New approaches for controlling the black cutworm Agrotis ipsilon (Hufn.) (Lepidoptera : Noctuidae)

Three commercial products namely MVP11 (delta endotoxin of Bacillus thuringiensis), Match, an I.G.R. (Lufenuron) and Marshal (chemical insecticide) were tested against 2 nd and 4 th instar larvae ofAgrotis ipsilon. Larvae of 2 nd instar were allowed to feed on caster-bean leaves dipped for one minute at each concentration used of the three tested materials. Larvae of 4 th instar were allowed to feed on a toxicant bait. The LCso values 72 h. post treatment with MVP11 were 355. 8 and 480.2 ppm for 2 nd and 4 th instar larvae while, those of Match treatments were 98.7 and 120.1 ppm, respectively. In the case of the chemical insecticide Marshal, the LC 50 values which were estimated 24 h. post treatments were 99.7 and 111.6 ppm, respectively. Delayed effect of the three tested materials were also studied among the surviving treated larvae. Occurrence of malformations for dif ferent stages could be detected within different concentrations of MVP11 and Match treatments while, it didn't occur at all concentrations of chemical insecticide (Marshal). This indicated that, the effect of exposure to different concentrations of MVP1, and Match was extended from treated larvae to the resultant pupae and adults. Larvae which could tolerate exposure to MVP11 or Match concentrations and proceeded their development till successful pupation may fail to emerge as adults. Although, the lower concentrations of Match were less effective than those of MVP11, the latent inhibitory action on different stages exclusion gave an evidence of higher potential for Match than that for MVP11. At concentrations of 100, 200, 400, 800 and 1600 p.p.m. of MVP11 treatment the final effect on different stages were 55.56, 68.89, 76.67, 83.34 and 93.33% for 2 nd instar and 48.88, 61.12, 72.22, 79. 9 9 and 90.00% for 4 th instar larvae. The corresponding values of 2 nd and 4 th instar larvae treated with Match were 57.77, 69.99, 77.77, 86.66 and 96.67% and 51.1, 63.32, 71.11, 79. 99 and 92.22% at concentrations of 50, 100, 150, 200 and 250 p.p.m., respectively. Regarding to final percent mortality of different stages, Marshal insecticide treatment was the most effective, resulting in 60.00, 73.33, 86.67, 100 and 100 for the 2 nd instar and 56.67, 70.00, 83.33, 96.67 and 100% for the 4th instar at concentrations of 50, 100, 150, 200 and 250 ppm, respectively.