[Behavioral response and adaptive cost in resistant and susceptible Plutella xylostella to Chlorantraniliprole]

Characterization of Triadica sebifera (L.) Small Extracts, Antifeedant Activities of Extracts, Fractions, Seed Oil and Isolated Compounds against Plutella xylostella (L.) and Their Effect on Detoxification Enzymes

Plutella xylostella L. is one of the world’s major pests of cruciferous crops. The indiscriminate use of synthetic insecticides has led to insecticide resistance and resurgence, and has been harmful to non-target organisms and the environment. Botanical insecticides are the best alternatives to synthetic pesticides for the management of pests in organic agriculture and integrated management. T. sebifera is an invasive species and has good potential as an insecticide due to the availability of plant material in some parts of India. The antifeedant activities of T. sebifera have not been reported against P. xylostella and other lepidopteron insects to date. Therefore, the current study targeted the characterization of leaf and bark extracts, feeding deterrence, synergistic and detoxification enzyme activities of leaf/bark ethanolic extracts/fractions, seed oil, and isolated compounds. UHPLC-QTOF-IMS analysis showed that shikimic acid, xanthoxylin, quercetin, kaempferol, methyl gallate, and stigmasterol are common metabolites identified in leaf and bark extracts. The combination of seed oil with bark extract showed higher deterrence (DC₅₀ = 317.10 mg/L) as compared to leaf/bark extracts alone. Gallic acid showed higher deterrence (67.48%) than kaempferol and quercetin. The n-butanol fraction of bark was more repellent (RC₅₀ = 414.61 mg/L). Based on DC₅₀, the seed oil with leaf extract (1:1 ratio) alone with choice and seed oil with leaf and bark extract without choice showed synergistic interaction, but seed oil with bark extract with choice showed additive interaction. The ethanol extract of leaf, bark, and seed oil inhibited GST and AChE in P. xylostella. The leaf extract and seed oil or their combinations may be recommended as antifeedants to reduce damage by P. xylostella based on persistence, antifeedant, phytotoxicity, safety to predators/parasitoids, etc., under field conditions.

Extraction and determination of flubendiamide insecticide in food samples: A review

Flubendiamide (FBD) is the first commercially available phthalic acid diamide that targets ryanodine receptors (RyRs) in insects, which play a major role in lepidoptera control. However, excessive use of FBD can influence the quality of treated products leading to toxic effects on human health. The availability of rapid and convenient methods for evaluating FBD amount in the environment is necessary. Therefore, analytical methods were developed for the determination of residues of FBD and its metabolite desiodo in different food matrices like tomato, cabbage, pigeon pea, apple, chilli and rice. The current review carries forward methods for FBD residues analysis in foods by using several chromatographic techniques including sample preparation steps. The comparison between the different methods employed for quantitative and qualitative analysis of food quality and safety is also discussed. Liquid chromatography (LC) is the predominant analytical method for assessing the quality of foods treated with FBD. Studies related to LC coupled multichannel detector (Ultraviolet (UV), Mass spectrometry (MS)) are also applied to detect pesticide residues. Extraction and clean up steps are essential to obtain reliable results. Moreover, this review reports the allowed limits of residues for the safety of consuming products treated with FBD.

Fitness Costs of Chlorantraniliprole Resistance Related to the SeNPF Overexpression in the Spodoptera exigua (Lepidoptera: Noctuidae)

Spodopteraexigua, a multifeeding insect pest, has developed a high level of resistance to chlorantraniliprole, which is a benzoylurea insecticide that targets the ryanodine receptors (RyRs). Herein, the resistant strain (SE-Sel) and sensitive strain (SE-Sus) were obtained by bidirectional screening for six generations. The potential oviposited eggs and oviposition rate of the SE-Sel strain were dramatically lower than those of the SE-Sus strain; on the contrary, the weights of prepupae and preadult were significantly increased. As a post-mating response, the higher number of non-oviposited eggs in the SE-Sel strain was caused by a lower mating rate. In addition, the expression levels of vitellogenin (SeVg) and its receptor (SeVgR) in the SE-Sel strain were consistently lower than those in the SE-Sus strain. An RyR^I4743M mutation, contributing to the resistance to chlorantraniliprole, was located in the S3 transmembrane segments and might have affected the release of calcium ions; it led to the upregulated expression of the neuropeptide SeNPF and its receptor SeNPFR, and the mating and oviposition rate were significantly recovered when the SeNPF was knocked down though RNA interference (RNAi) in the male adult of the SE-Sel strain. Moreover, the expression of the juvenile hormone-binding proteins SeJHBWDS3 and SeJHBAN in the male adult of the SE-Sel strain was significantly decreased, which proved the existence of a fitness cost from another angle. Therefore, these results indicate that the fitness cost accompanied by chlorantraniliprole resistance in S. exigua may be related to the decrease in mating desire due to SeNPF overexpression.

Insecticidal activity of the extract, fractions, and pure steroidal saponins of Trillium govanianum Wall. ex D. Don for the control of diamondback moth (Plutella xylostella L.) and aphid (Aphis craccivora Koch)

BACKGROUND

Plutella xylostella L. is the major pest of crucifers globally, causing significant yield loss. Aphis craccivora Koch is the main sucking pest of legumes that transmit viral diseases, leading to economic yield reduction. To minimize loss due to pests, farmers/growers use synthetic insecticides frequently for their control, which led to insecticide resistance, detrimental to natural enemies of pest, environment, etc. Therefore, in this study, the insecticidal activity of plant extract, fractions, and pure steroidal saponins from Trillium govanianum was evaluated for their bio-efficacy against targeted pests.

RESULTS

Parent extract was found more effective (LC₅₀ = 1541.2 mg L^-1 ) against larvae of P. xylostella after 96 h than n-butanol, n-hexane, and ethyl acetate fractions (LC₅₀ = 3030, 3578 and 3878.1 mg L^-1 , respectively). For A. craccivora, ethyl acetate fraction (LC₅₀ = 2186.3 mg L^-1 ) was most effective after 96 h than n-hexane fraction (LC₅₀ = 2234.6 mg L^-1 ), n-butanol fraction (LC₅₀ = 2696.3 mg L^-1 ) and parent extract (LC₅₀ = 3709.1 mg L^-1 ). Among pure molecules, govanoside B was found more effective (76% mortality, LC₅₀ = 3279.5 mg L^-1 ) followed by borassoside E (74%, LC₅₀ = 3467.1 mg L^-1 ) against A. craccivora after 96 h.

CONCLUSION

Parent extract/fractions of T. govanianum showed promising efficacy against larvae of P. xylostella and A. craccivora. Further, field study is required for its bio-efficacy against targeted pests for validation and formulation development.