INFLUENCE OF WEED REMOVAL AND INFESTATION PERIODS ON MAIN INSECTS INFESTING COMMON BEAN AND THEIR NATURAL ENEMIES AND PRODACTIVITY AT SOHAG GOVERNORAT

Abstract

Two field experiments were conducted at the farm of Shandweel Agricultural Research Station, Sohag Governorate during seasons of 2016 and 2017 in summer plantation to investigate the effect of weed removal and infestation periods on major insect pests, their associated predators, and productivity of common bean. Eight weed removal and infestation periods were studied in complete randomized block design. In the plots of weed-free, the weed removed for 3, 6, 9, and 12 weeks after emergence, then weeds were left to the end of the growing season. For weed-infested plots, the weed was left to compete with the crop for 3, 6, 9, and 12 weeks after emergence, and then removed to the end of the growing season. Data revealed that the weeding systems affected significantly the populations of Bemisia tabaci (Genn.), Empoasca decipiens (Paoli), Aphis craccivora Koch., Thrips tabaci Lind., Coccinella undecimpunctata L. and Chrysoperla carnea (Steph.) in both seasons of the study. While no significant effect was found for Liriomyza trifolii Burg. in both seasons. It could be included that B. tabaci infestation increased with decreasing weeding frequency. In contrast, E. decipiens and A. craccivora infestation decreased with decreasing weeding frequency. C. undecimpunctata and Ch. carnea increased in weedy common bean plots than free plots. Fresh weight and dry matter of total annual weeds reduced significantly by increased weed-free period, but the previous traits increasing by increasing weed competition period. In contrast, with 100 seeds weight and seed yield per feddan, the yield increased significantly by increasing weed-free period, but decreased by increasing weed competition period.