Abstract :
The susceptibility of the 4PthP larval instar of the laboratory strain of Helicoverpa armigera (Hubner) to Abamectin efficiency was evaluated by using different techniques; i.e., dipping, surface film and immersion methods of technique. Abamectin was bio-assayed after 24, 48 72 and 96 hours from the treatment for each technique. The obtained results revealed that the order of the efficiency of the product used against the tested larvae was the same at both LCR50R and LCR90 RvaluesR. RThe highest efficiency of Abamectin for dipping technique was attained 96 hours. The corresponding LCR50R and LCR90R values were 51.76 and 93.78 ppm, respectively, while, the lowest efficacy of the product was pronounced at 24 hours, the corresponding LC50R Rand LCR90R values were 93.51 and 236.71ppm, respectively. Whereas the biological activity of the compound against the 4PthP larval instar fed on treated leaves for 48 and 72 hr. occupied middle situation among its efficiency at 24 and 96 hr. The corresponding LCR50 Rand LCR90R values of the tested biocide after 48 hrs., were 81.52 and 214.46 ppm. On the other hand these values after 72 hr. of feeding were 69.92 and 119.15 ppm, respectively. The susceptibility rates of the 4PthP larval instar to abamedtin toxicity at LCR50R and LCR90 Rvalues wereR R185.93 421.34, 135.34 378.25 , 114.66 211.64 and 95.58 124.29 ppm for surface film technique and 114.73 257.19 91.32 188.65 81.56 151.15 and 60.58 101.19 ppm for immersion method respectively. On the other hand, the susceptibility index as well as the potency levels at both LCR50R and LCR90 Rvalues increased with increasing the period determination .The latent effects of Abamectin on the pupation as well as the adult emergence was determined. The corresponding EC50 and ECR90R values associated to quantal scoring of pupation due to dipping surface film and immersion bioassay were 2.63 120.51 , 82.02 198.12 and 45.45 137.42 ppm respectively. Whereas the corresponding ICR50R and ICR90R values for inhibition of the adult emergence were 20.14 91.02, 74.12 136.22 and 43.22 101.32 ppm respectively.
