Seasonal abundance and population dynamics of certain sucking insects on soybean in Kafr El-Sheikh Governorate, Egypt

Abstract

The population density of aphids ( Aphis spp.), whitefly ( Bemisia tabaci), thrips ( Thrips tabaci) and jassids ( Empoasca spp.) was studied on soyabean in relation to common associated predators ( Paederus alfierii, Chrysoperla carnea, Coccinella undecimpunctata and Scymnus spp.) and some prevailing climatic factors (temperature, relative humidity and wind speed) during 1992 and 1993, in Kafr El-Sheikh Governorate, Egypt. Results indicated that the populations of the considered insect pests and associated predators were higher in the second season than in the first one. Every insect pest had one abundance peak, which coincided with the others. The whitefly, thrips and jassids had one generation, while the aphids had 2 generations a season. The total population of the associated predators peaked twice annually. The first peak appeared in the second half of July for the two seasons while the second peak appeared on 27 September for the 1992 season and on 6 September for the 1993 season. The combined effect of the weekly mean of predator populations, daily mean temperature, relative humidity and wind speed was responsible for 84.76, 73.9, 68.70 and 58% of changes in the populations of jassids, thrips, whitefly and aphids, respectively, in the first season, and for 79.40, 54.80, 66.30 and 45.8%, respectively, in the second season.