Lethal and sublethal effects of chlorantraniliprole on the migratory moths Agrotis ipsilon and A. segetum: New perspectives for pest management strategies

Unclassified glutathione-S-transferase AiGSTu1 confers chlorantraniliprole tolerance in Agrotis ipsilon

BACKGROUND

Chlorantraniliprole (CAP) is a diamide insecticide with high efficacy against many pest insects, including the black cutworm, Agrotis ipsilon. Agrotis ipsilon is a serious pest causing significant yield losses in crops. Glutathione-S-transferases (GSTs) belong to a family of metabolic enzymes that can detoxify a wide range of pesticides. However, little is known about the functions of GSTs in CAP tolerance in A. ipsilon.

RESULTS

A cDNA sequence (designated AiGSTu1) encoding an unclassified GST was identified from A. ipsilon. AiGSTu1 is highly expressed during the 3rd -instar larval and the pupal stages. Most of the mRNA transcripts were found in larval Malpighian tubules. Exposure to CAP strongly enhanced AiGSTu1 expression, GST activity, hydrogen peroxide (H2 O2 ) and malondialdehyde levels in larvae. H2 O2 treatment upregulated the transcription level of AiGSTu1, suggesting that CAP-induced oxidative stress may activate AiGSTu1 expression. The activity of recombinant AiGSTu1 was inhibited by CAP in a dose-dependent manner. Metabolism assay results demonstrated that AiGSTu1 is capable of depleting CAP. Overexpression of AiGSTu1 enhanced the tolerance of Escherichia coli cells to H2 O2 and the oxidative stress inducer, cumene hydroperoxide. Silencing of AiGSTu1 by RNA interference increased the susceptibility of A. ipsilon larvae to CAP.

CONCLUSION

The findings of this study provide valuable insights into the potential role of AiGSTu1 in CAP detoxification and will improve our understanding of CAP tolerance in A. ipsilon. © 2023 Society of Chemical Industry.

Lethal and sublethal effects of broflanilide on four tephritid pests (Diptera: Tephritidae)

BACKGROUND

Fruit flies are internationally important quarantine or invasive pests of many fruits and vegetables and can cause serious economic losses. Long-term reliance on insecticides for controlling these pests has led to increasing resistance to multiple insecticides; hence, a new agent is needed. In this study, the acute toxicity and sublethal effects of the novel insecticide broflanilide on four adult fruit fly species, Bactrocera dorsalis, Bactrocera cucurbitae, Bactrocera tau, and Bactrocera correcta, were evaluated.

RESULTS

Broflanilide was effective against B. dorsalis and B. correcta, with lethal concentration values (amount required to kill 50% of animals; LC₅₀ ) of 0.390 and 1.716 mg/L. However, for B. cucurbitae (19.673 mg/L) and B. tau (24.373 mg/L), the LC₅₀ was 50-60 times higher than that of B. dorsalis. The survival rates of B. correcta and B. cucurbitae were significantly lower under LC₅₀ treatment than those of the control (corrected for mortality rate). Sublethal concentrations of broflanilide stimulated fecundity in all species except B. tau. The hatching rate at LC₅₀ was significantly lower for B. correcta and B. tau compared with the control and even more so for B. correcta, which was zero.

CONCLUSION

Broflanilide is potentially an effective insecticide for controlling B. dorsalis and B. correcta. However, the variation in toxicity of broflanilide to the four fruit flies suggests that species variation needs to be carefully considered. Our results highlight the importance of clarifying the sublethal effects of insecticides on target insects to ensure the comprehensive evaluation and rational use of insecticides. © 2023 Society of Chemical Industry.

The Comparative Toxicity, Biochemical and Physiological Impacts of Chlorantraniliprole and Indoxacarb on Mamestra brassicae (Lepidoptera: Noctuidae)

BACKGROUND

The cabbage moth, Mamestra brassicae, is a polyphagous pest that attacks several crops. Here, the sublethal and lethal effects of chlorantraniliprole and indoxacarb were investigated on the developmental stages, detoxification enzymes, reproductive activity, calling behavior, peripheral physiology, and pheromone titer of M. brasssicae. Methods: To assess pesticide effects, the second instar larvae were maintained for 24 h on a semi-artificial diet containing insecticides at their LC₁₀, LC₃₀, and LC₅₀ concentrations.

RESULTS

M. brassicae was more susceptible to chlorantraniliprole (LC₅₀ = 0.35 mg/L) than indoxacarb (LC₅₀ = 1.71 mg/L). A significantly increased developmental time was observed with both insecticides at all tested concentrations but decreases in pupation rate, pupal weight, and emergence were limited to the LC₅₀ concentration. Reductions in both the total number of eggs laid per female and the egg viability were observed with both insecticides at their LC₃₀ and LC₅₀ concentrations. Both female calling activity and the sex pheromone (Z11-hexadecenyl acetate and hexadecenyl acetate) titer were significantly reduced by chlorantraniliprole in LC₅₀ concentration. Antennal responses of female antennae to benzaldehyde and 3-octanone were significantly weaker than controls after exposure to the indoxocarb LC₅₀ concentration. Significant reductions in the enzymatic activity of glutathione S-transferases, mixed-function oxidases, and carboxylesterases were observed in response to both insecticides.

Preparation of a broad-specific monoclonal antibody and development of an immunochromatographic assay for monitoring of anthranilic diamides in vegetables and fruits

A mAb-based lateral flow immunochromatographic strip for the detection of anthranilic diamides in vegetables and fruits was developed. The strip provided cut-off values of 2.5, 5, 10, and 10 ng g−1 for CHL, CYA, CYC, and TEA, respectively.