Short-term effect of thiamethoxam through different exposure routes on Aphis gossypii (Hemiptera: Aphididae) and its predator, Orius albidipennis (Hemiptera: Anthocoridae)

Abstract

ABSTRACTWe assessed the short-term effect of different exposure routes of the neonicotinoid thiamethoxam (TMX) on the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), and one of its predators, Orius albidipennis (Rueter) (Hemiptera: Anthocoridae), to determine the feasibility of simultaneous use of the predator and TMX in cotton aphid control programmes. TMX was applied against A. gossypii and the predator at the maximum field recommended concentration (MFRC), ½ MFRC, and ¼ MFRC via leaf-dip, aphid-dip, and soil application treatments. It was extremely toxic to A. gossypii (64.96%–91.9% mortality in 1st instar nymphs and 51.33%–80.48% mortality in adults, 72 h after treatment) regardless of the concentrations used or the exposure treatment method. The insecticide exhibited very low lethality (<12.45% mortality) to 1st instar O. albidipennis nymphs after being absorbed systemically from the soil through the cucumber plant’s roots. The other two exposure routes, however, were extremely toxic to the predator, causing more than 67% mortality after 72 h exposure. The mortality of both aphid and predator increased over time in all three bioassay methods. These results demonstrated that the choice of TMX application method had no noticeable effect on its efficacy against cotton aphid but was a critical consideration in the conservation of its natural enemy, O. albidipennis, suggesting that soil application of TMX is potentially compatible with O. albidipennis. However, for definitive confirmation of this, the sublethal effects of the compound on the predator need to be studied, along with long-term assays under laboratory and field conditions.