Occurrence and parasitism of aphids (Hemiptera: Aphididae) on cultivars of irrigated oat (Avena spp.) in S？o Carlos, Brazil

the interactions between aphids and their hymenopteran parasitoids on irrigated oats as well as the response of different cultivars of cereals regarding the resistance to these aphids and the influence on the host/parasitoid relationships were studied during two years in s？o carlos, brazil. rhopalosiphum padi (l.) was the predominant aphid observed throughout the study, while the other species were rarely found. five species of parasitic hymenoptera were found: three primary parasitoids, lysiphlebus testaceipes (cresson), aphidius colemani (viereck) and diaeretiella rapae (m'intosh) and two hyperparasitoids, syrphophagus aphidivorus (myer) and alloxysta brassicae (ashmead). the upf 86081 cultivar presented significant results regarding lower rhopalosiphum padi contamination and higher aphid parasitism rates than those observed on some other cultivars. no significant effect on the percentage variation of parasitoid emergence on the mummified aphids was observed throughout this study.