Search Results (10)

Cauliflower, a widely cultivated vegetable crop valued for its edible curds, faces a persistent threat from insect pests, which are typically managed using synthetic insecticides. This study evaluated the benefits of intercropping practices as part of an ecological pest management strategy in cauliflower cultivation during the winter seasons of 2017–18 and 2021–22. Nine insect pests belonging to six families of three orders were recorded. The calendula intercropping system (IS) consistently showed the lowest infestation by Plutella xylostella and Pieris brassicae/plant. Calendula IS had attracted the highest numbers of syrphids, Cotesia glomerata, Diaeretiella rapae, Cotesia vestalis, and coccinellids such as Coccinella septempunctata and Cheilomenes sexmaculata. In candytuft IS, a strong tri-trophic interaction between the flower and D. rapae significantly reduced aphid populations, for each additional D. rapae, aphid numbers decreased by 48.53 in 2018. The marigold IS recorded the highest Shannon diversity index in 2021–22. The longest adult survival of C. septempunctata (8.67 ± 3.35 days), in the absence of aphids was recorded on candytuft flowers. The total sugars and protein in flowers positively influenced the longevity of the adult coccinellid beetles (R²-40.42 and 20.79%, respectively). Calendula intercropping yielded the highest revenue return of Indian rupee (₹) 11.33 per INR 1 invested, compared to the cauliflower monocrop (1.58). These findings demonstrate that, intercropping and habitat manipulation can enhance ecological pest control and reduce the dependence on synthetic chemicals. Full article

Volatile plant compounds are essential for host plant selection by herbivores and particularly important for the behaviour of parasitoids seeking larvae in which to lay eggs. Headspace extracts were collected from intact plants of four Brassica oleracea genotypes, as well as from plants damaged by larvae of Mamestra brassicae or Pieris rapae. In total, 52 volatiles present in the headspaces of four genotypes were selected for multivariate analyses. The most abundant groups of volatiles were terpenes and esters, represented by 20 and 14 compounds, respectively. The qualitative and quantitative differences in odour profiles between the four genotypes were sufficient to differentiate between groups using multivariate analysis techniques. The most distinct volatile blends originated from curly kale, followed by cabbage, cauliflower and broccoli. Multivariate analysis revealed that genotypes affected the composition of the volatile blends to a large extent compared to the herbivore damage by the different species tested. In curly kale, broccoli and cauliflower, the differences in odour bouquets were more expressed between plants with and without active feeding, independent of the herbivore identity, while in cabbage, larger differences were observed between odour profiles with different herbivore feedings, independent of whether the herbivore was present or removed. Full article

The cabbage butterfly, Pieris brassicae Linnaeus (Lepidoptera: Pieridae), is an oligophagous and invasive insect pest of various economically important cole crops. Recently, there have been reports about an increase in the incidence and damaging activities of cabbage butterflies, signifying that the existing control methods fail to meet the grower’s expectations. Entomopathogenic nematodes (EPNs) and their endosymbiotic bacteria have immense potential for the control of a wide range of insect pests. In this investigation, the EPN species Steinernema carpocapsae and its associated bacterial species, Xenorhabdus nematophila, were isolated and identified through morphological and molecular techniques. The laboratory bioassay experiment was performed using S. carpocapsae and X. nematophila against the 3rd instar larvae of P. brassicae (25 ± 1 °C; RH = 60%). The efficacy of EPN suspension (30, 60, 90, 120, 150 IJs/mL) and bacterial suspension (1 × 10⁴, 2 × 10⁴, 3 × 10⁴, 4 × 10⁴, and 5 × 10⁴ CFU/mL) via contact and oral routes showed significant mortality among the larvae. Surprisingly, 100% insect mortality within 48 h was recorded in the bacterial inoculum 5 × 10⁴ CFU/mL. However, in the case of EPNs (S. carpocapsae), 150 IJs/mL caused the highest, 92%, larval mortality rate after 96 h. The results signify that both indigenous EPNs and their associated bacteria can provide efficient control against P. brassicae larvae and could effectively contribute to IPM programs. However, further analyses are required to authenticate their effectiveness in field conditions. Full article

