POPULATION FLUCTUATION OF THRIPS, WHITEFLY AND ASSOCIATED PREDATORS IN CABBAGE PLANTATIONS AS INFLUENCED BY WEATHER FACTORS AND TOXIC COMPOUNDS

Field experiments were conducted during two successive cabbage growing seasons (2008/09 and 2009/10( at El-Riad district, Kafr El-Sheikh Governorate. The objective was to study the population fluctuation of thrips, Thrips tabaci Lind., whitefly, Bemisia tabaci (Genn.) and their predators (Chrysoperla carnea and true spiders) in cabbage plantations. The toxicity of Marshal and Bermectine in reducing the population density of T. tabaci and B. tabaci infesting cabbage was evaluated. Also, the side effect of these compounds on Chrysoperla carnea and true spiders was assessed. Beside the effect of weather factors (mean temperature, relative humidity and wind velocity). Population fluctuations of T. tabaci  reached maximal abundance in March and early April in both seasons .B. tabaci was the earliest insect, among sucking pests, to attack cabbage plants, the population fluctuations reached maximal abundance in September and October in the both seasons. Highest abundance of C. carnea occurred in early November and April in the first season while it occurred in January and February in the second season. In both seasons, the maximum number of true spiders was detected in October and April. Temperature had a highly significant negative effect on thrips infestations, while wind velocity had a highly significant positive correlation with thrips in the first season. Whitefly tended to increase with an increase in the median temperature. True spiders correlated highly significant and negatively with whitelfy in the first season. The joint effect of  weathering factors  and predators on the populations of thrips and whitefly was higher in first season than in second season. Marshal and Bermectine under field conditions caused reduction in infestation of T. tabaci. The effects of both compounds on whitefly (mature and immature stages) were high to moderate. Concerning the side effects on the predators, Marshal induced moderate effect while Bermectine exhibited a slight effect against C. carnea and true spiders.