Traditional Strategies and Cutting-Edge Technologies Used for Plant Disease Management: A Comprehensive Overview

Abstract

Agriculture plays a fundamental role in ensuring global food security, yet plant diseases remain a significant threat to crop production. Traditional methods to manage plant diseases have been extensively used, but they face significant drawbacks, such as environmental pollution, health risks and pathogen resistance. Similarly, biopesticides are eco-friendly, but are limited by their specificity and stability issues. This has led to the exploration of novel biotechnological approaches, such as the development of synthetic proteins, which aim to mitigate these drawbacks by offering more targeted and sustainable solutions. Similarly, recent advances in genome editing techniques—such as meganucleases (MegNs), zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs) and clustered regularly interspaced short palindromic repeats (CRISPR)—are precise approaches in disease management, but are limited by technical challenges and regulatory concerns. In this realm, nanotechnology has emerged as a promising frontier that offers novel solutions for plant disease management. This review examines the role of nanoparticles (NPs), including organic NPs, inorganic NPs, polymeric NPs and carbon NPs, in enhancing disease resistance and improving pesticide delivery, and gives an overview of the current state of nanotechnology in managing plant diseases, including its advantages, practical applications and obstacles that must be overcome to fully harness its potential. By understanding these aspects, we can better appreciate the transformative impact of nanotechnology on modern agriculture and can develop sustainable and effective strategies to mitigate plant diseases, ensuring enhanced agricultural productivity.

1. Introduction

Agriculture is the backbone of developing countries as 60% of the total population relies on it for their income [1]. In contrast to underdeveloped countries, it is an unpopular source of income in developed countries. Nowadays, it is a big challenge to fulfill the demand for food for the growing population. As predicted by the United Nations, the expected global population will be around 10 billion by 2050. This growth in population demands a 60% increase in food production to ensure a balanced food supply [2]. Therefore, researchers and scientists have worked on the issues of global food security to improve the production of agricultural products, including both crops and livestock. However, many factors—including high input expenses, drought, cross bordering of plant and animal pests and diseases, decline in soil organic matter, less land for farming, poverty, urban development, high competition of water and land, changes in regulatory landscapes, degradation of natural resources, diminished ecosystems, climate change and loss of biodiversity—affect the issue. An ongoing challenge for farmers is the incorporation of available technology to make conventional production systems more cost-effective [1,3,4,5,6]. Moreover, the contribution of animal pests to overall crop losses is 18%; microbial pathogens and weeds contribute approximately 16% and 34%, respectively. In microbial pathogens, nearly 70–80% of these crop losses are due to fungal pathogens [7]. A review of plant disease control methods is shown in Figure 1.

1.1. Conventional Agricultural Practices

Various conventional agricultural practices have been used for disease management, including field sanitation, legal methods, resistant varieties, cropping systems, soil solarization, bio fumigants, soil amendments, anaerobic soil disinfection, soil steam sterilization, soilless culture and soil fertility. Field sanitation is used to avoid pathogen spread in crop growing areas by managing humidity in the crop canopy, ensuring that it is not excessive, as most plant pathogens benefit from high humidity. Additional measures include the decontamination of equipment using heat treatment, (UV) treatment, and light treatment, as well as removing volunteer plants (such as weeds), ploughing the soil, and implementing appropriate tillage practices. These strategies help to minimize the conditions favorable to pathogen growth and reduce the risk of disease spread [8]. Additionally, legal measures have been adopted to avoid the spread of disease from infected areas to uninfected areas. Long-distance pathogen emerge in previously uninfected areas by means of plant propagation materials, packaging materials, containers and seeds [9]. It has been reported that the trading of ornamental plants was the main cause of phytophthora (P. palmivora and P. syringae, P. ramorum, P. drechsleri and P. nicotianae) in North America and Europe [10,11]. Lab testing and quarantine practices were adopted to avoid such disease incidences [9]. Moreover, the development of resistant plant varieties has also been an efficient approach used to manage plant diseases [12]. Nevertheless, genetic resistance loses its effectiveness over time because of the pressure of selection against phytopathogens, the emergence of new strains of plant pathogens that overcome that resistance or the interaction nematodes and fungi. However, soil-borne pathogens of the tomato plant, such as F. oxysporum f. sp. radicis-lycopersici and F. oxysporum f. sp. lycopersici, have been successfully controlled by using this method [13]. Multiple cropping systems—i.e., mixed cropping (the use of multiple lines in cereals), intercropping and crop rotation—were adopted to prevent pathogen inoculum, as growing the same crop in the same field year after year provides a host crop for pathogens and increases the risk of disease epidemics. In this manner, crop rotation is used to control disease, increase soil fertility and soil moisture and improve the physiochemical properties of soil [10]. Crop rotation involving barley and clover has been used to reduce Rhizoctonia canker and black scurf disease [14]. In addition, solar energy is another method for reducing soil pathogens. It involves spreading a plastic sheet on production beds just after irrigation. Solar radiation is trapped at the soil surface and heats the upper layer [13,15]. Deep tillage and exposure of the soil to solar radiation are recommended during the warmer months of the year to reduce the inoculum of soil-inhabiting plant pathogens. It is an effective approach in killing many important soil-borne pathogens, such as Sclerotinia spp., Fusarium spp., Agrobacterium tumefaciens, nematodes and Streptomyces scabies.

In addition to the above, Brassicaceae crops, such as canola, cabbage and rapeseed, have substances that can control soil-borne pathogens and pests. These crops have the ability to produce glucosinolates, which are sulfur compounds toxic to soil organisms such as P. nicotianae and R. solani, as well as to some nematodes species, such as Meloidogyne; these glucosinolates also act as biofumigants [16,17,18]. It is reported by Baysal-Gurel et al. that R. solani and P. nicotianae can be effectively controlled in woody ornamental plants by using cover crops [19]. In addition to this, soil steam sterilization is another approach that has been used in open fields or in greenhouses to sterilize the soil, ultimately inhibiting soil-borne diseases. Hot water vapors are injected into the soil using conductors and boilers; this technology is applicable for the disinfection of substrates and feedstocks in plant nurseries and greenhouses. It is a better way to control fungal pathogens than using methyl bromide or chloropicrin [20]. Although some biocidal products are effective, they damage the ozone layer and are banned in some countries. These products have more effectively controlled root knot nematode in Florida than treatment with methyl bromide [21]. The use of organic amendment is another conventional way of suppressing the growth of pathogens. Liquids and composts nourished with essential oils, organic acids, phenols and other biological compounds from herbs have also been used occasionally in managing plant diseases [22,23]. Today, the use of plant-based pesticides or phytoplaxicides has become very important for the environment and the safety of food. Organic manures, such as compost and peat moss, control soil-borne pathogens, such as Thielaviopsis basicola, Pythium, Sclerotium, R. solani, Fusarium and Phytophthora [24,25]. Along with improving soil health, organic amendments—which improve the physical properties of the soil and promote the growth of rhizogenic microorganisms—also enhance the activity of beneficial microorganisms in the soil, such as Pseudomonas, Rhizobacteria and Trichoderma. They enhance the production of plant growth regulators, phenols and tannins that have an antagonistic effect on disease-causing microbes [26].

Limitations of Conventional Agricultural Practices

These methods are effective in reducing the incidence of disease, but have a few limitations, as shown in Figure 2. These methods are ineffective on pathogens that have a broad range of host crops, and are effective in controlling only soil-borne pathogens (Rhizoctonia, Sclerotium, Fusarium, Macrophomina, etc.), which are characterized by having a wide range of hosts, normally between 200 and 500 crops [27]. They are also dependent on climatic conditions [15] and are time-consuming, fuel-consuming and laborious approaches, which make their adoption unappealing for controlling diseases [28]. Moreover, they are dependent on the physiochemical properties of the soil, the type of soil, the amount of organic amendments added, soil pH, cation exchange capacity and phytotoxicity [27]. In addition, the use of Brassica cover crops kills pathogenic microorganisms, but they also lead to increased phytotxicity and disease severity [29]. Due to their negative impacts, they are unable to support agriculture and yield production efficiently.

