|Liu, Tong-Xian -|
Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 8, 2009
Publication Date: December 5, 2009
Citation: Greenberg, S.M., Liu, T., Adamczyk Jr., J.J. 2009. Thrips (Thysanoptera: Thripidae) on cotton in the Lower Rio Grande Valley of Texas: Species composition, seasonal population dynamics, damage and control. Southwestern Entomologist. 34(4):417-430. Interpretive Summary: Thrips are one of the key insects of cotton. The cotton yield losses from thrips in the last five years in the Beltwide area of the U.S. ranged from 138,000 to 172,000 bales. The cotton yield reduction from thrips is underestimated, especially in the Lower Rio Grande Valley of Texas, so far as real potential damage from thrips is in contradiction with the described situation. Management decisions about distribution and density of thrips during the cotton growing season should be based on actual field observation. Sampling is a vital component of cotton insect control. Using existing methods is difficult because thrips are microscopic and cryptic feeders. These characteristics also make thrips a difficult target for insecticides. The development of resistance to insecticides is a paramount concern with thrips. Systemic insecticides applied with the seeds, and natural enemies of thrips, especially predators, may play a significant role in suppressing strategies of thrip populations and associated environmental problems. Thrip species identification is very important in selecting a control strategy. These findings will make long-term prevention of thrip distribution and damage through a combination of tactics, including biological, cultural control, and utilizing chemical pesticides to a necessary minimum.
Technical Abstract: Species composition, population dynamics of thrips on cotton, and their predaceous natural enemies, damage and control, were determined at two different sites during three consecutive seasons from 2005 to 2007 in the Lower Rio Grande Valley (LRGV) of Texas. We observed seven different species of thrips. At locations within 0.5 kilometers from onion to cotton fields, the predominant species were western flower thrips, Frankliniella occidentalis (Pergande) (61.7%) and onion thrips, Thrips tabaci Lindeman (27.2%). Locations that were at least 50 kilometers from commercial onion growing area to cotton contained western flower thrips (68.5%) and bean thrips, Caliothrips fasciatus (Pergande) (29.2%) as predominant species. At both sites, young seedling cotton plants, from cotyledon stage to 3-4-true leaf stage, were more susceptible to onion thrips damage. Western flower thrips and bean thrips were found pre-dominantly on 5-6-true leaf stage and older cotton. Thrips were first presented in cotton at the beginning of the growing season and increased in numbers gradually, peaking in mid-May and late June. Several species of predators were found on cotton plants. Orius spp. was the most abundant predator. Heavy rainfall caused temporary reduction of thrips density on cotton plants. Thrips damage can stunt growth and reduce yield potential. The systemic insecticides thiamethoxam (CruiserTM) and imidacloprid (Gaucho GrandeTM), when applied with the seed, protected cotton from thrips damage for 30 days after planting. Foliar spray with Orthene 90S in early cotton stage could control 70-80% of thrips.