finding signifies the initial record of wet rot occurrence on okra in Egypt [334]. Additional research conducted in Japan sought to elucidate the correlation between storage conditions and the incidence of Alternaria rot on okra pods [291]. The occurrence of lesions exhibited a decrease when exposed to temperatures below 15 °C and was nearly non-existent under conditions of elevated carbon dioxide and anaerobicity with 20.0% CO₂ (0% O₂) [291]. A worsening of Alternaria rot in okra pods was observed when stored in environments with a relative humidity of 100%. However, the disease was mitigated when conditions of 50.0–90.0% relative humidity and temperatures above the dew point were maintained [291].

Alternaria pod blight management remains under-researched, highlighting the need for research on effective control strategies.

5.7. Phyllosticta Leaf Spot

While not as widespread as Cercospora leaf spot or Alternaria leaf spot, okra plants can display leaf spots caused by Phyllosticta hibiscini Ellis and Everh (Botryosphaeriales: Phyllostictaceae). These lesions, distinguished by their conspicuous size and initial grayish center, ultimately result in the formation of shot holes. Pycnidia, observed as minute black specks, are discernible on both sides of the leaf. It is essential to acknowledge that there is an absence of comprehensive scientific investigation about this pathogen [292].

The control and management of Phyllosticta leaf spot remains largely unexplored, underscoring the critical need for in-depth research to develop effective control strategies for this fungal disease.

5.8. Wilt Diseases

5.8.1. Fusarium Wilt

Fusarium wilt is a major disease of okra, resulting in significant yield reduction [335]. It is caused by the Fusarium oxysporum Schlechtendal (Hypocreales: Nectriaceae) species complex (FOSC), which comprises several cryptic species, with its taxonomy evolving due to molecular advances. The causal agent of Fusarium wilt in okra has traditionally been referred to as Fusarium oxysporum f. sp. vasinfectum sensu lato, which is no longer recognized under modern taxonomic criteria. Recent studies have reclassified isolates previously identified as F. oxysporum f. sp. vasinfectum into three distinct species: F. gossypinum, F. triseptatum, and F. cugenangense [336,337]. The exact identification of the pathogen causing Fusarium wilt in okra has not been clarified or updated.

F. oxysporum is cosmopolitan in distribution, is both seed-borne and soil-borne, produces chlamydospores and macro- and micro-conidia, and is considered one of the most important fungi present in a wide range of soils [338,339]. The fungus infects plants through their roots, subsequently spreading to the vascular system [293]. The initial symptoms encompass leaf discoloration and distortion. As the infection progresses, the plant demonstrates inhibited growth, alterations in its vascular system, and deterioration of its stem, ultimately resulting in the plant’s death [293,294].

Microbial Control

Trichoderma harzianum, specifically the ‘Th-Sks’ isolate, effectively suppresses F. oxysporum in okra, achieving a 96.4% reduction in the disease under greenhouse conditions [340].

Botanical Control

Neem, citrus leaves, and garlic bulb extracts have demonstrated effectiveness against F. oxysporum under both in vitro and in vivo conditions, with higher concentrations of neem and garlic extracts exhibiting notable efficacy [341].

Host Plant Resistance

In a study assessing different okra varieties against Fusarium wilt, no complete immunity against F. oxysporum was observed. However, certain varieties such as ‘Arka Abhay’ and ‘Aruna’ exhibited lower incidences of Fusarium wilt, indicating a degree of resistance [342]. A study conducted on 260 okra plant accessions revealed that only 9 exhibited resistance to Fusarium wilt [343]. In a study by Aguiar et al. [344], 54 okra accessions were evaluated against F. oxysporum. Among these accessions, ‘Santa Cruz-47’, ‘BR-2399’, and ‘BR-1449’ were identified as the most promising sources of resistance. However, the need for a more precise identification of Fusarium species associated with Fusarium wilt of okra remains critical. The accurate identification of the causal agent is essential for developing effective and targeted management strategies, including the development of resistant varieties.

5.8.2. Verticillium Wilt

Verticillium wilt, a fungal disease caused by Verticillium dahliae Klebahn (Glomerellales: Plectosphaerellaceae) and V. tricorpus Isaac, has emerged as an important problem. Over 200 plant species, including many economically important agricultural crops, are infected by V. dahliae [345]. Initially, leaves of infected plants turn from light green to yellow, and eventually become wilted and dry. Over time, these factors can result in defoliation, shoot dieback, and plant mortality [295,296]. In the warmer periods of summer days, leaves experience a loss of turgor, causing the leaf margins to roll upwards. However, partial recovery is possible when the temperature decreases during the night. Additional symptoms include V-shaped chlorosis of leaflets, yellow-to-red-brown lesions near the leaf tip, and, in severe instances, browning of the internal tissues of the petioles and pedicels, leading to plant wilting and death [346].

