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.
Highlights
The productivity of wheat, Triticum aestivum L. is strongly influenced by the attack of insect pests
At 3 days after spray application, it could be noted that there was a difference in the S. graminum population among the nozzle, adjuvants and application rates
The results found here with imidacloprid approached those found by Elzen (2001), who provided eggs of Helicoverpa zea (Boddie, 1850) (Lepidoptera: Noctuidae) previously treated with this insecticide to males and females of O. insidiosus, and observed a reduction in the survival of this predator, averaging 52.2 and 37.3% reduction, respectively
Summary
The productivity of wheat, Triticum aestivum L. is strongly influenced by the attack of insect pests. The chemical control is predominantly used in the management of aphids as the green aphid of cereals, or wheat aphid (Schizaphis graminum Rondani, 1852), which can cause up to 50% of direct (sap suction) and indirect (fungal growth on honeydew) yield losses (Kindler et al, 2002; Van-Emden and Harrington, 2007; Royer et al, 2015) This aphid is widely distributed in the wheat production regions of the world (Blackman and Eastop, 2000). Wheat production is very dependent on the use of insecticides, which increases production costs and generates several social and environmental problems (Salvadori, 1999) Chemical control of this insect pest is recommended when 10% of plants are infested during the vegetative phase or when it exceeds ten aphids per spike, until the mass phase of the wheat grain (Silva et al, 1996)
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