Effect of Intercropping and Neighbor Systems of Cotton Plants and Other Summer Crops on the Occurrance of Some Cotton Pests and Associated Natural Enemies

Abstract

This study was conducted to evaluate the effect of intercropping and neighbor cotton plants with other summer plants on the occurrence levels of some cotton pests in Graia village at Zagazig, Sharkia Governorate during 2003 and 2004 seasons. The results show that Intercropping cotton with tomato or onion increased Aphis gossypii ( Glover) average numbers significantly on cotton plants. While with cucumber and pepper the average numbers were decreased in both 2003 and 2004 seasons. The average numbers of Tetranychus spp. increased in intercropping system of cotton with tomato or cucumber, while the contrast results was found with onion or pepper intercropping system in comparing with the solid cotton plants during 2003 and 2004 seasons. The all intercropping systems increased the population density of Thrips tabaci (Lind.) on cotton plants in comparable with solid plants in both of seasons. The influences of intercropping systems on Bemisia tabaci (Genn.) and Empoasca sp. were differed from season to another and from system to another. With respect to the occurrence of associated natural enemies under intercropping systems, the highest population density of predators, Scymnus spp. and Orius spp. were recorded on cotton plants intercropped with tomato in both seasons. While, the highest number of predators ( Syrphus sp.,) Paederus alfierii, true spider mites, predator mite (Phytoseiulus sp.) and parasitoids, Encarsia sp. and Ertmocerus sp. were recorded on solid cotton plants compared to the intercropping systems in the two study seasons. The highest numbers of Chrysoperla carnea were detected on cotton plants intercropped with cucumber, whereas, the highest average number of Coccinella spp. recorded on cotton plants intercropped with onion in the first season and cotton plants intercropped with tomato in the second one. As neighbor effect, the numbers of Empoasca sp. and T.tabaci was increased on cotton plants, while the numbers of A. gossypii, B. tabaci and Tetranychus spp. were decreased in both of seasons 2003 and 2004. The neighbor of cotton plants by tomato, cucumber, onion or pepper was increased the numbers of predators (Chrysoperla carnea, Orius spp., Paederus alfierii) and parasitoid, Encarsia sp. on cotton plants; while the numbers of Coccinella spp. Scymnus spp., Syrphus spp., true spider mites and Ertmocerns sp. were decreased in both seasons.