Assessment of insecticide mortality on fall armyworm (Spodoptera frugiperda) between locations and modes of insecticide entry

Abstract

Spodoptera frugiperda is a major pest of maize and plants expressing insecticide proteins from Bacillus thuringiensis. Control programs based on Bt maize events have increased inefficacy for this pest, often demanding insecticide sprays as a complementary measure. The aim of this work was to evaluate larval mortality in two S. frugiperda populations submitted to different insecticide sprays and modes of entry into the insect’s body. Experimental design was completely randomized with a factorial scheme 4×2×2, plus one check. Four insecticides [azadirachtin (12 g a.i. L-1), lambda-cyhalothrin (50 g a.i. L-1), teflubenzuron (150 g a.i. L-1), flubendiamide (480 g a.i. L-1)], two modes of entry for each insecticide (topic contact and ingestion) and two S. frugiperda populations (from Constantina and Sertão) were tested. The mortality of individuals was assessed daily for 15 days after treatment spraying. The insecticides teflubenzuron and flubendiamide presented the highest mortality levels of S. frugiperda, disregarding the differences between tested populations and modes of entry. Contamination by ingestion resulted in higher mortality, especially for teflubenzuron and flubendiamide. The results suggest that S. frugiperda from Constantina are less susceptible to the insecticides evaluated.