Seeing as there is a need to boost yields for a growing population, which will reach up to 10 billion by the end of 2050 [30], in order to address the concerns about food security, improving production is the ultimate goal, but one which cannot be achieved through conventional approaches. Global crop losses due to plant diseases are estimated to be about 16–20% of potential crop yields annually. Diseases such as wheat rust, rice blast and late blight in potatoes can cause up to 30–50% yield losses in severe cases. The economic impact of plant diseases is substantial. For example, wheat rust diseases alone have caused an estimated loss of USD 60 billion annually worldwide. The impact of fungal diseases on maize can lead to losses of up to UDS 1.5 billion per year in the U.S. alone. Therefore, to reduce pest pressure and to combat food security issues, agriculture has switched to chemical pesticides [31].

1.2. Chemical Pesticides

Chemical pesticides are target-specific and therefore have many subdivisions/classes, such as insecticides, bactericides, herbicides, nematicides and fungicides. Insecticides are used to kill insect pests, fungicides are meant to destroy fungal pathogens and herbicides are used to eradicate weeds, while bactericides are used to kill bacteria and nematicides are used to kill nematodes. Traditional synthetic pesticides are considered one of the most cost-friendly, effective and quick approaches for managing plant diseases [32,33]. They play a significant role in reducing crop losses caused by insect pests, microbes and weeds [34]. It has been reported that there was a 78% reduction in crop losses in fruit crops, 32% in cereals and 54% in vegetables due to the use of chemical pesticides [35]. As a result, a significant decrease in the hunger pattern has been observed since the mid-twentieth century. The prime objective of this pesticide use has been to improve crop production. However, apart from their profitable effects, they also hold many disadvantages [36]. The extensive use of fungicides, with their site-specific mode of action, can lead to the development of resistance in pathogens, environmental pollution, risks to human health and a decline in soil fertility by negatively impacting beneficial organisms, including predators, earthworms, and pollinators. Additionally, they can disrupt microbial diversity by altering soil conditions. However, it is possible to mitigate these effects through bioremediation, a process that involves introducing certain microbial organisms into the soil to help decontaminate and restore its natural balance. These beneficial microbes can break down harmful chemicals, improve soil health and support microbial diversity [32,33,36]. The activity of root colonizing microbes, such as bacteria, mycorrhizal fungi, Rhizogenous antagonist fungi and algae, is also affected in soil that is treated with exogenous pesticides, as these are toxic to the metabolic activity, growth and other factors of beneficial soil microbes [37]. The biochemical reactions of soil, such as nitrogen fixation, ammonification and nitrification, are also disrupted due to the activation or deactivation of specific microorganisms and enzymes [38]. Moreover, they cause retardation in soil organic mineralization, which is responsible for soil quality and its production capacity [39]. Along with their positive impacts, they also have negative impacts. For example, there is urea and ammonia present in pesticides that cause impairment of both environmental and human health. They cause metabolic issues—i.e., diabetes, infertility and endocrine disruptions, neurological disorders, compromised immune system and cancer—in humans [40,41]. Similarly, in recent years, synthetic and natural plant defense elicitors have emerged as promising alternatives or complementary strategies to chemical treatments. These elicitors, which activate plants’ innate immune responses, offer a more sustainable and targeted approach to disease control. For instance, synthetic elicitors like those described by the authors in [42] can mimic natural defense mechanisms, while novel proteins, such as those from Phytophthora parasitica [43], induce both basal immunity and systemic acquired resistance. Additionally, the intricate role of elicitor-receptor molecules in orchestrating plant defense, as discussed in [44], highlights the potential of these molecules in enhancing crop resilience to pathogens. In short, the continuous use of pesticides has had negative consequences on the environment and public health, and to some extent has contributed to a rise in disease incidence. The pros and cons of chemical pesticides are summarized in Figure 3. Therefore, as a sustainable alternative, biopesticides have become more and more popular due to their low toxicity and organic nature, and the fact that they are renewable, ecosystem-friendly and promote food safety [45].

1.3. Biopesticides

In order to reduce the increasing concerns related to chemical pesticide use, researchers have begun to utilize biopesticides [46], which involve the use of pesticides developed from living organisms (i.e., microorganisms and plants or synthesized substances derived from living organisms). Among these, botanicals or plant-based biopesticides have become more popular for the management of plant diseases without inducing toxicity to the food chain and are safer than agrochemicals, promoting safe food [47]. They are also non-toxic to the ecosystem and have an environment-friendly mode of action. The results of various studies have shown no related residual effects when applied in optimized concentrations [40]. Beneficial soil microorganisms are not harmed due to their target specificity [48]. Therefore, it is considered a sustainable pest management approach that has the ability to push agriculture towards sustainability [49]. The use of these natural pesticides is effective as they have not led to the development of resistance among pests [50]. Additionally, they have the ability to decontaminate soils through the addition of certain microbial organisms [51,52]. However, although biopesticides offer benefits, there are some obstacles that have prevented their implementation as an alternative in managing plant diseases. One of the major concerns is that high doses are required for their effectiveness under field conditions. The microorganisms (Trichoderma, Bacillus, Purpureocillium, etc.) used as biocontrol agents have the disadvantages of lack of adaptation and colonization. They should be applied preventively and repeatedly, and are not always available in commercial formulations. Plant-derived pesticides are dependent on the availability of their plant sources and their cultivation. Their formulations are difficult and should be applied at short intervals and at high doses; moreover, they have a shorter shelf life. The efficacy of microbial biopesticides is reduced by environmental factors such as temperature, UV light and desiccation. Moreover, they have issues of high costs and complexity in development [40]. In addition, many considerations are required before adopting biopesticides, including regarding the nature of the host and their ability to disperse [53]. This method has numerous resource constraints when it comes to its implementation [54]. Even today, biopesticides are generally unknown among policy makers, stakeholders and small-scale growers [55]. Due to all these limitations, this method has not been adequate for sustainable agriculture. Figure 4 offers a concise overview of the positive and negative aspects of biopesticides. Therefore, to revolutionize agricultural practices and to mitigate environmental concerns, a shift towards molecular techniques was imperative.

1.4. Molecular Techniques/Approaches

The integration of molecular techniques in crop improvement began in the latter half of the 20th century [56]. Numerous molecular techniques were used/adopted to achieve sustainable and targeted solutions for pest management, i.e., DNA barcoding and genome editing [57]. The mechanism of genome editing involves the use of sequence-specific nucleases (SSNs), which are programmable molecules that have the capacity to alter particular DNA sequences. It was reported that SSNs have been used to make targeted genome changes in multiple crops [58]. In genome editing, four principal mechanisms (meganucleases, zinc finger nucleases, transcription-like effector nucleases and clustered regularly interspaced short palindromic repeats associated protein 9 (Cas-9)) were used to perform targeted nuclease activities, which have opened the door to agricultural advancement [58].

1.4.1. Meganucleases (MegNs)

MegNs are naturally occurring endodeoxyribonucleases [59] that were discovered in the late 1980s. MegNs are members of the endonuclease family, which is capable of identifying and cleaving lengthy DNA sequences (between 20 and 40 base pairs) [60] found in a variety of microbial organisms, and can also be found in the mitochondria and chloroplast of eukaryotes [51]. In terms of molecular biology, the use of MegNs is adventitious due to their long recognition sites, high specificity, easy delivery, small size and their giving rise to more recombinant DNA by producing a 3′ overhang after DNA cleavage. In addition to this, they have the capacity to reduce the possibility of cytotoxicity [61,62]. Successful applications of MegNs have been seen in Arabidopsis, cotton and corn [63,64,65]. In an investigation, MegNs were developed to create resistance against insects and produce transgenic cotton by cleaving the specifically targeted DNA sequences [66]. It was reported that MegNs caused double strand breaks (DSBs) in embryogenic callus cells that lead to tolerance against two herbicides [67]. However, despite there being no reports on the use of MegNs in rice crops, it can potentially serve as an alternative option due to its low efficacy [63,64,65]. Additionally, the lack of naturally occurring MegNs is a major constraint, as it requires the costly, time-consuming and laborious construction of sequence specific enzymes [68]. Moreover, they can recognize a few specific DNA sequences, and there is a probability of errors due to deletion or addition at the cutting sites [63,69,70]. Figure 5 illustrates the key points of the capabilities and challenges of MegNs.

