Jerry Brust, IPM Vegetable Specialist, University of Maryland; jbrust@umd.edu
I have been working with researchers from Virginia Tech on thrips identification in their crops. They had a severe problem with thrips, especially Western flower thrips (WFT) Frankliniella occidentalis, last summer in tomato and cotton. This year they wanted to see if they were getting early (April and May) populations of Western flower thrips in their fields. Sure enough, the samples I saw from tomatoes, cotton and some winter annual weeds all had 20-50% of their thrips population as Western flower thrips. Southern parts of Maryland and the southernmost part of Delaware will probably see these Western flower thrips populations move into the area in late June and early July. This is another good reason NOT to apply any pesticides to tomato unless absolutely needed, especially early in the season. My research has shown that Western flower thrips are consistently worse on farms in our area that use pesticides on a weekly basis, whether their use is warranted or not. WFT are worse because they are usually resistant to many of the pesticides we commonly use and the frequent sprays greatly reduce natural enemies of WFT. Save your chemical sprays for later in the season when worms, thrips, mites and stink bugs may become major problems.