Effect of weed borders on insect pests and their associated predators on sugar beet and cotton plant fields

Abstract

The study of the relationship between the important insect pests and their related predators on weeds border of the sugar beet and cotton fields was car ried out at Kafr ElSheikh region during two successive seasons, 2005/2006 and 2006/2007. Seven insect species, four insect pests and three predators were recorded o n both weeds border and sugar beet plants, while eleven insect species occurred on cotton p lants, seven insect pests and four predators. The most dominant predators were Scymnus spp., Coccinella undecimpunctata and Paederus alfierii. Significant correlation was found between Scymnus spp. on weeds and jassids on sugar beet and cotton. There was significant correlation between Scymnus spp. on weeds and on cotton plants (r = 0.502). Signficant correlation was recorded between Scymnus spp. on weeds and aphids on sugar beet (r = 0.598). On cotton plants, 97% of Scymnus spp. were larvae, while 100% of Scymnus spp. on weeds border were adults. There were relationship between the C. undecimpunctata and P. alfierii predators and Oxycarenus hyalinipennispest on weeds border (0.791) and on cotton plants (0.522*). Highly significant correlation was recorded between O. hyalinipennis on weeds border and the on cotton plants (r=0.676**) in the second season. The weeds border served as dwelling of the predators especially in winter. Scymnus spp. was common predators on Bermod grass (Cynodon dactylon). When the predator numbers began to decrease on weeds border began to increase on plant crops by third week of May.