1.4.2. Zinc Finger Nucleases (ZFNs)

The era of ZFNs started in 1996, and they are recognized as site specific nucleases [71]. ZFNs are synthetic restriction enzymes that are capable of cleaving long stretches of double-stranded DNA sequences [72,73,74]. These are artificially engineered nucleases and the synthesis of their monomers involves the fusion of two domains: a Cys2-His2 zinc finger domain and a non-specific DNA cleavage domain from the DNA restriction enzyme Flavobacterium okeanokoites I (FokI) [75]. Despite their complex modular construction, ZFNs have been utilized intensively in the genetic modification of the Arabidopsis plant [73,74,76,77,78], tobacco (Nicotiana tabacum) [79,80], canola (Brassica napus), soybean (Glycine max) and maize (Zea mays) [75,81,82]. The abscisic acid (ABA) insensitive phenotype in Arabidopsis, herbicide resistance in tobacco and bialaphos resistance in maize were accomplished using ZFN technology [83,84,85]. Moreover, artificial zinc finger proteins (AZPs) have played a significant role in conferring antiviral resistance to plants by restricting the viral replication proteins’ DNA binding sites [86,87]. Chen et al. published a report employing ZFN technology to enhance disease resistance in crop plants. In this study, AZPs were designed to target a conserved sequence motif found in begomoviruses. Through this approach, the researchers achieved resistance against multiple begomoviruses—including Tobacco curly shoot virus (TbSCV) and Tomato yellow leaf curl China virus (TYLCCNV)—by specifically targeting a site within the viral DNA [88]. By preventing viral replication of the proteins’ DNA binding sites, artificial zinc finger proteins, or AZPs, have significantly increased plant resistance to viruses [86,87].

However, because of their engineering complexity and multiplexing difficulties, ZFNs have had a limited impact in inducing disease resistance in crops through the modification of genes that are associated with disease development [83,84,85]. Moreover, challenges such as off-target effects, low efficiency [89] and the existence of target sites that are sparsely distributed have made their use more challenging [90]. Figure 6 illustrates the benefits and drawbacks of ZFNs.

1.4.3. Transcription Activator-like Effector Nucleases (TALENs)

The limitations of ZFNs opened the door for a new class of nucleases: TALENs. Since the discovery of their DNA binding mechanism in 2009, it has become possible to use TALENs for DNA targeting [91,92], which are more efficient, safer and cheaper than ZFNs, and capable of targeting a specific site in the genome [93]. TALENs originate from phyto-pathogenic bacteria Xanthomonas spp. and their homologs from Ralstonia Solanacerum, and have a core DNA binding sites comprising tandem repeats made up of almost 30 to 35 identical amino acids [92,94,95]. Successful applications of this technology have been found in model plants, i.e., Arabidopsis and Brachypodium, and in some important cash crops, such as barley [96], maize [97,98] and rice. In rice, researchers successfully engineered resistance against bacterial blight disease in rice, caused by Xanthomonas oryzae, by changing the promoter region of the OsCWEET 14 gene, which is essential for susceptibility to the pathogen [99]. Similarly, targeting of the FAD2 gene has successfully improved the oil quality in soybean crops [100]. Wheat has acquired heritable resistance to powdery mildew disease after three homologs of MLO were successfully targeted for simultaneous knockout [101]. TALENs have been used to develop improved seeds that have a characteristic fragrance [102] and improved storage potential [103]. Additionally, TALENs-engineered potatoes have the characteristics suitable for cold storage and better processing qualities [104]. Despite the advancements and simplifications of TALEN methods, it remains complex for individuals unfamiliar with molecular biology studies. Moreover, compared to ZFNs, it faces certain constraints due to their larger size, which hinders delivery [105,106]. The construction of TALENs for genome editing via PCR is a difficult task due to the repetition of sequences required for their design. The requirement to create a new TALEN protein for every DNA target site increases the expense and time of their development. Since their cutting effectiveness is dependent on the target sequence, methylated DNA cannot be targeted using them [107]. A review of the pros and cons of TALENs is presented in Figure 7.

1.4.4. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)

The CRISPR/Cas9 system, sometimes referred to as “short regularly spaced repeats”, was discovered in the 1980s and is regarded as the third generation of genome editing tools (Figure 8). In 2013, it was utilized for modifications of a plants’ genome for the first time. In contrast to the earlier genome editing technology, i.e., ZNFs and TALENs, which relied on artificial proteins, CRISPR/Cas systems recognize DNA binding sites on the basis of DNA/RNA interactions [108]. The TALEN and ZFN tools, especially ZFNs, were overshadowed by the benefits of the CRISPR/Cas system due to their simple design for targeting any genomic sites, straightforward prediction of off-target sites and the potential to modify multiple genomic sites simultaneously [109,110,111]. The utilization of CRISPR for targeted mutation in the genome of the tomato has successfully induced resistance against bacterial speck disease caused by Pseudomonas syringae pv tomato [112]. Similarly, in the case of citrus canker caused by Xanthomonas citri ssp. citri, the LATERAL ORGAN BOUNDARIES 1 (CsLOB1) that promotes the proliferation of bacterium has been identified and successfully knocked out [113]. In another investigation, the connection between CsLOB1 and the effector PthA4 of the bacterium was disrupted by using CAS9 to develop immunity in plants against the bacterium Xcc [114]. Furthermore, it was reported that the apple and many other ornamental and commercially-important plants were seriously threatened by Erwinia amylovora. To reduce the impact of this bacterium, directly purified CRISPR ribonucleoprotein was injected into the protoplast of the apple by targeting three genes (DIPM-2, DIPM-1 and DIPM-4), and researchers observed enhanced resistance against apple fire blight disease [115]. Moreover, CRISPR technology was used to induce resistance against bacterial blight disease caused by Xanthomonas oryzae pv. Oryzae via modifications in the Xa13/cdc region [112]. Similar effects were achieved in the following cases: in the MLO-7/cds region against powdery mildew of grapes caused by Erysiphe necator [115], in the OsERF922/cds region against rice blast caused by Magnaporthe oryzae [116] and in the SlMlo1/cds region against powdery mildew of tomato caused by Oidium neolycopersici [117]. Barley plants resistant to wheat dwarf virus have been successfully developed using CRISPR/Cas9 mutagenesis [118]. CRISPR has not only induced resistance in plants, but has also improved numerous other features, such as crop production [119,120], quality of grain [121,122], resistance to biotic stress [70] and abiotic stress [123] and male sterility via simple [124] and multiplex genome editing [125,126]. Yet, there are some significant constraints that prevent the Cas9 system from being beneficial in the development of disease resistance. Firstly, the direct targeting of the S gene (pathogens exploit S genes to facilitate infection and disease progression) may result in some adaptive costs due to their linkage with other desirable genes. Furthermore, any mutations in the S gene may cause a disruption in its pathways that ultimately damages a large number of other products by causing mutations in the targeted gene. These mutations have the potential to cause phenotypic abnormalities (such as chlorosis, necrosis, leaf deformation, yellowing, etc.) and the shortage of important micronutrients (Fe, Zn, Mn, etc.) [127]. In short, the CAS system is susceptible to off-target mutations [128]. The efficacy of genome editing using CRISPR is directly affected by both the sequence and the location of the target [129,130], as well as by the method of transformation (stable or transient expression methods) [131,132,133]. Moreover, it has caused difficulties/issues for the virologists while trying to control the spread of plant DNA viruses. There is a chance for endogenous genes to be inactivated through mutations or recombination, and the variations in plant virus systems due to genome editing lead to the evolution of viruses resulting from the lack of proofreading mechanisms in RNA replication. When two or more strains of an RNA virus infect the same host plant, recombination can occur, leading to the formation of new viral strains with mixed genetic material [134,135]. Although genetically modified plants developed through this technology have low viral infection rates and remain stable for up to three generations, they are subjected to regulations for genetically modified organisms and may not be accepted in some countries [136]. Figure 6 illustrates the benefits and drawbacks of CRISPR.

Therefore, the need of the hour is to develop such techniques that could increase crop production and protection with high efficacy, a lower dose and that could be environmentally friendly [137]. By keeping in view all the pros and cons of all the previously used practices and technologies (conventional approaches, chemical control, biocontrol, genome editing), researchers can continuously work to come up with emerging technologies that may have better a capacity/potential to overcome all such drawbacks.

2. Nanotechnology Used for Crop Protection

In recent years, nanotechnology has gained the attention of researchers for agricultural production [138]. “Nanotechnology” is the invention of Richard Feynman, who received the Nobel Prize in Physics in 1965. In 1959, during an American Physical Society meeting at Caltech, he introduced the idea of manipulating matter at the atomic level by presenting a paper titled “There’s Plenty of Room at the Bottom”. Nanotechnology represents the cutting edge of material sciences, comprising substances with unique properties in comparison to their larger macroscopic counterparts [139]. It is the use of tiny particles that are ranging from 1 to 100 nanometers in size, known as nanoparticles (NPs), that have a great potential to be used in medical fields, agriculture and industries due their extremely small size and large surface area [140]. For the identification of plant pathogens, it was introduced as a fourth resourceful tool for cellular and molecular biology [141].

