CROSS RESISTANCE PATTERN FOR EMAMECTIN BENZOATE an‎d SYNTHETIC PYRETHROIDS IN DIAMONDBACK MOTH, PLUTELLA XYLOSTELLA (L.) (LEPIDOPTERA: PLUTELLIDAE

Three pyrethroids (deltamethrin, bifenthrin and ג-cyhalothrin) and four new chemistry insecticides were tested against second instar larvae of Plutellaxylostellaunderlaboratory condition. Based on their LC50values, deltamethrin was most toxic than ג-cyhalothrin and bifenthrinand among new chemistryinsecticides, emamectin benzoate was the most toxic followed by acetamiprid, diafenthiuron and imidacloprid. Selection of two subpopulations for five generations with gradual toxic exposures of deltamethrin and emamectin showed decrease in survival rate. However, there wasno drastic increase in LC50values for both selected subpopulations than that of unselected subpopulation. Such high cross-resistance between emamectin benzoatewith deltamethrin and ג-cyhalothrinsuggest their wise use against this important insect pest. Rotational use of insecticides with different mode of action against P. xylostellamighthelp avoiding development of resistance.