Determination of the efect of thrips lind. (Thysanoptera: Thripidae)population on the cotton plant development and yield in Harran plan conditions

In this study, the effect of Thrips tasaci Lind. on cotton plant development and yield were investigated by survey and established trials in Harran plain. Throughout the survey period in 1996 and 1998, T. tabaci population was not develop at the same denstiy in every year. When the high population was occured the economic yield losses was resulted. In basic plant growth stage regarding to T. tabaci population increasing, square and boll development retrograded, number of opened boll and yield decreased in plant, plot and field experiments. In all trials, T. tabaci population was exceed Economic Injury Threshold (EIT) described by tecnical directions as 15 % infested plant. In many characters when the T. tabaci population exceed this EIT, yield losses was lower than the cost the of the yield estimated for one spraying. In the plants, increases of T. tabaci population over 4-5 individuals/leaf the estimated yield losses was much more than the yield quantity estimated for one spray Key Words :Thrips tabaci Lind., Cotton (Gossypium hirsutum L.), Harran Plain, GAP