Size and shape are important determinants of fitness in most living beings. Accordingly, the capacity of the organism to regulate size and shape during growth, containing the effects of developmental disturbances of different origin, is considered a key feature of the developmental system. In a recent study, through a geometric morphometric analysis on a laboratory-reared sample of the lepidopteran Pieris brassicae, we found evidence of regulatory mechanisms able to restrain size and shape variation, including bilateral fluctuating asymmetry, during larval development. However, the efficacy of the regulatory mechanism under greater environmental variation remains to be explored. Here, based on a field-reared sample of the same species, by adopting identical measurements of size and shape variation, we found that the regulatory mechanisms for containing the effects of developmental disturbances during larval growth in P. brassicae are also effective under more natural environmental conditions. This study may contribute to better characterization of the mechanisms of developmental stability and canalization and their combined effects in the developmental interactions between the organism and its environment. Full article

Diamondback moth (DBM), Plutella xylostella, and imported cabbage worm (ICW), Pieris rapae, are destructive pests of crucifers worldwide. Although several insecticides are effective against ICW, pesticide management against DBM is challenged by insecticide resistant populations. The objective of this study was to explore the potential of integrating foliar sprays of the entomopathogenic nematode (EPN) Steinernema feltiae with trap cropping using kai choi (Brassica juncea) planted as an intercrop for the management of DBM and ICW. Four 2 × 2 (trap crop × EPN) factorial designed field trials were conducted with 2 trials on head cabbage (Brassica oleraceae var capitata) and 2 on kale (Brassica oleraceae var acephala). In the first head cabbage trial, trap cropping reduced DBM abundance by 46% and ICW abundance by 73%. Leaf damage by DBM and ICW were reduced by 45% and 33%, respectively. In the second head cabbage trial, DBM populations were reduced by 19% whereas ICW was reduced by 65%. No effects were observed on leaf damage. Trap cropping suppressed DBM abundance by 50% and DBM leaf damage by 19% in the first kale trial. No significant effects were observed on ICW. In the second kale trial, trap cropping reduced ICW leaf damage by 13%. In the first head cabbage trial, adding EPN foliar sprays further reduced DBM populations in plots with trap crops and ICW in plots without trap crops. In the second kale trial, EPNs suppressed DBM populations entirely. No effects from EPNs were observed in the second head cabbage trial or the first kale trial. It is concluded that trap cropping with kai choi did not improve the efficacy of EPN foliar sprays consistently. EPNs were most successful at suppressing DBM and ICW populations when the average pest pressure was below 0.5/plant whereas trap crops worked more effectively at insect populations above 0.5/plant. Although the use of trap cropping reduced pest abundance and leaf damage, the weight of head cabbage and kale was lower when planted 30 cm or closer to kai choi plants. This was resolved by leaving a distance of 60 cm between cash and trap crops. With further optimization, the use of trap cropping and EPN foliar sprays can be beneficial to an integrated pest management program to control DBM and ICW in cruciferous crops. Full article

The most common destructive insect pests affecting cabbages in African smallholder farmers include Plutella xylostella, Helula undalis, Pieris brassicae, Brevycoryne brassicae, Trichoplusia ni and Myzus persicae. Those insect pests infest cabbages at different stages of growth, causing huge damage and resulting into huge yield losses. The African smallholder farmers use cultural and synthetic pesticides to control insect pests and minimize infestations. The cultural practices like crop rotation, weeding and handpicking are used to minimize the invasion of cabbage pests. However, those practices are not sufficiently enough to control cabbage insect pests although they are cheap and safe to the environment. Also, the African smallholder famers rely intensively on the application of broad-spectrum of synthetic pesticides to effectively control the cabbage pests in the field. Due to severe infestation of cabbages caused by those insects, most of African smallholder farmers decide to; first, increase the concentrations of synthetic pesticides beyond the recommended amount by manufacturers. Secondly, increase the rate of application of the synthetic pesticides throughout the growing season to effectively kill the most stubborn insect pests infesting cabbages (Brassica oleracea var. capitata). Thirdly, they mix more than two synthetic pesticides for the purpose of increasing the spectrum of killing the most stubborn insect pests in the field. All those scenarios intensify the environmental pollution especially soil and water pollution. Moreover, most of insecticides sprayed are made with broad-spectrum and are hazardous chemicals posing environmental pollution and threats to natural enemies’ ecosystems. Therefore, this paper reviews Brassica oleracea var. capitata insect pests and control measures as a potential environmental pollution threat in African smallholder farmers. Full article

