Studies on some Parasitoids of the Cowpea Aphis Aphis craccivora Koch (Homoptera: Aphididae) in Egypt.

Survey and population density of the aphid species Aphis craccivora (Koch) infesting broad bean plants and its parasitoids were studied at Zagazig district during the two successive seasons 2006-07 and 2007-08. Two primary parasitoids, Diaeretiella rapae (M'Intosh), Ephedrus sp. (Aphidiidae), and a hyperparasitoid, Aphidencyrtus sp. (Encyrtidae) were recorded. Highest rates of parasitism 12.73% were recorded in the 4th week of January 2006-07 and 11.09% in the 2nd week of February 2007-08. Seasonal means of parasitism rates of the primary parasitoids D. rapae and Ephedrus sp. were 8.17 and 6.45% during the two seasons, respectively. Total developmental period of the two parasitoids was investigated at three temperatures (10, 15 and 28 °C). The duration of the two parasitoids was longest at 10 °C. Generally, developmental periods of different stages of the parasitoids shortened as the temperature increased from 10 to 28 °C. Total developmental periods of the two parasitoids ranged between 11.17-27.16 and 12.38-30.48 days for D. rapae and Ephedrus sp., respectively. Sex ratios were 1:1.1 and 1:1.07 (m:f) for D. rapae and Ephedrus sp., respectively. Temperature and relative humidity played an important role in the population changes of A. craccivora, D. rapae and Ephedrus sp. Temperature showed a highly significant effect on the population density of Ephedrus sp. in both seasons. The maximum temperature and the minimum relative humidity had a positive significant effects on the population density of D. rapae at both seasons. [ABSTRACT FROM AUTHOR]