RESISTANCE LEVELS EVALUATION OF CERTAIN FIELD ENVIRONMENTAL STRAINS OF APHIS CRACCIVORA TO SOME INSECTICIDES

Abstract

The present investigation aimed to evaluate the susceptibility of adults of cowpea aphid, Aphis cvaccivora (koche,) populations collected from four Egyptian Governorates, Behira, Gharbia, Sharkia and Beni-suief. in two successive years (2008-2009) to organophasphorus compounds (pirimiphos-methyl & chloryrifos methyl) and from carbamate compounds, (Carbosulfan & Pirimicarb), the neonicotionoid compounds (imidacloprid and thiamethoxame), and diafenthiuron from thiourea insecticides . Obtained results clearly indicated a great effect of the neonicotionoid compounds with LC50’s 0.14ppm, 0.94ppm for imidacloprid and thiamethoxame, respectively, followed by carbamate compound pirimicarbe which was more potent than carbosulfan with LC50’s 1.32 ppm and 1.47 ppm respectively, then thiourea compound diafenthiuron with LC50’s 1.66 ppm and finally the organophosphorous group; pirimiphos – methyl (LC50 6.54 ppm) followed by chlorpyrifos – methyl (LC50 8.56 ppm) for susceptible strain. The neonicotionoid compounds proved to be the most effective compounds than other investigated conventional insecticides, in all of the Governorates population. Also Beny-suif population was the most resistant one among all tested aphid populations. Laboratory selection pressure was applied for Behira strain to build up resistance toward imidacloprid insecticide. The level of selection pressure was carried out using LC25 and LC50 values of the compound. After 21 generations, the level of resistance to imidaclopride was 150.09 fold relatively to susceptible strain and 37.52 fold relatively to parent field strain. There was no cross resistance between imidaclopride R strain and pirimiphos-methyl and diafenthiuron while highly cross resistance was observed between imidacloprid R strain and pyrethroid compound lambada- cyhalothrin which recorded 121.8 fold. The protein fraction patterns, AChE and phosphatases activity in investigated field strains comparing with susceptible strain were evaluated the data revealed that such parameters may be taken as marker to the differences in susceptibility of strains to insecticides. Key words: Aphis crassivora, insecticides, resistance, protein, phosphatases and AChE.