Effects of the aphicides 'Gaucho' and CGA-215944 on feeding behavior and tritrophic interactions of Russian wheat aphids

The effect of low concentrations of the systemic aphicides CGA 215944 and Gaucho registered (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 treated 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, 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.