Application technology of imidacloprid in wheat: Effects on Schizaphis graminum management and natural enemies

Abstract

Wheat production is dependent on costly insecticides that generate social and environmental issues. The growing demand for a rate reduction of spray applications and increased spray efficiency make essential the research for more adequate crop management. Therefore, this study aimed to evaluate technologies of imidacloprid application on wheat aphid, Schizaphis graminum and its natural enemies, Chrysoperla externa and Orius insidiosus. A set of experiments were performed to evaluate the effectiveness of S. graminum control and the toxicity to natural enemies using imidacloprid plus adjuvants sprayed with different nozzles and application rates. Improved S. graminum control was observed in the association between the adjuvant lauryl ether sodium sulfate and the hollow cone nozzle for both application rates (75 and 150 L ha-1), and the adjuvant copolymer of polyester + silicone + d-limonene with the asymmetric twin flat-fan nozzle at a low rate (75 L ha-1), since these treatments eliminate the wheat aphid after the fifth day of treatment application. The reduction of spray volume to wheat aphid control is possible with no loss of insecticide effectiveness. Imidacloprid associated with any one of the adjuvants tested is harmful to C. externa and O. insidiosus, even at the fifth day after application the insecticide continues being harmful to the natural enemies, regardless of the technology used.   Key words: Triticum aestivum, Schizaphis graminum, ecological disturbance, insecticide impacts, natural control, neonicotinoid.