ABSTRACT

A strain of beet armyworm larvae, collected in May, 1991, from peppers near Donna, TX, in the LRGV, was selected for resistance for nine generations to 11 insecticides in three classes. An LD₅₀ of 20 µg/larva was used as the resistance threshold for each insecticide each generation. The strain was resistant to fenvalerate each generation. It was resistant to permethrin, methyl parathion and methomyl in certain generations, but was susceptible in other generations. Susceptibility of the strain was shown by 33%, 100%, 89%, 100%, 0%, 67%. 33%, 50% and 0 % of insecticides tested from generations one through nine, respectively. Multiple resistance was exhibited in generations one, five, six and eight.