Abstract
BACKGROUND Imidacloprid, a neonicotinoid insecticide, is widely sprayed alone or mixed with other insecticides againstDysdercus koenigii, a potential pest of cotton in Pakistan. Recently, resistance to imidacloprid in field populations ofD. koenigiihas developed because of its overuse. Herein, we have investigated inheritance of imidacloprid resistance inD. koenigiiand its cross-resistance to other insecticides. RESULTS The imidacloprid-selected population had a 91 421-fold increase in resistance to imidacloprid after six generations. Overlapping 95% fiducial limits of LC(50s)of the F-1(Imida-Sel male x Sus-ST female) and F-1(dagger)(Imida-Sel female x Sus-ST male) suggested an autosomal and incomplete dominant resistance to imidacloprid (D-LC= 0.84 for F(1)and 0.86 for F-1(dagger)). Reciprocal backcrosses of the F(1)and F(1)(dagger)with Sus-ST predicted a polygenic inheritance. Realized heritability of imidacloprid resistance was 0.38. When mean slope = 1.74 andh(2)= 0.38, then 3-13 generations would be required for a ten-fold increase in LC(50s)at 90-20% intensity of selection. Very high cross-resistance to emamectin benzoate (143-fold), deltamethrin (1675-fold) and lambda-cyhalothrin (140-fold), and moderate cross-resistance to acetamiprid (37-fold) in the imidacloprid-selected strain compared to the field population were observed. CONCLUSION Imidacloprid resistance developed very quickly under continuous selection pressure in the laboratory. These factors might lead to an increasing likelihood of resistance development in field populations, if imidacloprid is used continuously without insecticide rotation for prolonged periods. The present results would be supportive for better management ofD. koenigiiby devising an effective resistance management strategy. (c) 2020 Society of Chemical Industry