Emamectin benzoate resistance risk assessment in Dysdercus koenigii: Cross-resistance and inheritance patterns

Abstract

Dysdercus koenigii (Fabricius) is an economic pest in the cotton agro-ecosystem of Pakistan. Cross-resistance and inheritance patterns of emamectin benzoate resistance were explored in D. koenigii populations from Southern Punjab, Pakistan. After seven selection cycles with emamectin benzoate, a D. koenigii field population gained 48342-fold resistance to emamectin benzoate. The dominance value of emamectin benzoate resistance was 0.95 for both F1 and F1‡, suggesting complete dominant resistance. Backcrosses of hybrids with susceptible parents predicted polygenic resistance. Realized heritability of emamectin benzoate resistance was 0.59. When mean slope = 2.03 and h2 = 0.59, 4.8–1.6 generations were projected for a 10-fold increase in lethal concentration 50 (LC50) values at 45–95% mortality. Cross-resistance analyses revealed extremely high (411–69592-fold) cross-resistance to all tested insecticides when compared with the susceptible reference strain and extremely low cross-resistance to acetamiprid (resistance ratio (RR) = 2.6), low cross-resistance to imidacloprid (RR = 20). High cross-resistance to lambda-cyhalothrin (RR = 85) and extremely high cross-resistance to deltamethrin (RR = 2540) in emamectin benzoate-selected D. koenigii were also noted when compared to the field population. It can be concluded that the emamectin benzoate-selected strain revealed autosomal, completely dominant, polygenic resistance and high to extremely high cross-resistance to lambda-cyhalothrin and deltamethrin. These results will assist in improving management of D. koenigii.