The discovery of the pathogenicity of V. tricorpus on okra was novel [346]. However, V. dahliae is a well-established pathogen on various plant species. This fungus forms microsclerotia within infected plant tissues, which are able to persist in the soil for a period exceeding 15 years [296,347].

Host Plant Resistance

In a study by Tok et al. [348], all 18 okra cultivars studied were found to be susceptible to V. dahliae, while the ‘Çorum’, ‘Hatay Has’, and ‘Şanlıurfa’ cultivars exhibited the lowest susceptibility, emphasizing the significance of developing resistant okra cultivars for sustainable production.

Additional research on the control of Verticilium wilt of okra is urgently required.

5.9. Collar Rot

Collar rot, also called charcoal rot, is a significant disease of okra caused by Macrophomina phaseolina (Tassi) Goidanich (Botryosphaeriales: Botryosphaeriaceae). The pathogen’s broad host range is demonstrated by its capacity to affect approximately 500 plant species spanning over 100 plant families worldwide [349]. The adaptability of this organism is attributed to its variability in physiology, morphology, pathogenicity, and genetics, enabling it to cause disease in various agro-ecological zones [350]. M. phaseolina predominantly exists as a soil-borne pathogen and can also be transmitted from infected seeds to seedlings [351].

The disease presents itself in different forms, including damping-off, seedling blight, collar rot, stem rot, and root rot. The fungus efficiently invades host roots at an early stage, and symptoms are only noticeable in mature plants [297]. In addition, warm summer weather can lead to the development of hollow stems, root rot, and both pre-emergence and post-emergence damping-off [352,353]. The severity of the disease worsens as air and soil temperatures rise, especially within the range of 28 to 35 °C. Additionally, limited soil moisture further exacerbates the disease severity [297].

5.9.1. Microbial Control

T. harzianum and Penicillium spp. have demonstrated efficacy in suppressing M. phaseolina, stimulating seed germination, and improving overall plant growth [354,355]. Aravind and Brahmbhatt [356] assessed treatments for managing root and collar rot in pot-grown okra plants. The most effective treatment was seed treatment with T. viride combined with soil application of T. viride enriched with farmyard manure (FYM), resulting in the lowest disease incidence (26.6%) and the highest plant vigor index.

5.9.2. Host Plant Resistance

Okra genotypes ‘AOL-15-23’ and ‘AOL-15-21’ have demonstrated resistance against collar rot caused by M. phaseolina, indicating their potential suitability for breeding disease-resistant commercial cultivars [357].

5.10. Stem Canker

Fusarium chlamydosporum Wollenweber & Reinking (Hypocreales: Nectriaceae) species complex (FCSC) has been recognized as the main pathogen responsible for stem canker in okra. The fungal agent was identified as the cause of significant stem canker outbreaks in okra in India [298]. This observation was supported by later research conducted in the Konkan region of India [358]. The taxonomy of Fusarium remains complex and continues to evolve. F. chlamydosporum is recognized as a species complex comprising several cryptic species. Consequently, the causal agent of stem canker in okra has not been precisely identified, and an updated classification is essential.

Young okra plants exhibit clear dark circular to oblong marks on their stems, which frequently result in seedling death. When the level of humidity and rainfall increased, many plants experienced a break in their bark, which resulted in the underlying cortex being exposed. In addition, there were visible darkened marks on leaf stems, floral buds, and young pods, indicating the presence of infection [298].

There is a significant gap in the literature regarding practical management approaches and control methods for stem canker on okra, hindering efforts to mitigate its impact on crop yield and quality. Future research should prioritize developing integrated management strategies for this disease.

5.11. Anthracnose

Anthracnose, caused by Colletotrichum plurivorum Damm, Alizadeh & Toy. Sato (Glomerellales: Glomerellaceae), C. gloeosporioides (Penz.) Penz. & Sacc, and C. fioriniae (Marcelino & Gouli) Pennycook, presents itself as yellow-brown, necrotic, and sunken lesions on the leaves, causing a substantial negative effect on both the quantity and quality of the crop [299,300]. Disease incidence in a study in Brazil reached 60.0% [359].

