17 Effect of terpenoid lactones with di- and trimethylcyclohexane systems... Pestycydy, 2005, (4), 17-23. ISSN 0208-8703 Effect of terpenoid lactones with di- and trimethylcyclohexane systems on the behaviour of green peach aphid Myzus persicae *) Katarzyna DANCEWICZ 1 , Beata GABRYŚ 1 , Aleksandra HALAREWICZ- PACAN 2 , Małgorzata GRABARCZYK 3 and Czesław WAWRZEŃCZYK 3 1 Institute of Biotechnology and Environmental Sciences, University of Zielona Góra, 21b Monte Cassino St., 65-561 Zielona Góra, Poland e-mail: K.Dancewicz@ibos.uz.zgora.pl 2 Department of Botany and Plant Ecology, Agricultural University, 32 Cybulskiego St., 50-205 Wrocław, Poland 3 Department of Chemistry, Agricultural University, 25 Norwida St., 50-375 Wrocław, Poland Abstract: Terpenoid lactones with di- and trimethylcyclohexane systems 2-iodo-4,4-dimethyl-9-oxabicyclo[4.3.0]nonan-8-one, 4,4,6-trimethyl- 9-oxabicyclo[4.3.0]nonan-2,8-dione, and 2-acetoxy-4,4,6-trimethyl-9- oxabicyclo[4.3.0]nonan-8-one delayed aphid settling for 1-2 hours. 2-Iodo-4,4- dimethyl-9-oxabicyclo[4.3.0]nonan-8-one reduced the duration of the irst probe 14-fold, fewer aphids reached phloem vessels, and phloem vessels were penetrated 1.5 hour later on lactone-treated plants compared to controls during the course of 8-hour experiments. The duration of the irst period of sustained feeding was shorter as was the mean probing time after the irst period of feeding, which may indicate the ingestive and post-ingestive mode of action of 2-iodo-4,4-dimethyl- 9-oxabicyclo[4.3.0]nonan-8-one. Keywords: antifeedant, feeding deterrent, EPG *) Presented at the IV-th International Conference on Arthropods: Chemical, Physiological and Environmental Aspects, Białka Tatrzańska, Poland, September 18-23, 2005.