An abundance study of Thrips tabaci (Thys.: Thripidae) on different genotypes of eggplant in Varamin region, Iran

Abundance of Thrips tabaci Lind., an important pest of vegetables, was investigated on upper and lower leaves of different genotypes of eggplant, including Siah-Mashhad, Borazjan, Black beauty, Siah-Neyshabour, Zabul indigenous, Imami-905, Juybar-Mazandaran, Sarkhoun-Hormozgan and Galami-Varamin, during 2000-2001 in Varamin region. Eggplant seedlings were cultivated in May in a randomized complete block design with three replications. Each replication consisted of four rows of 10 plants. Five leaves were randomly sampled at weekly intervals until October to estimate the incidence and population fluctuation of T. tabaci. The number of thrips was counted on the surface of four square centimeters of leaves using a binocular microscope. All analyses and comparisons were carried out using statistical package SAS. The results showed that there was a significant difference between the number of thrips on upper and lower leaves, so that the number of thrips on lower leaves were several times higher than that of on upper leaves. Borazjan and Juybar-Mazandaran with the mean number of 1.55 and 0.86 had the highest population in 2000 and 2001, respectively. In complex analysis, there was no significant difference between the thrips abundance on lower and upper leaves. Incidence of thrips faced with increase from June, and the maximum number was recorded in early until late July in both years. The results indicated that, a trend of increase initiated from late June in Varamin. Borazjan had more thrips than other genotypes and the thrips abundance in the first year was two times of the second year.