Agriculture-based nanotechnology holds great potential for dealing with issues related to food security, including precise farming, waste management, nutrition management and disease control [142]. The earliest example of nanotechnology used in agriculture was reported in 2004 in animal breeding, crop growth and aquaculture [143,144]. In agriculture, NPs with larger specific surface areas function as unique agrochemical carriers that enable site-specific and controlled delivery of nutrients and chemicals [145], by improving their stability and solubility through nanoencapsulations [140]. Moreover, in the agro-environmental sector, numerous potential uses for this technology have been reported in protecting soil [146], improving stress tolerance in plants [147] and in the removal of contaminants [143]. The use of nanocapsules and nanodevices for disease detection and treatment is another emerging area of nanotechnology in agriculture. This includes the use of enzymatic biosensors for targeted sensing, quantum dots for fluorescent labeling to biologically recognize pathogens and in situ sensors for real-time monitoring [148,149,150]. Nanosensors serve as an effective means of identifying nutrient deficiencies, toxicity levels, animal and plant diseases and improving food quality [151]. By using this emerging technology, we can sort out farming issues effectively [152]. It has shown remarkable results for innovation in agriculture via the introduction of the newest and latest methods for disease detection, specified treatments, improved plant capacity for nutrients absorption, tackling disease and facing environmental challenges [141]. Furthermore, genetic modifications and seed treatments have been altered by agricultural nanotechnology. The coating of seeds with NPs promotes root development and early disease resistance and enhances seed germination [153]. Accurate genetic modifications have become possible through nanogenomics that optimize plants’ characteristics for increased adaptability, nutritional value and productivity [153]. In short, it can be concluded that nanotechnology holds the potential to push agriculture towards sustainability [154]. The NPs are classified as inorganic, organic, carbon based and polymeric.

2.1. Inorganic NPs

In the composition of inorganic NPs, carbon atoms are totally absent. These include metal-based and metal oxide-based NPs [155].

2.1.1. Metallic NPs Used for Plant Disease Management

The most common categories included in metal NPs are copper (Cu), cadmium (Cd), gold (Au), Aluminium (Al), Cobalt (Co), Zinc (Zn), Lead (Pb) and Silver (Ag) [156]. On the basis of their size and characteristics, they possess extraordinary properties, such as cylindrical and spherical shapes, amorphous and crystalline structures, small surface area, pore sizes and surface charge densities [157]. Moreover, their numerous remarkable properties have been elaborated on by researchers in the field of agriculture, including their prolonged storage durability, high efficacy, extremely small size and easy transportation and handling when used in an appropriate way. Consequently, these nanomaterials hold the potential to be superior to traditional agrochemicals and to be the preferred choice of farmers [158]. This review will present the overview of previous research focusing on the utilization of metallic nanoparticles (NPs) in crop protection. We summarize the findings and advancements in this field in

Table 1. Applications of metal NPs in plant disease management.

MNPs	Concentration	Source of Synthesis	Size of NPs (nm)	Disease & Pathogen Management	Reference
Au	200 ppm	Biosynthesis	N/A	Sheath blight of rice caused by Rhizoctonia solani	[159]
	2 ppm	Trichoderma atroviride	50–75	Phomopsis canker in tea pant	[160]
	0, 20, 40, 60, and 80 ppm	Bacillus sonorensis	10–35	Dematophora necatrix, Fusarium oxysporum, Alternaria aternata, Alternaria mali, Sclerotium rolfsii and Colletotrichum capsici	[161]
	150 ppm	Metarhizium anisopliae	9–54	Rice blast disease	[162]
Zn	50, 100, 250, and 500 ppm	N/A	DLS: 30–40 TEM: 15–20	Aspergillus niger	[163]
	0–65 mg/L	N/A	>50	Peronospora tabacina	[164]
Ag	25 ppm, 37.5 ppm and 50 ppm	N/A	3 to 10	Fusarium oxysporum f. sp. radicis-lycopersici	[165]
	2, 4 and 10 µg/mL	Serratia sp	10 to 20	Spot blotch of wheat (Bipolaris sorokiniana)	[166]
	17.24 μg/mL	Azadirachta indica	15	Bakanae of rice (F. fujikuroi and F. proliferatum)	[167]
	50 ppm	Azadirachta indica	N/A	Early blight of tomato (Alternaria solani)	[168]
	40 mg/L	Allium sativum bulb	N/A	Spot blotch of wheat (B. sorokiniana)	[169]
	40 ppm	Avena fatua	5 to 25	Fusarium oxysporum f. sp. lycopersici	[170]
	40 mg/L	Allium sativum bulb extract	N/A	Black leg and soft rot of potato	[169]
	7.8 μg/mL	Pseudomonas canadensis	21 and 52	Brown blotch of mushroom (Pseudomonas. tolaasii.)	[171]
	100 ppm	Pleurotus ostreatus	N/A	Fusarium oxysporum	[172]
	0.35 mg/100 uL	Hyppophae rhamnoides	N/A	Ralstonia solanacearum and Pseudomonas syringae	[173]
	N/A	Malva parviflora L.	50.6	Helminthosporium rostratum, Fusarium solani, Fusarium oxysporum, and Alternaria alternata.	[174]
	150 ppm	Penicillium verrucosum	10–12	F. chlamydosporum and Aspergillus flavus	[175]
	15 μg/mL	leaf extract of rice	16.5	Xanthomonas oryzae pv. oryzae	[176]
	20 μg mL	Bacillus sp.	22–41	Red rot of sugarcane (Colletotrichum falcatum)	[177]
	N/A	Pseudomonas poae	19.8–44.9,	Head blight of wheat (Fusarium graminearum)	[178]
Cu	20 ppm	CuSO4 precursor	35–70	Macrophomina phaseolina, Bipolaris maydis, and Fusarium verticillioides In maize	[179]
	50 ppm	CuSO4 precursor	35–70	Rhizoctonia solani in maize	[179]
	30 ppm	CuSO4 precursor	35–70	Erwinia carotovora and Ralstonia solanacearum in maize	[179]
	≥80 ppm	Chemical reduction of Cu2+ with reductive agent of NaHB4	26.5	Fusarium oxysporum	[180]
	500 ppm and 1000 ppm	Eucalyptus and Mint leaves	10–130 23–39	Colletotrichum capsici of chilli	[181]
	N/A	Pseudomonas fluorescens, Trichoderma atroviride and Streptomyces griseus	N/A	Red root-rot disease in tea (Poria hypolateritia), collar canker (Phomopsis theae)	[182]
	20 ppm 50 ppm 30 ppm	CuSO4 precursor	35–70	Macrophomina phaseolina, Bipolaris maydis, and Fusarium verticillioides. Rhizoctonia solani. Erwinia carotovora and Ralstonia solanacearum.	[179]
	100 µg/mL	Bacillus altitudinis strain WM-2/2	29.11–78.56	Bacterial fruit blotch (BLB) of watermelon (Acidovorax citrulli)	[183]
	N/A	Chemical synthesis	28	Bacterial leaf blight (BLB) of rice (Xanthomonas oryzae pv. Oryzae)	[184]
	100, 150 and 200 ppm	Chemical synthesis and green synthesis	126 and 85	Root knot nematode (Meloidogyne Incongita)	[185]

, highlighting their effectiveness in improving crop health by minimizing biotic and abiotic stress factors.

2.1.2. Metal Oxide NPs

Small metal oxide particles have unique characteristics because they are extremely small and their surface atoms can easily combine in reactions, making them different from bigger forms [186]. The most common varieties include Aluminum oxide (Al₂O₃), Cerium oxide (CeO₂), silver oxide (Ag₂O), copper oxide (CuO), Magnesium oxide (MgO), Iron oxide (Fe₂O₃), Magnetite (Fe₃O₄), Silicon dioxide (SiO₂), Titanium oxide (TiO₂) and Zinc oxide (ZnO) [187]. All of these MONPs possess remarkable properties, which include effective surface qualities, high thermal and chemical stability and flexibility in pore size. These outstanding properties have gained the attention of researchers and have caused them to be considered one of the superior agents for agricultural production. Multiple MONPs have been employed to understand their long-term impact in crop production and plant growth. The results have shown significant effects in absorption, accumulation and movement of the plant, leading to an overall improvement in agricultural output. Additionally, they are highly valuable in the prevention and control of plant diseases and pests due to their increased durability, efficacy and, in particular, their large surface area, which favors their interactions with living plant cells [188]. Furthermore, they are less toxic, highly stable [189], antifungal, antibacterial [190] and antioxidant [191]. A review of the results from numerous research findings that underscore the advantage of metal oxide NPs in crop protection is shown in

Table 2. Applications of metal oxide NPs in plant disease management.