Botanical Control

A study by Zhang et al. [360] found that thymol edible coating (TKL) effectively controlled okra anthracnose caused by C. fioriniae. TKL inhibited fungal growth and damaged cell structures and reduced infection and mycelium growth on okra. Treated okra showed increased phenols, flavonoids, and lignin, enhancing plant defenses. In another study, the efficacy of five plant extracts (neem seed, garlic clove, ginger rhizome, bitter leaf, balanite) was assessed against okra anthracnose. Results demonstrated that neem seed and ginger rhizome extracts significantly reduced disease incidence (20.0% and 18.5%, respectively) at 3 weeks after planting, compared with untreated plots (29.3%) [361].

5.12. Fruit Rot

Okra experiences fruit rot caused by several fungal pathogens. These include Choanephora cucurbitarum (Berkeley & Ravenel) Thaxter (Mucorales: Choanephoraceae), Rhizoctonia solani, Fusarium solani, F. oxysporum, Phytophthora palmivora E.J.Butler (Peronosporales: Peronosporaceae), Rhizopus stolonifer (Ehrenberg) Vuillemin (Mucorales: Mucoraceae), and Aspergillus flavus Link (Eurotiales: Trichocomaceae) [299,301]. The symptoms of fruit rot in okra include the development of lesions, which are often water-soaked and can vary in color from brown to black. These lesions can lead to rapid fruit decay, impacting both the quality and quantity of the harvest. In severe cases, the infection can lead to fruit drop and a significant reduction of up to 50.0% in plant vigor and yield [301,302,303].

Choanephora cucurbitarum has been found to be a significant causal agent of fruit rot in okra. In Nigeria, Esuruoso et al. [362] documented the occurrence of the pathogen, along with F. solani, P. palmivora, and R. solani. Park, Cho, et al. [302] identified C. cucurbitarum as the causative agent of blossom blight and pod soft rot in Korea. This pathogen initiates infection on withered flower petals. In their study, Hussein and Ziedan [363] conclusively identified this fungus as the primary factor responsible for the decay of okra in Egypt. Henz, Lopes, et al. [303] in Brazil emphasized the involvement of R. solani in the development of okra pod rot, specifically in environments with elevated humidity and temperatures of 25 °C. The ability of the fungus to flourish in moist conditions and disseminate through contaminated soil or trash was observed.

There is a significant lack of studies focused on developing comprehensive and effective control and management strategies for okra fruit rot caused by the aforementioned pathogens. Thus, further research is needed.

6. Viral Diseases of Okra and Their Management Strategies

Table 3. Viral diseases and associated causative agents documented on okra.

