Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/16/1996
Publication Date: N/A
Interpretive Summary: The Russian wheat aphid, Diuraphis noxia (Mordvilko), is a recent introduction into the United States and Canada. The estimated economic losses from the US cereal industry due to D. noxia from 1987 through 1993 have averaged over $127 million per year, with a cumulative total of nearly $900 million. Modified cultural practices and control of volunteer wheat and barley can be important in minimizing D. noxia infestations; however, chemical control is the primary method used, and the cost to the environment is of growing concern. CGA 215944 and Gaucho are newly developed insecticides with primary activity on sucking insects and will likely become available for use against aphids in cereal agroecosystems. At low concentration these insecticides have been reported to have antifeedant effects on aphids and, excluding host mortality, are touted as being innocuous to natural enemies. We assessed quantitatively, by using electronic feeding monitors, the systematic effects of low concentrations of CGA 215944 and Gaucho on D. noxia feeding behavior and found that only CGA 215944 had an antifeedant effect on aphids, and there were no substantial carryover effects from either insecticide on the tritrophic relationship between host plant, D. noxia, and aphid parasitoid, Diaeretiella rapae McIntosh.
Technical Abstract: The effect of low concentrations of systematically applied aphicides CGA 215944 and Gaucho (imidacloprid) on the feeding behavior of the Russian wheat aphid, Diuraphis noxia (Mordvilko), on wheat was evaluated using electronic feeding monitors. Aphids began surviving 15 days after treatment with CGA 215944 (soil drench, 10 g ai/liter) and 45 days after planting on plants grown from seed dressed with Gaucho (1 fluid oz/cwt). Following these periods of acute toxicity, CGA 215944 exhibited antifeedant effects on D. noxia that were expressed by changes in the frequency and duration of different feeding behaviors. Aphids on plants treated with CGA 215944 spent significantly more time in nonprobing activities and had a much higher frequency of leaf penetration spikes followed by significantly shorter periods of phloem ingestion. Immediately after the period of acute aphid toxicity, there were no substantial carryover effects from CGA 215944 or Gaucho on the tritrophic relationship between host plant, D. noxia, and Diaeretiella rapae McIntosh.