MONPs	Concentration	Source of Synthesis	Size of NPs (nm)	Disease & Pathogen Management	Reference
ZnO	130.1 and 104.9 µg/mL	Carica papaya leaf extract	N/A	S. sclerotiorum	[192]
	10% of 3 mL/L	PVP/ZnSO4 irradiated to 30 kGy.	38	Black mould of pomegranate (Aspergillus niger)	[193]
	5% of 9 mL/L.	PVP/ZnSO4 irradiated to 30 kGy.	38	Green mould of orange (Penicillium digitatum)	[193]
	20 mg/L	Cinnamomum camphora	13.92, 15.19 and 21.13	Early blight of tomato (Alternaria solani)	[194]
	18.0 µg/mL	Matricaria chamomilla flower extract	8.9 to 32.6	Bacterial wilt of tomato (Ralstonia solanacearum)	[195]
	1.0 mg/mL	Trachyspermum ammi	48.52	Fruit rot (Rhizoctonia solani)	[196]
	100 ppm	Eucalyptus globules	52–70	Alteraria blotch (Alternaria mali), Botryosphaeria canker of apple (Botryosphaeria dothidea)	[197]
	250 ppm	N/A	N/A	Purple Blotch disease in onion (Alternaria porri)	[198]
	100 µg/mL	Picea smithiana extract	25	Bacterial leaf spot of tomato Bacterial wilt of tomato	[199]
	100 µg/mL	Trichoderma harzianum	25–60	Fusarium wilt of tomato (F. oxysporum)	[200]
	200 μg/mL	Cannabis sativa L.	13.51	Fusarium virguliforme in soybean	[201]
	100 mg/mL−1	lemon peels	16.8	Citrus black rot (Alternaria citri)	[202]
Ag2O	0.10 and 0.20 g/L	solid homogeneous solution of silver oxide material	38.23	Pseudomonas syringae pv. tomato, Xanthomonas campestris pv. vesicatoria, Pectobacterium carotovorum subsp. carotovorum, Ralstonia solanacearum, Fusarium oxysporum f. sp. lycopersici and Alternaria solani in tomato	[203]
CuO	N/A	Hibiscus rosa-sinensis L. flower extract	28.1	Xanthomonas oryzae pv. oryzae	[204]
	10 ppm	coffee powder	85–100	Fusarium wilt in chickpea	[205]
	200 μg/mL	Cannabis sativa L.	7.36	Fusarium virguliforme in soybean	[201]
	N/A	Chemical synthesis	25.54 and 25.83	Root rot disease in cucumber (Fusarium solani)	[206]
	10, 15, 30, 50, 70, 100, and 150 mg/L	Pseudomonas fluorescens and Trichoderma viride	40–100 and 20–80	Gummosis of citrus (Phytophthora parasitica)	[207]
	5–350 μg/mL	Cassia fistula	12–38	Fusarium wilt of tomato (Fusarium oxysporum f. sp. lycopersici)	[208]
	200 ppm	Trichoderma asperellum	22	Alternaria brassicae	[209]
	200.0 μg/mL	Hibiscus rosa-sinensis L.	28.1	Bacterial leaf blight of rice (Xanthomonas oryzae pv. Oryzae)	[204]
	200 ppm	Jatropha curcas	5 to 15	Root-knot nematode in chickpea (Meloidogyne incognita)	[210]
	100 mg/mL	lemon peels	18	Citrus black rot (Alternaria citri)	[202]
SiO2	100 mg/L	N/A	54–76	P. syringae	[211]
	50, 100, 150, 200 and 250 ppm	bioleaching of sand	22.5	Meloidogyne javanica	[36]
	2, 20, 200 and 2000 ppm.	Green synthesis	58.6	Vigna radiata L.	[212]
	200 µg/mL	Crocus sativus L.	N/A	Bacterial leaf blight of rice (Xanthomonas oryzae pv. Oryzae)	[213]
	250 to 1000 mg/kg	agro-waste	N/A	Fusarium oxysporum (Fusarium wilt in Eruca sativa)	[214]
	150 ppm	Green synthesis	N/A	Pepper bacterial leaf spot (Xanthomonas vesicatoria)	[215]
	25, 50, and 100 µg/mL	saffron extract	9.92 and 19.8	Rhizoctonia solani	[216]
	50 mg/L	Milled/acid leaching rice husk	15	Bakanae of rice (F. fujikuroi)	[217]
TiO2	100 and 200 mg/L	N/A	21	Pectobacterium betavasculorum, Rhizoctonia solani, and Meloidogyne incognita in beetroot	[218]
	40 mg/L	Moringa oleifera Lam	10–100	Spot blotch of wheat (Bipolaris sorokiniana)	[219]
	0.20 mg/mL	N/A	5–15	Phomopsis vexans, Ralstonia solanacearum, and root-knot nematode (Meloidogyne incognita) in egg plant	[220]
	50 µg/mL	mixing of TiO2 solution with a lemon fruit extract at room temperature	41.5	Soft rot of sweet potato (Dickeya dadantii)	[221]
	100 ppm	Aspergillus versicolor	47.15	Leaf blight of tomato (Alternaria alternata)	[222]
	25, 50 and 75 μL	Trianthema portulacastrum, Chenopodium quinoa and by chemical conventional (sol-gel) method	<15	Wheat rust (Ustillago tritici)	[223]
	40 mg/L	Moringa oleifera	<100	Stripe rust (Puccinia striiformis f. sp. tritici)	[224]
	150 µg/mL	Chemical (sol gel) synthesis	20	Tobacco mosaic virus in chili pepper	[225]
	400 mg/L	Green synthesis by African palm oil and Chemical synthesis by sol gel method	14.60 ± 0.44 and 12.30 ± 0.54	Fusarium solani	[226]
CeO2	50 and 250 mg/L	N/A	8 ± 1	Fusarium wilt (Fusarium oxysporum f. sp. lycopersici)	[227]
	30 mg/L	Acorus calamusas rhizomes	42	Wheat stripe rust (Puccinia striformis)	[228]
	100 mg/L	Chenopodium quinoa L.	7–10	Ustilago tritici in wheat	[229]
Fe2O3	20 µg/mL	Green synthesis by hydrothermal process	HRTEM: 5 ± 1.0 DLS: 7.5 XRD: 5.95	Fusarium wilt (F. oxysporum)	[230]
	1.0 mg/mL	Green synthesis	49	Fusarium fruit rot (Fusarium oxysporum)	[231]
	1.0 mg/mL	Trichoderma harzianum	17.78	brown rot of apple (Fusarium oxysporum)	[232]
	0, 10, 50, 250 and 500 6.2 μg/mL	Mentha spicata	21–26	E. coli and B. cereus	[233]
	6 mg/mL	Skimmia laureola leaf extract	56–350	Bacterial wilt (Ralstonia solanacearum)	[234]
	1.0 mg/mL	Azadirachta indica	24	brown rot of sweet oranges (Fusarium oxysporum)	[235]
	100 and 200 ppm	Thyme plant	N/A	Gray mold of strawberry (Botrytis cinerea)	[236]
	1.0 mg/mL	Calotropis procera	49	Fusarium fruit rot of loquat	[231]
	15, 10 and 5 mg/L	Dried Guava	29–41	Alternaria solani	[237]
	1.0 mg/mL	Calotropis procera	32	Fruit rot of cherry (Aspergillus flavus)	[238]
Al2O3	1, 6 and 50 mg/100 mL	Pepsi cans	4–10	A. flavus, Fusarium sp. and Alternaria sp.	[239]
	150 mg/mL	Colletotrichum sp.	39 ± 35	F. oxysporum	[240]
CoO	200 µg/mL	Hibiscus rosa sinensis flower	34.9	Bacterial leaf blight of rice (Xanthomonas oryzae pv. oryzae)	[241]
Fe3O4	0.01–15 μg/mL	Spinach	20	Fusarium Wilt of tomato (Fusarium oxysporum)	[242]
	10 µg/mL	Spinacia oleracea	4	Fusarium wilt of tomato	[208]
	1000–1400 ppm	N/A	50 ± 5	Onion white rot (Sclerotium cepivorum)	[243]
	10, 40 and 80 mg/L	Chemical co-precipitation synthesis	60 to 72	Acremonium Wilt of sorghum (Acremonium striticum)	[244]
MgO	100 μg/mL	Green synthesis	29–60	Rhizoctonia solani, Acidovorax oryzae	[245]
	4 μg/mL	Aqueous Rosemary extract	<20	Xanthomonas oryzae pv. oryzae	[246]
	16.0 μg/mL	Paenibacillus polymyxa	10.9	Xanthomonas oryzae oryzae	[247]
	75, 150, 300, and 500 μg/mL	Strawberry	100	Root-knot nematode (Meloidogynidae)	[233]
	3 mg/mL	Chemical synthesis	N/A	Brown rot of potato (R. solanacearum)	[248]
	50 and 100 mg/L	Lemon fruit extracts	N/A	Alternaria leaf blight of carrot	[249]
	20 mg/mL	Acinetobacter johnsonii strain RTN1	18 to 45	Acidovorax oryzae	[245]
	15.36 μg/mL	Burkholderia rinojensis	26.70	Fusarium oxysporum f. sp. lycopersici	[250]
	200 ppm	S. cerevisiae	27	Callosobruchus maculatus	[251]
	50 μg/mL	Green synthesis	N/A	Phytophthora infestans	[252]
	75, 150 and 200 mg/L	N/A	52.5 to 57.3	Black scurf of potato (Rhizoctonia solani)	[253]
	74.81, 82.94, and 91.19 mg/g	Magnesium nitrate hexahydrates precursor	52.97 ± 1.43	Powdery mildew of peppers (Oidiopsis sicula)	[254]
	500, 1500, 2500 mg/L	Magnesium nitrate hexahydrate precursor	21.8	Clubroot caused by Plasmodiophora brassica	[255]
	79.43 ppm	Alcoholic extract of the bark of the walnut tree	28.55	Thielaviopsis paradoxa and Thielaviopsis punctulata	[256]
	100, 200, and/or 1000 μg/mL	N/A	20	Bacterial spot of tomato (Xanthomonas perforans)	[257]