Disease	Causative Agent	Synonyms	Symptoms	Refs.
Okra yellow vein mosaic disease (YVMV)	Begomovirus abelmoschusflavi	Bhendi yellow vein India virus, bhendi yellow vein mosaic begomovirus, bhendi yellow vein mosaic virus, okra yellow vein mosaic agent, okra yellow vein mosaic virus	Vein yellowing, followed by yellowing of the entire leaf. Reduced fruit size, pale yellow or whitish fruits, and deformation. Stunted plant growth.	[367,368].
Bhendi yellow vein haryana virus (BYVHV)	Begomovirus abelmoschusharyanaense
Okra yellow mosaic Mexico virus (OkYMMV)	Begomovirus abelsmoschusmexicoense		Irregular yellow patches of leaves, distinctive yellow borders on leaf edges, and chlorosis of newly developing leaves.	[369].
Okra enation leaf curl disease (OELCV)	Begomovirus abelsmoschusenation	Okra enation leaf curl virus	Upward curling of leaves with thickened texture, with pin-shaped enations on the underside of leaves. Stunted and distorted plants., with deformed and discolored fruits.	[370].
Okra leaf curl disease (OLCV)	Okra leaf curl virus (OLCV)	Okra leaf curl begomovirus
Okra leaf curl Cameroon virus (OLCuCMV)	Begomovirus gossypigeziraense	Cotton leaf curl Gezira begomovirus, cotton leaf curl Gezira virus, hollyhock leaf crumple virus, okra leaf curl Cameroon virus	Severe leaf curling with margins curling upward. Leaf distortion leading to crinkled and leathery textures. Development of yellow-green mosaics or chlorotic patterns. Stunted plant growth with reduced leaf and plant size, with the production of small, deformed fruits.	[371].
Okra leaf curl Oman virus (OLCOV)	Begomovirus abelsmoschusomanense		Leaf curling, inter-veinal yellowing, vein thickening, and reduced leaf size.	[372].
Okra yellow crinkle virus (OkYCV)	Begomovirus abelsmoschusretorridi	Okra yellow crinkle virus	Vein thickening in affected leaves, curling, distortion, and yellow crinkling of leaf tissues. Stunted plant growth and reduced vigor.	[371].
Cotton leaf curl disease (CLCuD)	Begomovirus gossypialabadense	Cotton leaf curl Alabad virus	Leaf curling, vein swelling or thickening, interveinal chlorosis, plant stunting, leaf crumpling and deformation, and reduced flowering and fruit production.	[371].
Cotton leaf curl Multan virus (CLCuMuV)	Begomovirus gossypimultanense	Cotton leaf curl Multan begomovirus, cotton leaf curl Rajasthan begomovirus, cotton leaf curl Rajasthan virus	Curled and crumpled leaves, thickened and distorted veins, yellow or greenish mosaic patterns on leaves, stunted plant growth with premature defoliation.	[371].
Sida micrantha mosaic virus (SiMMV)	Begomovirus sidamicranthae		Chlorotic spots distributed in a mosaic pattern, interspersed with green streaks. Random alternation of chlorotic and green areas, not confined to veins. Severe stunting in young plants, and localized symptoms in single branches of mature plants.	[373].
Bitter gourd yellow vein virus (BGYVV)	Begomovirus solanumdelhiense	Tomato leaf curl New Delhi begomovirus (ToLCNDV), tomato leaf curl New Delhi virus	Yellowing along the leaf veins, with yellow blotches on the leaf surface.	[374].
Okra mosaic disease (OkMV)	Tymovirus abelmoschi	Okra mosaic tymovirus	Yellowish mottling of plants, stunting and reduced yield, smaller leaves, fruit discoloration, distortion, and abortion.	[375].
Cotton anthocyanosis virus (CAV)	Cotton anthocyanosis virus (CAV)		Excessive purple or reddish pigmentation in lower and medium leaves.	[376].
Tomato chlorosis virus (ToCV)	Crinivirus tomatichlorosis	Tomato chlorosis closterovirus, tomato chlorosis crinivirus	Interveinal chlorosis with green veins, brittleness of leaves, necrotic flecking or bronzing on leaves.	[377].
Tomato spotted wilt virus (TSWV) *	Orthotospovirus tomatomaculae	Tomato spotted wilt orthotospovirus, tomato spotted wilt tospovirus	Chlorosis of plant tissues, necrosis of leaves, stems, and fruits. Stunting of plants, and death in severe cases.	[378].
Radish leaf curl virus (RALCV)	Radish leaf curl virus (RALCV)		Leaf curling, stunted growth, absence of fruit production.	[379].

*: Experimental only.

summarizes the viral diseases reported in okra, their symptoms, and their associated causative agents. Most of these viruses belong to the Begomovirus genus within the Geminiviridae family and are predominantly transmitted by the whitefly species B. tabaci through a persistent, circulative transmission mechanism. These viruses have multiple hosts, with infection sources originating from both wild and cultivated plants [364]. The frequent co-occurrence of begomoviruses with satellite viruses further amplifies the diversity of symptoms observed in host plants [27,365,366]. The most important are okra yellow vein mosaic disease, okra enation leaf curl disease, and okra mosaic disease [29].

6.1. Okra Yellow Vein Mosaic Disease

Okra yellow vein mosaic disease (YVMV), transmitted by the whitefly species B. tabaci, is the most frequently reported viral disease of okra, known by different names in various regions of the world (Table 3) [29,31]. The causative agent of this disease is Begomovirus abelmoschusflavi (Geplafuvirales: Geminiviridae), although several other Begomovirus species, such as B. abelmoschusharyanaense and B. gossypialabadense, have also been associated with leaf yellow vein symptoms [380].

B. abelmoschusflavi has a relatively narrow known host range; besides okra, it has only been reported in Indian laurel (Litsea glutinosa) and Indian valerian (Valeriana jatamansi) [31]. However, it is believed that other cultivated and wild plant species may also be susceptible to infection and could serve as potential sources of the virus [29].

The initial characteristic infection symptom is vein yellowing, followed by the yellowing of the entire leaf. Infected plants often exhibit reduced fruit size and number, with fruits becoming pale yellow or whitish and deformed. In addition, infected plants may become stunted, leading to yield losses ranging from 50.0% to 100% [367,368].

