Abstract
The assessment of acute toxicity to insect natural enemies is very important for insecticide selection used within integrated pest management (IPM). The acute toxicity of abamectin and imidacloprid against Encarsia formosa, a parasitoid of Bemisia tabaci, was investigated. Abamectin had a high toxicity risk to E. formosa, while imidacloprid showed a medium toxicity risk. When treated with the lethal concentration 30 (LC30) of abamectin, the dwelling time of E. formosa in B. tabaci infested-plant-area (IPA) was significantly lower than in non-infested plant areas (non-IPA). In addition, the frequency of E. formosa entering into the two areas was not significantly different in the LC10 and LC30 treatments. Within the IPA, LC10, and LC30 treatments decreased the dwelling time and entering frequency of parasitoid significantly. For imidacloprid treatments, E. formosa stayed a longer time in the non-IPA than in the IPA when treated with LC30. The frequency of E. formosa entering into the two areas was only slightly different in the LC1, LC10, and LC30 treatments. Within the IPA, LC10 and LC30 treatments were significantly decreased in the dwelling time and the entering frequency of E. formosa. The results indicate that abamectin and imidacloprid have high or medium acute toxicity against E. formosa and a negative sublethal effect on its searching behaviour.
Highlights
Pesticide application still remains the main approach for B. tabaci management but the overuse of chemical pesticides has resulted in strong chemical resistance outbreaks for this whitefly pest [7,8]
The evaluation of the acute toxicity can provide partial assessment concerning the potential effects of pesticides to the exposed non-target organisms [21,22], while sublethal effects of insecticides on natural enemies may cause a decrease in their efficiency as biological control agents
Results revealed that the lethal concentration 30 (LC30) and LC50 value of both insecticides to E. formosa adults increased with the longevity of the parasitoid, indicating the relatively higher chemical tolerance of older adult wasps than the younger adults (Tables 2 and 3)
Summary
The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a global agricultural pest [1,2].This whitefly pest causes serious damage to hundreds of crops directly by sucking phloem sap, and indirectly by causing sooty mould growth via honeydew secretion and, most importantly, by the transmission of numerous plant viruses [3,4,5,6].Pesticide application still remains the main approach for B. tabaci management but the overuse of chemical pesticides has resulted in strong chemical resistance outbreaks for this whitefly pest [7,8].integrated pest management (IPM) is considered a more sustainable approach for the control of B. tabaci and, as a key part of IPM, biological control with parasitoids plays an important role in sustainable insect pest control [9]. The evaluation of the acute toxicity (i.e., lethal effect) can provide partial assessment concerning the potential effects of pesticides to the exposed non-target organisms [21,22], while sublethal effects of insecticides on natural enemies may cause a decrease in their efficiency as biological control agents. To completely assess the effects of an insecticide on a natural enemy, the risk-assessment should include acute toxicity as well as sub-lethal and chronic effects [23,24] Based on these findings, the selection of appropriate insecticides that have a less negative impact on a given specific natural enemy is critical in the development and success of IPM of invertebrate pests [25]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
