Hymenopterous parasitoids associated with cereal aphids in wheat fields at Assiut

ABSTRACT

The present study was carried out in Assiut area to investigate the relationship between cereal aphids and their associated parasitoids on wheat plants during two successive seasons, 2011 and 2012. The results indicated that of 48,000 mummified aphids collected from wheat plants in two seasons, 89.69% adult parasitoids were emerged. Ten parasitoid species belonging to five families of order hymenoptera were identified. The primary parasitoid species were recorded, Aphidius colemani Vereck, A. matricariae Haliday, Diaeretiella rapae [Mclntosh], ffptiedrus plagjfator[Ness], Praon necans Mackauer and Trioxyssy., in addition the secondary parasitoids were, AUoxysta Australia [AsbmQandA], Dendrocerus carpenter [Cuitis], Chalclds sp.,and Aphidencyrtus sp. Data show that, Diaeretiella rapae was the most dominant and abundant primary parasitoid species represented 87.99% and 64.35% during 2011 and 2012 seasons, respectively. In spite of aphids, five aphid species namely, Scbhaphis grawinumfiwfaw, Rbopaloslphum pad! L, R. maldls [Fitch.], Sitobion avenae [Fab.] and Metopolophium dlrbodum [Walker] were found attacking wheat plants in Assiut region. Rbopaloslpbum padl and Schizaphls gramlnum were the most dominant and abundant cereal aphids on wheat plants represented [55.55 and 54.41%] and [40.68 and 43.11%] in both two species during 2011 and 2012 seasons, respectively. The maximum population level of cereal aphids was recorded during the 1[st] wk of March [529.0 and 729.0] during the two seasons, respectively. The parasitoids appeared early in the season in relatively low population density but its population fluctuated in high density during the 2nd wk of March [408.0 and 335.6] in 2011 and 2012 seasons, respectively, coincided with the collapse of aphids from wheat field. This work indicated that wheat fields are rich in aphid parasitoid species which of course play a significant role in suppressing aphid infestations