6.2. Okra Enation Leaf Curl Disease

Over the past decade, the prevalence of okra enation leaf curl disease (OELCV) has notably increased, with Kumar et al. [381] reporting a disease incidence ranging from 5.0% to 74.0% in India. The causative pathogen, Begomovirus abelmoschusenation (Geplafuvirales: Geminiviridae), has been shown by Venkataravanappa et al. [382] to have a relatively narrow host range, primarily infecting two species in the family Malvaceae—okra and hollyhock (Althaea rosea)—as well as seven species in the family Solanaceae. However, Saeed et al. [383] found that B. abelmoschusenation can co-infect and trans-replicate with cotton leaf curl Multan satellites in cotton, leading to more severe symptoms and potentially higher yield losses.

Moreover, OELCV has been associated with both alpha- and beta-satellites, as documented by Venkataravanappa et al. [384] and Chandran et al. [385]. This association suggests a complex interaction that may enhance the pathogenicity of the virus. According to Gupta et al. [386], additional begomoviruses and satellites can further contribute to the development of enation leaf curl symptoms, which typically include upward curling of the leaves, thickening of the leaf texture, and the formation of pin-shaped enations on the underside of the leaves. Consequently, infected plants often become stunted and distorted. The fruits also exhibit symptoms similar to those caused by okra yellow vein mosaic virus, such as deformities and discoloration [370].

6.3. Okra Mosaic Disease

A survey of the literature indicates that the pathogen responsible for okra mosaic disease (OkMV), Tymovirus abelmoschi (Tymovirales: Tymoviridae), is the only virus causing significant losses in okra production that does not belong to the Begomovirus genus. Despite this distinction, co-infection with members of the Begomovirus genus is frequently reported [375]. OkMV disease can lead to yield losses of up to 90.0% [387]. Unlike begomoviruses, T. abelmoschi is transmitted mechanically by flea beetles Podagrica spp. and Nisotra spp. These insects are predominantly important for short-distance transmission [388,389].

The characteristic symptoms of OkMV include yellowish mottling of the plants, stunting, reduced yield, smaller leaves, and fruit abnormalities such as discoloration, distortion, and abortion [375].

6.4. Management Strategies

6.4.1. Host Plant Resistance

The cultivation of virus-resistant okra varieties is widely regarded as the most economical and environmentally friendly method for managing okra viral diseases. Specifically, varieties resistant to YVMV are already available, with new sources of resistance continuously being reported [390,391]. However, due to the high genetic variability inherent in begomoviruses, it is crucial to maintain ongoing screening efforts to identify additional sources of resistance [382,392].

In addition to resistance against YVMV, sources of resistance to OELCV disease have been discovered in various wild Abelmoschus species, such as A. crinitus, A. ficulneus, A. angulosus, and A. manihot [393]. Furthermore, Jamir, Mandal, et al. [28] identified a single genotype, BCO-1, which exhibits resistance to both YVMV and OELCV, highlighting the potential for breeding multi-disease-resistant cultivars. Moreover, a comparative study by Sergius and Esther [375] on the sensitivity of West African and conventional okra cultivars to leaf curl and okra mosaic infections revealed significant differences. West African cultivars, belonging to the species A. caillei, demonstrated moderate to high tolerance to both viruses, whereas conventional cultivars (A. esculentus) were moderately to extremely sensitive.

These findings emphasize the critical importance of continued efforts in developing and utilizing resistant varieties, particularly in light of the diverse viral threats faced by okra crops. Effective control of B. tabaci and Chrysomelidae species feeding on okra is crucial, as discussed in Section 3.4.

6.4.2. Cultural Control

Isolating okra fields from infection sources and managing alternative host plants in the vicinity are vital strategies [29]. Given that OkMV can be transmitted mechanically, disinfecting tools and promptly removing infected plants from the field are essential practices. Although seed transmission of the listed viruses remains uncertain, using seeds from healthy plants can enhance plant vigor and, when combined with optimal growing conditions, may reduce susceptibility to infection [394].

7. Bacterial Diseases of Okra and Their Management Strategies

Bacterial leaf spot and blight of okra have been reported worldwide, particularly from the 1960s to the 1980s [395,396,397]. The causal pathogens were identified as Pseudomonas syringae van Hall (Pseudomonadales: Pseudomonadaceae), although they were not assigned to any specific pathovars. Infected plants exhibited small, deformed, and brown-colored seeds compared with healthy ones [396,397]. Another phytopathogenic bacterium associated with these symptoms was noted, although specific identification details were not provided in the earlier reports.

