Relationship between enzyme activity and resistance to insecticides in the tested field strains of Aphis gossypii (Hemipetra : Aphididae)‎

الملخص EN

The cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae) is phloem feeders, often found on the abaxial leaf surface and excrete the excess material obtained from the phloem as honeydew and in high numbers can cause leaf curling and its honeydew can create a shine on the leaves.

Resistance to several insecticides belonging to different groups in the six field strains of the cotton aphid, A.

gossypii collected from Behera, Dakahlia, Menofia, Skarkia, Gharbia and Beni-Suif Governorates in 2010 cotton season was investigated using slide-dipping method.

The insecticides used in this study belong to organophosphates, carbamates, pyrethorids and neonicotinoids.

The results indicated that the field strains exhibited high levels of resistance to the organophosphates fenitrothion, prothiofos, pirimiphos methyl and malathion (RR=9.6-49-fold), the carbamates pirimicarb and carbosulfan (RR= 14.8-53.4-fold), pyrethroids lambdacyhalothrin, alpha-cypermethrin, fenpropathrin, and esfenvalerate (RR=11.9-44.7-fold) and the neonicotinoids imidacloprid, acetamiprid and thiamethoxam (RR = 2.1-8.2- fold), except for thiamethoxam in Menofia and Dakahlia (11.5 and 14.0-fold, respectively).

Enzyme activities of esterases and acetylcholinesterase (AChE) were studied in six field strains of A.

gossypii.

The results indicated that field strains exhibited higher levels of α - and β - esterase activities and lower AChE activity than those achieved in the susceptible strain.

These results indicated that esterases may appear to play insecticide resistance belonging to different groups, while AChE may also appear to play a role in organophosphates and carbamates.

However, positive correlation between esterase activity and insecticide resistance or negative correlation between AChE and organophosphate or carbamate resistance but not significant was observed at 1% or 5% accuracy level.

Therefore, esterase and AChE activities may not relate to insecticides resistance.