Incidence and control of thrips on outdoor lettuce at Pukekohe

Abstract

Western flower thrips and onion thrips were the dominant thrips species on lettuce in 10 field trials undertaken at Pukekohe (South Auckland, New Zealand) between 2002 and 2005. This is the first record of western flower thrips on outdoor lettuce. Intonsa flower thrips was also found in lettuce for the first time. Both flower thrips species are vectors of Tomato spotted wilt virus but this virus was not observed in these trials. Thrips populations peaked in summer (Dec-Feb) with greatest numbers on 4 Feb 2003 (mean of 8/lettuce). The low number of thrips on the lettuce and the low rate of reproduction indicate that lettuce is a poor host plant, Thrips feeding damage was not sufficient for harvested lettuce to be down-graded in any of the trials. Imidacloprid seedling drenches applied to control currant lettuce aphid did not reduce thrips numbers. Methamidophos was the most effective insecticide for control of thrips in lettuce.