Pseudomonas syringae pv. syringae van Hall is one of the most widespread and extensively studied plant pathogenic bacteria, known for its broad host range that includes both monocotyledonous and dicotyledonous plants. Its ability to infect okra was first documented in 1991 by Young [30]. In the same year, Brown and McCarter [398] reported an outbreak of P. syringae in greenhouses in Georgia, USA, affecting the medicinal plant Abelmoschus moschatus. Among 101 strains of P. syringae pv. syringae compared using repetitive PCR with the BOX primer, a strain isolated from A. esculentus in Kenya was found to be most similar to strains originating from Magnolia grandiflora and Citrus sinensis [399]. However, this same strain from Kenya grouped with 34 other P. syringae strains from diverse host plants and locations during a genome analysis of 102 P. syringae strains from various pathovars [400].

The pathogen has a low optimal temperature of approximately 19 °C and thrives in high humidity conditions [30]. Early symptoms of infection include angular, water-soaked spots on the leaves, which later develop into necrotic lesions. Elongated dark lesions on the stems and petioles have also been observed [398]. Additionally, seeds from infected plants were found to be small, deformed, and brown-colored compared with those from healthy plants [396,397].

Xanthomonas campestris pv. esculenti (Rangaswami & Easwaran) Dye (Lysobacterales: Lysobacteraceae) is associated with Pseudomonas syringae infections on okra [396,397]. The simultaneous infection by these pathogens leads to more severe symptoms. Studies by Addy [401] and Phookan and Addy [402] reported the formation of extracellular polysaccharides on infected okra plants, and a hypersensitive reaction as part of the plant’s defense response.

In a separate study, Jain et al. [403] isolated various fungi and bacteria from stored okra fruits. They identified five bacterial species: Actinomycetes sp., Pectobacterium (Erwinia) carotovora, Xanthomonas campestris pv. campestris, X. campestris pv. malvacearum, and P. syringae pv. syringae. Although the deterioration of the fruits was primarily attributed to the isolated fungi, the presence of these bacteria suggests that potentially pathogenic bacteria are also present on okra seeds.

7.1. Management Strategies

Since bacterial diseases of okra are considered minor, there are few sources mentioning possibilities for their control.

7.1.1. Host Plant Resistance

Breeding resistant cultivars is a promising and environmentally sound approach, as there are many examples of plant resistance to P. syringae and X. campestris in plants closely related to okra [404]. Induced resistance has proven to be an effective tool for controlling bacterial plant diseases [405], and it has already been successfully applied against pathogens such as Erwinia amylovora [406].

7.1.2. Cultural Control

Infected or contaminated seeds can be sources of infection; therefore, using healthy seeds and practicing seed dressing are important. For the same reason, crop rotation is essential to get rid of infested plant residues [394].

7.1.3. Mechanical Control

Infested plant residues serve as major reservoirs for bacterial pathogens, so these should be plowed deep into the soil or removed from the field [394].

7.1.4. Chemical Control

Chemical control of bacterial diseases in okra can be achieved through the use of copper fungicides or antibiotics such as streptomycin [394]. However, the use of copper fungicides is strictly regulated in the European Union, and the application of antibiotics as plant protection agents is prohibited.

7.1.5. Microbial Control

The control of pathogenic bacteria using antagonistic organisms is a well-researched and frequently implemented method. Various products derived from these antagonists are commercially available and can be applied to plants, soil, or seeds [407].

8. Integrated Management of Okra Pests and Diseases: Perspectives and Gaps

IPM is defined by the European Union Framework Directive on the Sustainable Use of Pesticides (Directive 2009/128/EC) as a careful consideration of all available plant protection methods and subsequent integration of appropriate measures that discourage the development of populations of harmful organisms and keep the use of plant protection products and other forms of intervention to levels that are economically and ecologically justified and reduce or minimize risks to human health and the environment. IPM emphasizes the growth of a healthy crop with the least possible disruption to agro-ecosystems and encourages natural pest control mechanisms [408]. The Food and Agriculture Organization of the United Nations [409] defined IPM as careful consideration of all available pest control techniques and subsequent integration of appropriate measures that discourage the development of pest populations. It combines biological, chemical, physical, and crop-specific (cultural) management strategies and practices to grow healthy crops and minimize the use of pesticides, reducing or minimizing risks posed by pesticides to human health and the environment for sustainable pest management.

