PARASITISM PERCENTAGES ON APHIS CRACCIVORA KOCH. ON FABA BEAN AND COWPEA PLANTS IN NEWLY RECLAIMED LAND IN EGYPT

Abstract

The population densities of the cowpea aphid, Aphis craccivora Koch on faba bean and cowpea plants and its parasitoids were studied at El-Khattara district, Sharkia Governorate, Egypt in 2010 – 2011 and 2011-2012 seasons. It recorded three peaks on faba bean and cowpea plants every season. A. craccivora on faba bean was associated with three primary parasitoids being Diaeretiella rapae (M'Intosh), Aphidius colemani Viereck and Ephedrus sp. and only one Hyperparasitoid, Aphidencertus sp.. Primary parasitoid D. rapae was the highly dominant species by relative density 54.15 and 51.99%, followed by A. colemani 25.65 and 25.43%, Ephedrus sp. (14.05 and 14.07%), while the hyperparasitoid Aphidencertus sp., occurred by 6.15 and 8.51%, during 2010 /2011 and 2011 /2012 seasons, respectively. A. craccivora on cowpea was associated with only two primary parasitoids species Lysiphlebus fabarum and Trioxys sp., only one hyperparasitoid species of the family Pteromalidae. Primary parasitoid L., fabarum was the most dominant species by relative density 56.22 and 61.24%, while Trioxys sp. was recorded by 26.32 and 21.48% and Pteromalidae by 17.46 and 17.28% during 2010 and 2011 season respectively. Highest rates of parasitism 21.67% were recorded in the 2nd week of February 2010-2011 and 22.34% in the 4th week of February 2011-2012 on faba bean plants, meanwhile it were 20.37% and 11.37% in the first week of September 2010 and in the 2nd week of September during the two season cowpea plants. The seasonal means of parasitism rates were (9.80 and 8.78%), on faba bean plants during two seasons, respectively. While it obtained 8.14 and 4.68% on cowpea plants during the two season, respectively. Total developmental period of L. fabarum was investigated at three temperatures (10, 20 and 30oC). The duration was longest at 10oC. Generally, developmental periods of different stages of the parasitoid shorted as the temperature increased from 10 to 30oC, total developmental period ranged between 8.81 and 21.54 days, respectively.