Side effects of some herbal insecticides on Bemisia tabaci and Encarsia formosa

Encarsia formosa is one of the natural enemies of whiteflies. Chemical control of pests often results in exposure of helpful insects including E. formosa. Plant extracts may provide an alternative method to applied pesticides. In this research the mortality effects of two plant extracts, Allium sativum and Calotropis procera, were assessed in compare to neemarin and pymetrozine, on pupa and adults of E. formosa. Also, repellency effects of the studied treatments were evaluated on adults of silverleaf whitefly, 3 and 24 hours after treatment. The most toxic compound for pupa was azadirachtin which caused 100% mortality. This value was followed by extracts of C. procera and A. sativum. The mortality caused by pymetrozine did not differ from control significantly. Toxicity of the treatments for the adults was as follows azadirachtin > C. procera > pymetrozine > A. sativum. Also, extract of C. procera in both period times and azadirachtin three hours after application had significant repellency effects for silverleaf whitefly. According to the results, azadirachtin application is harmful for both tested stages of E. formosa. If similar results are obtained from field trials, its usage requires necessary precautions. The findings of this study can be useful for improving of IPM programs.