In the context of okra, pest management has achieved notable advancements in certain areas, yet continues to encounter challenges in the comprehensive implementation of the eight principles of IPM as elaborated by the European Union [408]. Okra cultivation utilizes resistant varieties and crop rotation to avoid the risk of pest resistance even among genetically resistant crop varieties. Some studies have identified resistant okra varieties. For instance, the okra cultivar ‘SabzPari’ demonstrates resistance to multiple pests, including cotton spotted bollworm, Egyptian bollworm, cotton leafhopper, and root-knot nematodes, highlighting its versatility in pest management [108,163,213]. Similarly, ‘Arka Anamika’ shows resistance to cotton bollworm and moderate resistance to root-knot nematodes, making it a promising choice for integrated pest management strategies [175,216]. In the case of diseases, the genotype ‘BCO-1’ offers resistance to both YVMV and OELCV, two major viral threats in okra cultivation [28]. Furthermore, the cultivar ‘Santa Cruz-47’ has been identified as a promising source of resistance to Fusarium wilt, while the genotypes ‘AOL-15-23’ and ‘AOL-15-21’ exhibit resistance to collar rot, caused by M. phaseolina [344,357]. However, the availability of these cultivars is not confirmed. More importantly, their resistance does not cover all pests and diseases which threaten the crop, necessitating further research to enhance their effectiveness. The genetic resistance of okra to various pests and pathogens remains limited compared with other major crops, presenting a significant constraint on its sustainable production. Although resistant varieties such ‘SabzPari’ and ‘Arka Anamika’ have been developed, their distribution is insufficient, particularly in rural areas of developing countries where okra is predominantly cultivated [410,411,412]. This underscores the urgent need for expanding breeding programs focused on developing varieties with enhanced resistance traits and establishing efficient distribution networks to ensure that these varieties are accessible to smallholder farmers. Furthermore, the notion that full resistance is unattainable underscores the necessity of integrating genetic resistance with continuous monitoring of emerging virulent biotypes and pathogens possessing resistance-breaking genes [413]. Proper monitoring, which is crucial for the timely detection of pest and disease outbreaks, needs to be consistently implemented in okra cultivation, to avoid delays in response and take proactive action.

Combining pest-resistant varieties with biological controls such as the application of entomopathogenic fungi Beauveria bassiana and Lecanicillium lecanii is effective in reducing the impact of main pests such as the cotton aphid, whitefly, and cotton spotted bollworm, leading to increased okra yields [414]. This integration of biological methods with pest-resistant varieties offers a promising pathway for sustainable okra cultivation.

There is an increasing emphasis on biological controls and other non-chemical interventions, and also shifting towards more selective and environmentally friendly pesticides, which emphasizes the need for minimal and judicious chemical interventions only when necessary. The adoption of biological controls, such as egg parasitoids like Trichogramma sp., offers a viable IPM strategy for okra; however, its implementation is often hindered by the lack of access to these biocontrol agents and inadequate technical knowledge among farmers, particularly those operating small-scale farms. Unlike larger, commercial crops, okra lacks the infrastructure and extension support required to effectively integrate biological controls into pest management programs, highlighting the need for targeted educational initiatives and improved access to these agents within okra-growing regions [415].

A study comparing IPM strategies, bio-intensive management—focused on biological controls with minimal chemical use—and conventional chemical methods in okra cultivation shows that IPM, which incorporated seed treatments, traps, and selective chemical interventions, provided the most effective pest control and the highest economic returns for okra [414]. IPM resulted in the lowest fruit infestation rates and the highest crop yields compared to other management methods. Moreover, IPM approaches preserved populations of natural enemies such as spiders and ladybugs (coccinellids), which are essential for maintaining ecological balance in okra fields [414]. However, the increasing impact of climate change on pest and disease dynamics further complicates pest control in okra, emphasizing the need for adaptable IPM strategies. Climate change is exerting a substantial influence on pest and disease dynamics in okra cultivation, with rising temperatures, fluctuating humidity levels, altered precipitation patterns, and elevated atmospheric CO₂ creating conditions that enhance pest proliferation of key okra pests. Notably, the cotton spotted bollworm demonstrates significant temperature sensitivity, with warmer climates supporting more rapid life cycle progression and population growth, resulting in potential yield reductions of up to 70.0% under severe infestations [416,417]. High humidity, often resulting from erratic rainfall patterns, also promotes the growth of sucking pest populations, including cotton aphids and whiteflies, which thrive in moist conditions and contribute to increased resistance challenges [418,419]. Additionally, climatic changes influence pathogen dynamics, with fungal diseases like powdery mildew and Cercospora leaf spot becoming increasingly prevalent in warm, humid environments. Elevated CO₂ levels have been shown to accelerate pathogen growth rates, increasing disease severity and reducing crop quality [418]. These fungal pathogens, which thrive in high-humidity settings, complicate disease management by contributing to quality decline under intensified climate stress. These challenges reveal the limitations of conventional pest management approaches and underscore the need for climate-adaptive IPM strategies.

