Evaluating Four Bioassay Techniques for Insecticide Resistance Monitoring in Helicoverpa armigera (Lepidoptera: Noctuidae)

Abstract

Laboratory studies were performed on Helicoverpa armigera strain collected from Werer Agricultural Research Center cotton fields to investigate resistance to the field rates of profenofos, endosulfan and lambdacyhalothrin using adult vial, topical application, square dip and larval immersion techniques. It was found that LD50 values of endosulfan, profenofos and lambdacyhalothrin in the third instar topical bioassay were 29.84, 4.068 and 0.18 mg/g body weight, respectively. In the square dip test profenofos (Calofos) resulted in 100% kill at two-times lower dose (1.25 x 10^-3 g a.i/ml) and 86.67% larval deaths were observed at four-times lower dose. Endosulfan (Ethiosulfan) gave 99.33% only at the field rate (5.25 x 10^-3 g a.i/ml). Lambdacyhalothrin (Karate) was observed to yield 99.33% larval death at eight-times lower dose (6.25 x 10^-5 g a.i/ml) than the field rate. In larval immersion experiment lambdacyhalothrin and profenofos gave 98.33 and 99.33% kills at eight-time lower dose, respectively, while endosulfan expressed 96.67% efficacy only at the field rate. LC50, and LC90 in adult vial test for endosulfan were found to be 1.333 and 3.099 mg/ml, respectively. However, the observed high mortality (> 25%) in control treatments warranted reevaluation of adult vial technique. Square dip technique was found easy and economical.