Toxicity of Phenyl Isothiocyanate and Its Sublethal Effects on Growth, Development and Oviposition in Bt-Susceptible and Bt-Resistant Pink Bollworms

Pest development of resistance to Bacillus thuringiensis (Bt) insecticidal proteins threatens the sustainability of Bt crops, and it is therefore necessary to explore ecofriendly alternative insecticides for controlling Bt-resistant populations. Isothiocyanates are plant secondary metabolites that exhibit a diverse array of types and resistance against a broad spectrum of insect pests, but their effects on pink bollworms remain unexplored. Here, we evaluated the effects of phenyl isothiocyanate on Bt-susceptible and Bt-resistant pink bollworms (Pectinophora gossypiella). The LC₅₀ values of phenyl isothiocyanate for Bt-susceptible and Bt-resistant larvae were 26.4 and 28.6 μg/mL, respectively. The LC₃₀ sublethal dose of phenyl isothiocyanate significantly impaired the 7-day larval survival, the pupation rate, neonate-to-adult survival, the pupal weight, eggs per female and the egg hatching rate and prolonged the larval developmental period but not pupal duration for both strains. The response to phenyl isothiocyanate ingestion did not differ significantly between the two strains, implying that the Bt-resistant strain did not possess cross-resistance to phenyl isothiocyanate. These results provide scientific evidence for enriching green control technologies, resistance management tactics and comprehensive management measures for pink bollworm.