ADULT-STAGE EXPRESSION OF EMAMECTIN BENZOATE RESISTANCE IN Spodoptera frugiperda (J. E. SMITH) FOLLOWING ORAL EXPOSURE

Abstract

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), has developed resistance to insecticides, including emamectin benzoate (EB). Most EB resistance studies use larval assays, whereas expression remains less characterized. We evaluated adult responses to exposure to EB-treated 10% sucrose solution (0.2 g L−1) in susceptible (SS), resistant (RR), and reciprocal F1 populations at one and three days of age. Mortality was assessed at 24 and 48 h. At 24 h, SS mortality was 100% at both ages, whereas pooled RR mortality was 70% and 65% in one- and three-day-old adults, respectively. Reciprocal F1 mortality ranged from 85–95%. Fisher’s exact tests showed lower RR mortality than SS at both ages (P = 0.020 and 0.008) and after pooling ages and sexes (P < 0.001). By 48 h, mortality reached 100% in all groups except three-day-old RR females (90%). Resistance expression was most clearly detected during the first 24 h.