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(R) (imidacloprid) on the feeding behavior of the Russian wh eat aphid, Diuraphis noxia (Mordvilko), on wheat was evaluated using e lectronic feeding monitors. Aphids began surviving 15 days after treat ment with CGA 215944 (soil drench, 10 g AI/liter) and 45 days after pl anting on plants grown from seed treated with Gaucho (1 fluid oz/cwt). Following these periods of acute toxicity, CGA 215944 exhibited antif eedant effects on D. noxia that were expressed by changes in the frequ ency and duration of different feeding behaviors. Aphids on plants tre ated with CGA 215944 spent significantly more time in nonprobing activ ities 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 carryove r effects from CGA 215944 or Gaucho on the tritrophic relationship bet ween host plant, D. noxia, and Diaeretiella rapae McIntosh.