Crops, such as white cabbage (Brassica oleracea L. var. capitata (L.) f. alba), are often infested by herbivorous insects that consume the leaves directly or lay eggs with subsequent injury by caterpillars. The plants can produce various defensive metabolites or free radicals that repel the insects to avert further damage. To study the production and effects of these compounds, large white cabbage butterflies, Pieris brassicae and flea beetles, Phyllotreta nemorum, were captured in a cabbage field and applied to plants cultivated in the lab. After insect infestation, leaves were collected and UV/Vis spectrophotometry and HPLC used to determine the content of stress molecules (superoxide), primary metabolites (amino acids), and secondary metabolites (phenolic acids and flavonoids). The highest level of superoxide was measured in plants exposed to fifty flea beetles. These plants also manifested a higher content of phenylalanine, a substrate for the synthesis of phenolic compounds, and in activation of total phenolics and flavonoid production. The levels of specific phenolic acids and flavonoids had higher variability when the dominant increase was in the flavonoid, quercetin. The leaves after flea beetle attack also showed an increase in ascorbic acid which is an important nutrient of cabbage. Full article

Variation in local herbivore pressure along elevation gradients is predicted to drive variation in plant defense traits. Yet, the extent of intraspecific variation in defense investment along elevation gradients, and its effects on both herbivore preference and performance, remain relatively unexplored. Using populations of Arabidopsis halleri (Brassicaceae) occurring at different elevations in the Alps, we tested for associations between elevation, herbivore damage in the field, and constitutive chemical defense traits (glucosinolates) assayed under common-garden conditions. Additionally, we examined the feeding preferences and performance of a specialist herbivore, the butterfly Pieris brassicae, on plants from different elevations in the Alps. Although we found no effect of elevation on the overall levels of constitutive glucosinolates in leaves, relative amounts of indole glucosinolates increased significantly with elevation and were negatively correlated with herbivore damage in the field. In oviposition preference assays, P. brassicae females laid fewer eggs on plants from high-elevation populations, although larval performance was similar on populations from different elevations. Taken together, these results support the prediction that species distributed along elevation gradients exhibit genetic variation in chemical defenses, which can have consequences for interactions with herbivores in the field. Full article

Experience of insect herbivores and their natural enemies in the natal habitat is considered to affect their likelihood of accepting a similar habitat or plant/host during dispersal. Growing phenology of food plants and the number of generations in the insects further determines lability of insect behavioural responses at eclosion. We studied the effect of rearing history on oviposition preference in a multivoltine herbivore (Pieris brassicae), and foraging behaviour in the endoparasitoid wasp (Cotesia glomerata) a specialist enemy of P. brassicae. Different generations of the insects are obligatorily associated with different plants in the Brassicaceae, e.g., Brassica rapa, Brassica nigra and Sinapis arvensis, exhibiting different seasonal phenologies in The Netherlands. Food plant preference of adults was examined when the insects had been reared on each of the three plant species for one generation. Rearing history only marginally affected oviposition preference of P. brassicae butterflies, but they never preferred the plant on which they had been reared. C. glomerata had a clear preference for host-infested B. rapa plants, irrespective of rearing history. Higher levels of the glucosinolate breakdown product 3-butenyl isothiocyanate in the headspace of B. rapa plants could explain enhanced attractiveness. Our results reveal the potential importance of flexible plant choice for female multivoltine insects in nature. Full article

This study aims to evaluate the antioxidant potential of extracts of Brassica oleracea L. var. acephala DC. (kale) and several materials of Pieris brassicae L., a common pest of Brassica cultures using a cellular model with hamster lung fibroblast (V79 cells) under quiescent conditions and subjected to H₂O₂-induced oxidative stress. Cytotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay and glutathione was determined by the 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB)-oxidized glutathione (GSSG) reductase recycling assay. The phenolic composition of the extracts was also established by HPLC-DAD. They presented acylated and non acylated flavonoid glycosides, some of them sulfated, and hydroxycinnamic acyl gentiobiosides. All extracts were cytotoxic by themselves at high concentrations and failed to protect V79 cells against H₂O₂ acute toxicity. No relationship between phenolic composition and cytotoxicity of the extracts was found. Rather, a significant increase in glutathione was observed in cells exposed to kale extract, which contained the highest amount and variety of flavonoids. It can be concluded that although flavonoids-rich extracts have the ability to increase cellular antioxidant defenses, the use of extracts of kale and P. brassicae materials by pharmaceutical or food industries, may constitute an insult to health, especially to debilitated individuals, if high doses are consumed. Full article