Lethal and sublethal effects of clothianidin, imidacloprid and sulfoxaflor on the wheat aphid, Schizaphis graminum (Hemiptera: Aphididae) and its coccinellid predator, Coccinella septempunctata

Abstract

The use of pesticides for greenbug, Schizaphis graminum in wheat not only can manage the pest population but also can influence its predator, Coccinella septempunctata. Acute and chronic effects of imidacloprid, clothianidin and sulfoxaflor on S. graminum and its predator, C. septempunctata were investigated. The results showed that LC50 of imidacloprid, clothianidin and sulfoxaflor to S. graminum at 48 h was 9.80, 34.29 and 4.40 ml a.i. L−1, respectively, while LC50 of imidacloprid, clothianidin and sulfoxaflor to C. septempunctata at 48 h was 107.80, 49.52 and 379.26 ml a.i. L−1. Sulfoxaflor and clothianidin were found the most toxic to S. graminum and C. septempunctata, respectively. Tested sublethal doses (LC10 and LC30) of all insecticides had significant effects on percent repellency of both S. graminum and C. septempunctata. Sulfoxaflor and clothianidin proved the most repellent to S. graminum (67.00 ± 2.03% at LC10 and 86.20 ± 1.62% at LC30) and C. septempunctata (50.60 ± 2.81% at LC10 and 60.00 ± 3.26% at LC30), respectively. Sublethal doses also demonstrated significant and the lowest percentage reduction in feeding by C. septempunctata on S. graminum in sulfoxaflor treatment (LC10: 4.13 ± 0.61%; LC30: 5.26 ± 0.69%). Additionally, sublethal doses reduced body-weight of C. septempunctata adults emerged from its treated grubs. These results revealed that sublethal doses of sulfoxaflor, imidacloprid and clothianidin negatively affected the biological activities of S. graminum and C. septempunctata as compared to control. Hence it can be concluded that more attention should be paid towards strategic application of these chemicals as a part of an integrated pest management program for an agro-ecosystem exhibiting maximum activity of coccinelid-predators. Overall, sulfoxaflor proved more appropriate for use against S. graminum in C. septempunctata manipulated agro-ecosystem. However, C. septempunctata compatible integration-strategy for field-application of sulfoxaflor should be devised to enhance its effectiveness against S. graminum and selectivity against C. septempunctata.