STUDIES ON SOME APHID PARASITOIDS IN NORTH AFRICA

Abstract

Wheat is a major cereal crop. Aphids are the serious insect pests attacking wheat plants, Aphid parasitoids are one of the groups whose utilization in biological control. Aphidius colemani Viereck (Hymenoptera: Aphidiidae) is one of the most important primary parasitoid species of aphids. Survey of cereal aphid species and their parasitoids in wheat fields was carried out at Kafr El-Zayat and El-Shuhada, Gharbia and Menofia Governorates, for two successive growing seasons 2000/0 I and 200 l/02.Highest number of individuals of the parasitoid was recorded during the second and third weeks of February and then during March in the two sites and in the two seasons. Total percentage of A. colemani among the recorded primary parasitoid species on cereal aphids reached 14.2 and 13.6% at Kafr El-Zayat and 21.7 and 12.5% at El-Shuhada in the two seasons, respectively. The biology studied of life table using R. padi and S. graminum on wheat, and barley, also results of life table using R. padi and S. graminum on the wheat cultivars coded 3, 5 and 8, and results of life table using the parasitoid A. colemani on R. padi and S. graminum on the wheat and barley. The three wheat cultivars coded 3, 5 and 8 were tested in this experiment to study host plant resistance phenomenon in both cereal aphid species; R padi and S. graminum when the two species were exposed separately to A. colemani. Biology of different . stages of the parasitoid A. colemani on both R. padi and S. graminum on wheat and barley were daily dissection of parasitized aphids at different intervals (6 hours) was the technique used in this experiment to estimate the durations of different stages of the parasitoid. Emergence (adult stage) took place at any time of the day, mating always took place during the first day of emergence. Fecundity of the parasitoid female of A. colemani was determined by counting the total number of eggs deposited internally inside the offered individuals of the hosts by dissection. Adult longevity was determined for both sexes under the abovementioned laboratory conditions using different diet regimes of honey, unfed and on distilled water. The efficacy of the parasitoid species A. colemani was evaluated under semi-field conditions by releasing in cages. Host Preference for A. colemani on R. padi, S. graminum and R. maidis.