Cereal Aphid Species (Homoptera : Aphididae) Infesting Wheat Plants and their Aphidophagous Insects at El-Khattara District, Sharkia Governorate, Egypt

Abstract

Studies on cereal aphids infesting wheat plants and their aphidophagous insects were carried out in newly reclaimed sandy area at El-Khattara district, Sharkia Governorate, Egypt during 2015-2016 and 2016-2017 growing seasons.The obtained results are summarized as follows:Four aphid species, i.e., Shizaphis graminum (Rondani), Rhopalosiphum maidis (Fitch), Rhopalosiphum padi (Linnaeus) and Macrosiphum avenae (Fabricius) were found infested wheat plants.Cereal aphids infested wheat plants from the first week of January till the last week of April. The highest populations of aphids were recorded in the first week of March and in the second week of April with counts of 711 and 1503 individuals/ sample in the first and second seasons, respectively.Six predaceous insect species belonging to four orders and five families were surveyed associated with aphid species infesting wheat plants. Coleopterous species were the most dominant, followed by the neuropterous ones, with general relative densities of 41.70 and 21.10 % of the total recorded predators, successively. Among all recorded predaceous species, Chrysoperla carnea (Stephens) , Coccinella undecimpunctat L., and Coccinella septempunctata L., were the most dominant species, comprised 21.10, 15.68 and 15.26 % of the total count of the predators, respectively. The total recorded predators showed that means of 1:61.62 and 1:118.73 predators: prey ratios in the first and second seasons, respectively.Five species of hymenopterous parasitoids were emerged from mummified individuals of cereal aphids, namely, Diaeretiella  rapae (M’Intosh), Aphidius colemani Viereck, Aphidius matricariae Haliday, Ephedrus sp. and Praon sp. The most dominant parasitoids were D. rapae and A. colemani with general relative densities of 35.32 and 27.12% respectively. The fluctuations of the  total percentages of parasitism indicated three peaks in the first season and two ones in the second season. The mean percentage of parasitism during the first season was relatively high (6.41%) in comparison with that in the second one (3.60%).The correlation between cereal aphids populations and percentages of parasitism in both seasons were positive high significant