.

2.2. Organic NPs

Organic NPs are environment friendly and nontoxic, and are also known as nanocapsules. Organic NPs that have high sensitivity when exposed to light and heat are liposomes, dendrimers, ferritin and micelles [258]. They have potential in various fields due to their properties, such as high reactivity with target substances and susceptibility to many factors, including heat, moisture, the atmosphere and light. They have toxic properties, as well as antibacterial, antifungal and disinfection properties that increase their value in the biomedical field. Furthermore, they possess oxidation, reduction and anti-corrosion properties. They have elasticity, flexibility, ductility, tensile strength, hydrophobicity, settling tendencies, suspension behavior, and diffusion rate make the valuable in diverse fields. Moreover, they are conductors, semiconductors and resistant [187]. Numerous researchers have investigated the antimicrobial potential of organic NPs, and their findings are summarized in

Table 3. Applications of organic NPs in plant disease management.

Organic NPs	Concentration	Nanocomposite	Disease & Pathogen Management	Rerefernces
Micelles	0.013 to 0.042 mg/mL	Carboxymethylchitosan (CMCS) micelles	Smart delivery of agrochemicals	[259]
	N/A	Hexaconazole/dazomet-micelle	Bio-fungicidal activity against Ganoderma boninense	[260]
	30 mg/L	Linear Supramolecular Block Copolymer Micelles	Rhizoctonia solani	[261]
	10, 20, 40, and 80 μL/L	Humidity-Responsive Cinnamon Essential Oil Nano micelles	High antifungal activity against Botrytis cinerea and nano-vesicles for preservation of fruit or vegetable	[262]
Liposomes	10 µg/mL	Liposomes bounded amphotericin	F. oxysporum f. sp. ciceris in chickpea	[263]
	0, 1 and 3 g/L	Tea tree oil solid liposomes (TTO-SLPs)	Brown rot of peach fruit caused by Monilinia fructicola	[264]
	0.046 mg/L	Nano-Insecticide through Encapsulation of insecticides in Polymeric Liposomes	Fall armyworm Spodoptera frugiperda	[265]
	136.59 and 83.99 mg/L, 315.78 and 154.34 mg/L	Eleocharis dulcis peel extract (EDPE) nanoliposomes	Megoura crassicauda and Acyrthosiphon pisum	[266]

and

Table 4. Characteristics of Organic Nanoparticles in Disease Management.

Organic NPs	Concentration	Size (nm)	Disease & Pathogen Management	Reference
Dendrimers	24 μg	1.1, 1.8, and 3.2	Cotton bollworm cells and larvae (H. armigera)	[267]
	500, 1000, 2000 and 5000 ppm	20 to 30	Phytophthora infestans	[268]
Ferritin	N/A	N/A	Changes in the regulation of iron homeostasis are involved in increasing resistance to Common scab caused by Streptomyces scabies	[269]
	N/A	N/A	Enhanced resistance against fire blight of pear caused by Erwinia amylovora	[270]

.

2.3. Carbon-Based NPs

The most significant class of NPs is carbon-based nanomaterials (CB-NMs) [271], which include fullerenes, carbon nanotubes (CNTs), graphene, graphene oxide and carbon nanofibers (CNFs). They have been extensively utilized in waste water treatment, crop protection, agriculture, antimicrobial activities, sensor technology and medicine due to distinctive features. Their uniqueness stems from their large surface area as well as electrical and optical [272,273,274,275,276,277]. thermal, mechanical and chemical properties [271]. Furthermore, CB-NMs, particularly, graphene, CNFs and CNTs, exhibit strong penetration capabilities, which enable their easy penetration through the seed coat and movement throughout the plant from roots to leaves and shoots. They serve as carriers of metal, metal oxide and agrochemicals by facilitating their easy translocation within the plant. This translocation ability of CB-NMs is observed due to their negatively charged surfaces, as well as their size [278]. Carbon-based materials have been extensively used in crop protection in multiple studies. A review of those studies and their findings is shown in

Table 5. Properties of Nanoparticles in Disease and Pathogen Management.

	Concentration	Source	Size	Disease & Pathogen Management	Reference
Carbon nanotubes	100 mg/L	N/A	30–50 nm	Stem and fruit rot and leaf blight of tomato caused by Alternaria solani	[279]
	200 mg/L	N/A	20–30 nm	Powdery mildew of roses caused by Podosphaera pannosa	[280]
	19 and 23 mg/mL.	Pulsed laser ablation in liquid (PLAL)	23 nm	Fusarium oxysporum	[281]
	100, 200 and 500 mg/L	N/A	20–30 nm	Tobacco mosaic virus in Nicotiana benthamiana	[282]
	100 and 500 mg/L	Chemical synthesis	52 ± 1.2 nm	Stalk rot caused by Fusarium verticillioides in Maize	[283]
Fullerenes	100, 200 and 500 mg/L	N/A	50 nm	Tobacco mosaic virus in Nicotiana benthamiana	[282,284]
	100 mg/L	N/A	50 ± 5 nm	Cucurbit Chlorotic Yellows Virus (CCYV) Infecting Nicotiana benthamiana	[284]

,

Table 6. Properties of Nanocomposites in Disease and Pathogen Management.

	Concentration	Nanocomposite	Size	Disease & Pathogen Management	Reference
Graphene	150 μg/mL	Reduced graphene oxide/silver nanocomposite (rGO-Ag)	7–26 nm	Chocolate spot disease of broad bean caused by Botrytis fabae	[285]
	200 mg/L	Reduced graphene oxide copper oxide (rGO-CuO)	0.55 to 3.74 nm	Powdery mildew of roses caused by Podosphaera pannosa	[280]
	1 mg/L	Reduced Graphene Oxide Nanosheet-Decorated Copper Oxide (rGO-CuO)	5, 20 and 50 nm	Fusarium wilt and root rot	[286]
	50 and 500 µg/mL	Reduced graphene oxide based Cu and Ag NPs (rGO-Cu/Ag)	SEM: 2.4 nm EDS: 40 nm	Bacterial spot of tomato and pepper caused by Xanthomonas euvesicatoria	[287]
	1280 μg/mL	Bi2O3/TiO2@reduced graphene oxide (rGO)	N/A	Pseudomonas syringae tomato	[288]
	N/A	Graphene quantum dots (GQD)	2–5 nm	Fusariusm head blight of wheat caused by Fusarium graminearum	[289,290]
	50 and 250 μg/mL	Graphene oxide-Fe3O4 nanocomposites (GO- Fe3O4)	30–36nm	Downy mildew of grapevine (Plasmopara viticola)	[291]

and

Table 7. Impact of Nanoparticle Types on Crop Performance.

