Toxicity and persistence of selected neonicotinoid insecticides on cowpea aphid, Aphis craccivora Koch (Homoptera: Aphididae)

Abstract

Field strain of cowpea aphid, Aphis craccivora Koch, was treated by selected neonicotinoid insecticides to evaluate their toxicity and persistence against this pest in Assiut governorate, Egypt. Under faba bean field conditions, acetamiprid, imidacloprid, thiamethoxam and dinotefuran registered significantly high percent reduction of the pest at one, seven, fifteen and 21 post treatment. The residual effects of these insecticides showed that the LT₅₀ for acetamiprid, imidacloprid, thiamethoxam and dinotefuran were 5.8, 6.2, 6.95 and 4.2 days, respectively. The application of these insecticides on the cowpea aphid under field conditions induced yield increases. The toxicity of these neonicotinide insecticides were tested against field strain of cowpea aphids using leaf-dib bioassay under field and laboratory conditions. The toxicity index showed that thiamethoxam, acetamiprid and imidacloprid have the highest aphicidal activity, with LC_50s 0.60, 0.71 and 1.16 mg/L, respectively, while dinotefuran was the least toxic one with LC₅₀ 23.41 mg/L. Results of this study indicated that neonicotinoid insecticides were highly effective against cowpea aphid under field and laboratory conditions.

Keywords:

• pest control
• residual effect
• leaf-dipping method
• bioassay
• aphid

Acknowledgements

The author wishes to thank the Plant Protection Department, Faculty of Agriculture, Assiut University Egypt, for continuous supporting. Many thanks are also extended to Prof. Dr. Bruno Lapied, head of the laboratory, RCIM (Receptors and Membrane Ion Channels) UPRES EA 2647 USC INRA 1330, Faculty of Science at Angers University, France, for allowing me to use Graph Pad Prism 5^TM software (San Diego, CA).