Do fall armyworm’s Metaflumizone resistante populations affect the activity of Trichogramma pretiosum?

Abstract

The possible interference of resistant pest’s populations to insecticides in natural enemies in the action thas not been clarified yet. Thus, this study aimed to evaluate Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) performance on Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) eggs with resistance frequency to the Metaflumizone over six generations of product exposure. Egg cards (2.0 x 7.0 cm) containing eggs from two populations of S. frugiperda, (resistant to Metaflumizone and the other susceptible), were exposed to T. pretiosum females for 24 hours in free-choice and no-choice testing in three generations (G1, G4, and G6). A completely randomized experimental design was used with 25 replications, each consisting of an egg card (experimental unit) containing 20 eggs. The parameters evaluated were: parasitism (%), emergence (%), sex ratio, number of emerged parasitoids per egg and males/females longevity. ANOVA and Tukey test (P≤ 0.05) were applied on the results. Results showed a reduction in parasitism [41.0% (G1) and 28.4% (G4)], egg emergence (17.5%) and parasitoids/egg [16.2 (G4) and 17.2 (G6)] in eggs originating from the population with resistance frequency. Females emerging from G6 populations eggs without exposure to Metaflumizone had greater longevity (3.5 days more) than the resistant population. The sex ratio and male longevity were not affected. The results indicate a reduction in T. pretiosum activity if S. frugiperda populations have some frequency of resistance to Metaflumizone.

Fitness costs of resistance to insecticides in insects

“…The interference identified in the performance of T. pretiosum emphasizes the necessity of understanding how improper insecticide use can harm the fitness of the natural enemy. On the other hand, T. pretiosum can still be utilized in IPM management programs since it maintains its effectiveness even in the presence of resistant populations in the field whenever host eggs of S. frugiperda populations had some resistance when over six generations of exposure to metaflumizone, the biological activity of T. pretiosum was decreased ( Barbosa et al, 2021 ). It was discovered that eggs originating from the resistant population had lower parasitism percentages, emergence, and parasitoids/eggs, but females from the susceptible population survived longer than those from the resistant population.…”