	NP Type	Crop	Effect	Reference
Carbon Black	Modified nanoscale carbon black (MCB)	Ryegrass and chard	Reduction of heavy metals, increased plant growth and enhanced microbial communities	[292]
Carbon nanofibers	Acylated homoserine-coated iron-carbon nanofibers	Chickpea	Suppression of Fusarium oxyssporum f. sp. ciceris	[292]
	Carbon nanofiber CNF-Cu	Chicory	Improved water absorption, germination rate, shoot and root ratio and protein content	[289]
	Acylated homoserine lactone coated-iron carbon nanofiber (AHL/Fe-CNF)	Cicer arietinum and Triticum aestivum	Fusarium wilt of chickpea and root rot of wheat caused by Fusarium oxysporum f. sp. ciceris and Cochliobolus sativus	[293]
	Carbon nanofibers (CNFs)	Maize and barley	Resistance against fungal diseases and enhanced seed germination	[294]

.

2.4. Polymeric NPs

Polymeric NPs play a substantial role as drug nanocarriers in plants, functioning either as pesticides or plant growth regulators [295]. Research conducted over the past decade has found that the most important polymeric NPs in the agricultural sector are alginate [296,297,298,299], chitosan [300,301] and zein [302,303,304]. Meanwhile, the realm of synthetic polymers PLGA (poly lactic-co-glycolic acid) has been crucial in developing new NP-based materials [295]. Researchers have focused on polymeric NPs due to their potential to control the release of active ingredients and to protect them from unfavorable environmental conditions. Their stability and ability to deliver the active ingredients more precisely and accurately to the targeted areas of plants have generated significant interest in their use within agriculture. Additionally, the biodegradable and biocompatible properties of polymeric NPs result in low ecological toxicity. Furthermore, the encapsulation of large numbers of active ingredients and their slow release minimizes the environmental impact. Therefore, they need to be combined with active compounds such as herbicides, pesticides and antibiotics [143]. Polymeric NPs in agriculture also enable the efficient delivery of drugs, enhanced adhesion in soil, uptake by plants, thermal and photostability and reduce soil leaching [305]. Their coatings as nanocarriers enhance the life span of drugs due to their outstanding properties, such as easy water dispersal and their bioavailability for hydrophobic compounds. Biodegradable and biocompatible polymers can be considered as an alternative to inorganic NPs in order to minimize the issues of ecological toxicity [295]. This review focuses on the applications of polymeric NPs in crop protection shown in Table 8, highlighting their efficacy in delivering and stabilizing active molecules.

In addition to conventional nanomaterials, recent developments in self-assembled nano-bioprotectants have shown great promise for sustainable crop protection. These nanomaterials, which can self-assemble into functional structures, offer precise delivery and the controlled release of active compounds, enhancing their efficacy and reducing their environmental impact. For instance, Ref. [306] demonstrated the high efficiency of a self-assembled, multicomponent nano-bioprotectant in managing potato late blight. Similarly, Ref. [307] reported the successful use of self-assembled nanoparticles of a prodrug conjugate based on pyrimethanil for efficient disease control. Furthermore, Ref. [308] developed a plant protein-based self-assembling core-shell nanocarrier that not only controls plant viruses effectively but also promotes plant growth and induces resistance. These advancements highlight the potential of self-assembled nanomaterials in enhancing crop protection while addressing sustainability concerns.

Nanoparticles have been increasingly utilized to improve the efficiency of both traditional and frontier plant disease control strategies. Their unique properties allow for better delivery, stability, and controlled release of agrochemicals, contributing to enhanced disease resistance. For example, the authors of [309] discuss the role of nanoparticle-mediated strategies in enhancing plant disease resistance, illustrating their ability to work synergistically with traditional methods. Additionally, advanced applications, such as the use of exosome/liposome-like nanoparticles as carriers for CRISPR-based genome editing in plants, represent a frontier strategy in disease control [310]. These nanoparticles improve the precision and effectiveness of gene editing technologies, opening new avenues for crop improvement and disease management.

Table 8. Applications of carbon NPs in plant disease management.

Polymeric NPs	NPs Type	Concentration	Disease & Pathogen Management	References
Chitosan	Moringa chitosan NPs	200 mg/L	Rice blast (Magnoparthae oryzae)	[311]
	Chitosan in acetic acid distilled water solution	4 g/L	Dry rot and wilt (Fusarium sp.)	[312]
	Chitosan biopolymer	2.5 mg/mL	Powdery mildew of cucumber	[313,314]
	Chitosan	100 and 200 µg/mL	Bacterial wilt of potato and tomato	[315]
	Bioengineered chitosan iron nanocomposites	In vitro: 250 μg m/L In vivo: 250 μg m/L	Bacterial leaf blight of rice (Xanthomonas oryzae pv. oryzae)	[172]
	Chitosan	300 mg/L and 400 mg/L	Bean yellow mosaic virus of faba bean	[316]
	Chitosan composite film having chitosan, calcium, auxiliaries, ferulic acid and dextrin	0.71–1.42 g/L	Soft rot of kiwi (B. dothidea and Phomopsis sp.)	[317]
	Copper chitosan NPs	0.10, 0.20, and 0.30 mg/mL	Fusarium wilt of banana (Fusarium oxysporum f. sp. cubense)	[318]
	Chitosan	0.1–2.0 g/L	Root rot of fenugreek (Fusarium solani)	[319]
	Chitosan	500 mg/L	Powdery mildew of Rosa roxburghii	[320]
	Chitosan	0.2 g/L and 0.4 g/L	Blue mold of apple (Penicillium expansum)	[321]
	Chitosan/dextran NPs	100 µg m/L	Alfalafa mosaic virus on Nicotiana glutinosa plant	[322]
	Nickle chitosan nanocojugate	0.04 mg/mL	Fusarium rot of wheat	[323]
	Fluoroalkenyl-Grafted Chitosan Oligosaccharide Derivative	1 mg/mL	Root knot nematode (Meloidogyne incongita)	[324]
	Chitosan along with botanicals (Argemone mexicana L., Achyranthes aspera L., and Ricinus communis L.)	2500, 2000, 1500, 1000, and 500 ppm	Meloidogyne incongita in carrot	[325]
Zein NPs	Natamycin-loaded zein-casein NPs (N-Z/C NPs)	20 and 80 µg/m	Brown rot of peach (Monilinia fructicola)	[326]
	Carvacrol-loaded zein NPs	135 μg/mL and 270 μg/mL	Bacterial canker (Pseudomonas syringae) Fusarium wilt (Fusarium oxysporum)	[327]
	Natamycin-loaded zein NPs stabilized by carboxymethyl chitosan	10 mg/L	Postharvest gray mold, rot and mildew of strawberry	[313]
	Satureja montana Essential Oil in combination with zein NPs	1 mg/mL	Bacterial spot of tomato (Xanthomonas sp.)	[314]
	Rotenone loaded zein NPs	16 μg m/L 48 μg m/L	Pseudomonas syringae Fusarium oxysporum	[328]
PLGA NPs	CTAB-PLGA Curcumin NP	52.57 μg/mL and 44.67 μg/mL and 15 μg/mL	Pythium ultimum var. ultimum	[329]
	Poly (lactic-co-glycolic acid) NPs(PLGA NPs)	1.25–0.07 μg mL	Gray mold disease (Botrytis cinerea)	[330]
Alginate NPs	Alginate oligosaccharide (AOS) combined with Meyerozyma guilliermondii	5 g/L	Blue mold decay (Penicillium expansum)	[331]
	Alginate oligosaccharide (AOS)	50 mg/L	Gray mold of kiwi fruit (Botrytis cinerea)	[332]
	Alginate polysaccharide	1 g/L	Bayoud disease of date palm (Fusarium oxysporum f. sp. albedins)	[333]
	Alginate	2 g/L	Verticillium wilt of olive (Verticillium dahliae)	[334]
	Nano Cu-Cu2O/Alginate	17.8 mg Cu/L.	Rice blast (Pyricularia oryzae)	[335]

Table 8. Applications of carbon NPs in plant disease management.