Socio-economic factors also impede the adoption of IPM in okra cultivation. Smallholder farmers often face significant resource limitations, including insufficient training, weak extension services, and inadequate financial incentives to adopt reduced pesticide use. These socio-economic barriers contribute to the persistent reliance on conventional chemical pesticides, which, although providing immediate pest control, undermine the long-term sustainability of okra farming systems. Despite these barriers, Mohapatra, Padhi, et al. [414] indicate that in okra cultivation, the adoption of IPM delivers the highest net return and incremental cost–benefit ratio compared to other pest management strategies. Addressing these challenges requires targeted policy interventions, including the provision of training programs, financial support, and incentives specifically tailored to the needs of okra farmers [411].

Additionally, stringent pesticide residue limits imposed by international markets, particularly in the European Union, present major challenges for okra exports. The prevalent use of chemical pesticides in okra not only restricts market access but also poses significant environmental and health concerns. To mitigate these issues, there is a critical need to prioritize IPM strategies that minimize chemical inputs, emphasizing cultural and biological controls that enhance compliance with global market standards while maintaining the economic viability of okra production. Furthermore, the dynamic nature of pest resistance underscores the need for rotating pesticide modes of action and integrating non-chemical methods to manage resistance and ensure effective pest management [415].

Okra cultivation offers opportunities for cost-effective cultural controls suited to smallholder farmers. Intercropping with barrier crops such as maize or sorghum and using yellow sticky traps are practical, low-cost strategies that reduce dependence on chemical pesticides. These methods align with okra’s agro-ecological conditions and the financial constraints of its growers, making them valuable elements of an integrated IPM approach [412].

Regular evaluations are essential to assess the effectiveness of pest management strategies, ensuring that IPM methods remain effective over time and allowing for necessary adjustments.

9. Conclusions

The high vulnerability of okra to numerous arthropod pests, nematodes, and fungal, viral, and bacterial pathogens necessitates the adoption of effective management practices. While chemical control provides rapid results with immediate control, its environmental impact and the risk of pesticide resistance highlight the need for alternative strategies. Combining pesticides with different modes of action decreases the risk towards environmental health and pesticide resistance. Biological controls, such as the use of natural enemies and antagonists, plant extracts, and other natural components, offer sustainable solutions. Cultural practices, including intercropping, rotations, and physical interventions such as traps, have also proven effective and are well-established in agricultural use. Screening for resistant okra varieties offers long-term management of and reduction in pest and disease impact. The integration of these methods within an IPM framework suggests a balanced, sustainable approach that could significantly diminish the effects of pests and diseases on okra. However, resistant okra varieties are limited and insufficiently distributed, especially in developing regions where they are most needed, highlighting the need for expanded breeding programs and improved access.

IPM principles emphasize the combination of various control strategies, including prevention and suppression, monitoring, decision-making, non-chemical methods, pesticide selection, reduced pesticide use, anti-resistance strategies, and regular evaluations. By adhering to these principles, within the framework of the constraints discussed previously, okra cultivation can achieve more sustainable and effective pest management, ultimately enhancing crop productivity and environmental health.

This review not only contributes to the current existing knowledge by synthesizing up-to-date research but also highlights the critical need for continued research into innovative, effective, and sustainable management strategies. This is particularly essential for less common pests and pathogens that are not extensively studied in okra, with the ultimate goal of enhancing long-term okra productivity. However, the adoption of biological controls is often limited by inadequate access to biological control agents and insufficient farmer education. Strengthening extension services and providing targeted training is critical to integrating these sustainable practices more effectively into okra farming systems. Socio-economic constraints, including limited training, weak extension services, and financial constraints, particularly affect smallholder farmers in developing countries, leading to a continued reliance on conventional pesticides. Addressing these challenges through targeted policies, training programs, and financial support is essential to promote the adoption of sustainable IPM practices.

Moreover, the continuous harvesting pattern of okra, where pods are frequently picked, increases the likelihood of pesticide residues remaining on the crop, making it particularly vulnerable to failing residue compliance tests. Reducing chemical inputs through IPM strategies that emphasize non-chemical methods, such as cultural and biological controls, can improve compliance with international standards and enhance market access.