Effects of difenoconazole and pyraclostrobin on the development, reproduction, and detoxifying metabolism of Spodoptera frugiperda (J.E. Smith)

Abstract

Spodoptera frugiperda (J.E. Smith) is a major insect pest affecting corn globally. S. frugiperda often coincides with maize diseases, as their damage periods overlap. Consequently, S. frugiperda may be exposed to varying types and quantities of these fungicides during the growing season. The aim of this study was to determine the effects of difenoconazole and pyraclostrobin on the biological and physiological traits of S. frugiperda. Treatment with difenoconazole and pyraclostrobin significantly prolonged the pupal development period in the F0 generation of S. frugiperda compared to the control group. Additionally, exposure to difenoconazole shortened the development periods of the 1st and 6th instar larvae and reduced the adult preoviposition period (APOP) in the F1 generation of S. frugiperda. However, it extended the development period of the 4th instar larvae and pupae, as well as overall longevity. The pyraclostrobin treatment group exhibited a shorter development period of 2nd instar larvae, as well as longer longevity, and more eggs/per female in the F1 generation of S. frugiperda. Compared to the control group, the fecundity of the offspring of the pyraclostrobin treatment group increased by 68.24%. Furthermore, treatment with difenoconazole and pyraclostrobin significantly increased the intrinsic rate of increase (r) and the finite rate of increase (λ) in the F1 generation of S. frugiperda, while significantly reducing the mean generation time (T). Additionally, mRNA expression levels of CYP6AN4, CYP340L1, CYP321A10, CYP341A11, GST19, GST22, CE13059, CXE23, ABC01998, ABC18240, and UGT17742 were significantly elevated in F0 individuals from larvae treated with difenoconazole. Meanwhile, the relative expression levels of CYP6AN4, CYP340L1, CYP314A1, GST19, GST22, CE13095, CXE20, ABC01998, ABC18240, ABC22158, and ABC22158 in the larvae (F0) exposed to pyraclostrobin were also elevated. Compared to the control and difenoconazole treatment groups, the expression of the vitellogenin gene (Vg) and vitellogenin receptor (VgR) was significantly upregulated after pyraclostrobin treatment. The effects of difenoconazole and pyraclostrobin on the biological and reproductive performance of S. frugiperda could aid in optimizing the management strategies for this insect species.