Assessing the resistance risk to emamectin benzoate in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae): selection, cross-resistance dynamics and estimates of realized heritability

Abstract

• 280.15-fold resistance was detected in Phenacoccus solenopsis to emamectin benzoate. • CR to abamectin and profenofos was 0.28-1.65-fold, and 0.12-0.29-fold, respectively. • CR to cypermethrin ranged from 6.02-11.29-fold. • h 2 of resistance to emamectin benzoate was 0.24 from G 3 to G 19. Emamectin benzoate, a non-systemic, translaminar, and broad spectrum insecticide, is excessively used in cotton. It kills the pest by suppressing the muscle contraction. Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is one of the major sap sucking pests of cotton in many countries and has been shown resistance to various insecticides. In this study, we have continuously selected P. solenopsis with emamectin benzoate in the laboratory from G 3 to G 18 to determine the resistance development and resistance risk to emamectin benzoate and also to evaluate the dynamics of cross-resistance (CR) development with three other insecticides. After continuing selection of P. solenopsis for 16 generations with emamectin benzoate, the emamectin selected strain (Ema-SEL) developed a 280.15-fold resistance when tested at G 19 . Ema-SEL strain showed no CR to abamectin (0.28-1.65-fold), and profenofos (0.12-0.29-fold), but a very low to low CR to cypermethrin (6.02-11.29-fold). Abamectin was negatively cross-resistant with emamectin benzoate in Ema-SEL strain at G 13 , G 15 and G 19 while profenofos also exhibited similar results at G 13 , G 15 , G 17 and G 19 . Realized heritability ( h 2 ) of resistance to emamectin benzoate was 0.24 from G 3 to G 19 . The results of projected rate of resistance development showed that if h 2 = 0.24, 0.34, and 0.44 at slope = 1.08, then 2.03, 1.43, and 1.11 generations, respectively are required for ten-fold increase in LC 50 at 95% selection intensity. Results of the present study suggested that P. solenopsis has the ability to develop resistance to emamectin benzoate but it can be managed by the alternate use of other insecticides including abamectin, profenofos and cypermethrin due to lack of/or very low to low CR with these insecticides.