Polymeric NPs	NPs Type	Concentration	Disease & Pathogen Management	References
Chitosan	Moringa chitosan NPs	200 mg/L	Rice blast (Magnoparthae oryzae)	[311]
	Chitosan in acetic acid distilled water solution	4 g/L	Dry rot and wilt (Fusarium sp.)	[312]
	Chitosan biopolymer	2.5 mg/mL	Powdery mildew of cucumber	[313,314]
	Chitosan	100 and 200 µg/mL	Bacterial wilt of potato and tomato	[315]
	Bioengineered chitosan iron nanocomposites	In vitro: 250 μg m/L In vivo: 250 μg m/L	Bacterial leaf blight of rice (Xanthomonas oryzae pv. oryzae)	[172]
	Chitosan	300 mg/L and 400 mg/L	Bean yellow mosaic virus of faba bean	[316]
	Chitosan composite film having chitosan, calcium, auxiliaries, ferulic acid and dextrin	0.71–1.42 g/L	Soft rot of kiwi (B. dothidea and Phomopsis sp.)	[317]
	Copper chitosan NPs	0.10, 0.20, and 0.30 mg/mL	Fusarium wilt of banana (Fusarium oxysporum f. sp. cubense)	[318]
	Chitosan	0.1–2.0 g/L	Root rot of fenugreek (Fusarium solani)	[319]
	Chitosan	500 mg/L	Powdery mildew of Rosa roxburghii	[320]
	Chitosan	0.2 g/L and 0.4 g/L	Blue mold of apple (Penicillium expansum)	[321]
	Chitosan/dextran NPs	100 µg m/L	Alfalafa mosaic virus on Nicotiana glutinosa plant	[322]
	Nickle chitosan nanocojugate	0.04 mg/mL	Fusarium rot of wheat	[323]
	Fluoroalkenyl-Grafted Chitosan Oligosaccharide Derivative	1 mg/mL	Root knot nematode (Meloidogyne incongita)	[324]
	Chitosan along with botanicals (Argemone mexicana L., Achyranthes aspera L., and Ricinus communis L.)	2500, 2000, 1500, 1000, and 500 ppm	Meloidogyne incongita in carrot	[325]
Zein NPs	Natamycin-loaded zein-casein NPs (N-Z/C NPs)	20 and 80 µg/m	Brown rot of peach (Monilinia fructicola)	[326]
	Carvacrol-loaded zein NPs	135 μg/mL and 270 μg/mL	Bacterial canker (Pseudomonas syringae) Fusarium wilt (Fusarium oxysporum)	[327]
	Natamycin-loaded zein NPs stabilized by carboxymethyl chitosan	10 mg/L	Postharvest gray mold, rot and mildew of strawberry	[313]
	Satureja montana Essential Oil in combination with zein NPs	1 mg/mL	Bacterial spot of tomato (Xanthomonas sp.)	[314]
	Rotenone loaded zein NPs	16 μg m/L 48 μg m/L	Pseudomonas syringae Fusarium oxysporum	[328]
PLGA NPs	CTAB-PLGA Curcumin NP	52.57 μg/mL and 44.67 μg/mL and 15 μg/mL	Pythium ultimum var. ultimum	[329]
	Poly (lactic-co-glycolic acid) NPs(PLGA NPs)	1.25–0.07 μg mL	Gray mold disease (Botrytis cinerea)	[330]
Alginate NPs	Alginate oligosaccharide (AOS) combined with Meyerozyma guilliermondii	5 g/L	Blue mold decay (Penicillium expansum)	[331]
	Alginate oligosaccharide (AOS)	50 mg/L	Gray mold of kiwi fruit (Botrytis cinerea)	[332]
	Alginate polysaccharide	1 g/L	Bayoud disease of date palm (Fusarium oxysporum f. sp. albedins)	[333]
	Alginate	2 g/L	Verticillium wilt of olive (Verticillium dahliae)	[334]
	Nano Cu-Cu2O/Alginate	17.8 mg Cu/L.	Rice blast (Pyricularia oryzae)	[335]

2.5. Limitations of Nanotechnology

Nanotechnology is considered a groundbreaking technology that holds the potential to revolutionize numerous industries, including agriculture. Despite its promising applications, it also carries a number of possible risks and drawbacks [336]—as illustrated in Figure 9—that should be addressed. One of the major concerns is their nano-scale size, which enables them to be easily transported by air and water, thereby causing contamination. Once released in the environment, their accumulation in the air, water and soil leads to the development of ecological threats. For instance, a disruption of the balance of macro- and microorganisms leads to a decrease in soil fertility [337,338,339]. Nanopesticides can enhance the efficiency of pesticides by providing controlled release to the targeted pathogens. However, several studies have shown that only 0.1% of nanopesticides reach the intended target, while the remaining 99.9% disperse in the surrounding environment, which results in the loss of biodiversity, soil and water pollution and increased resistance among plant pests and pathogens. Studies have shown that nanopesticides are harmful to bees, which are important pollinators for the spread of pollen [36]. Additionally, their accumulation in plants and animals have adverse impacts on human health [340], leading to cardiovascular issues, respiratory diseases and neurological damage as well [341]. Direct exposure to nanopesticides through the skin facilitates their entry into systemic circulation, which causes systemic toxicity [342]. The interaction of NPs with cellular components, such as nucleic acid, lipids, proteins etc., causes inflammation, toxicity and oxidative stress [343]. As a result, reactive oxygen species (ROS) are produced in the body that damage the cellular membranes [344]. Furthermore, substantial investment is required for the research and development of nanotechnology, making it expensive. It is unaffordable for small scale growers, resulting in an unequal distribution of the benefits of nanotechnology in society [336]. Finally, last but not least, there is a knowledge gap regarding the environmental and ecosystem impacts of nanotechnology, which justifies significant investment to mitigate the potential hazards these tiny particles represent to humans and wildlife [345].

3. Conclusions

In conclusion, the integration of nanotechnology into plant disease management represents a promising pathway for sustainable agriculture. As traditional methods face numerous increasing challenges, such as pesticide resistance and environmental concerns, nanotechnology offers innovative solutions for enhanced disease resistance, controlled drug delivery and reduced pest resistance. NPs bring the promising benefit of targeted delivery to enhance the plant defense mechanism.

However, there are certain obstacles to the adoption of nanotechnology. Concerns regarding NPs toxicity, regulatory frameworks and environmental persistence demands thorough investigation and careful consideration. Collaborative efforts between researchers, policymakers and industry stakeholders are imperative to address these challenges and to ensure the safe application of nanotechnology in agriculture.

Despite these challenges, the potential benefits of nanotechnology in plant disease management are vast. By utilizing nanoscale materials and technologies, farmers can mitigate the impacts of plant disease by promoting sustainable agriculture. In addition, genetic engineering technologies also play a crucial role in developing disease-resistant crops, offering complementary and powerful tools to enhance crop resilience. Continued research, coupled with protective measures to address regulatory concerns and safety measures, will be essential in understanding the full potential of nanotechnology to revolutionize modern agriculture and ensure global food security for future generations.

Future Directions

Nanotechnology can offer vast and promising applications in plant disease management. One of its exciting domains of exploration is the development of multi-functional NPs or nanocomposites that can detect, treat and deliver drugs and nutrients simultaneously to plants to improve plant health status. Additionally, the development of advanced nanocarrier systems designed for the targeted delivery of treatments to specific plant pathogens holds great potential. This system would enable precise application, reducing the impact on non-target organisms and decreasing the reliance on chemical pesticides. Furthermore, the development of nanosensors for the real-time monitoring of plant health and early disease detection is a critical area for future research directions. Such technology would allow for timely interventions, improving management practices and potentially preventing large scale disease outbreaks. These future directions highlight the transformative potential of nanotechnology in creating more efficient, sustainable and effective plant disease management strategies.

Challenges: The challenges in genome editing include handling the off-target effects, improving delivery methods for CRISPR components, and addressing ethical issues related to safety and use. Regulatory concerns focus on ensuring the safety and effectiveness of genome-edited products and managing public perception. These concerns can differ by region and impact how genome editing technologies are developed, approved, and adopted.