Doctor of Philosophy (PhD)



Document Type



The common species of thrips infesting cotton seedlings include flower thrips, Frankliniella tritici (Fitch); tobacco thrips, Frankliniella fusca (Hinds); western flower thrips, Frankliniella occidentalis (Pergande); onion thrips, Thrips tabaci (Lindeman); and soybean thrips, Neohydatothrips variabilis (Beach). In surveys of cotton seedlings at several locations in Louisiana, tobacco thrips was the most common species. The occurrence of flower thrips and soybean thrips was variable. Western flower thrips accounted for < 15% of adults collected at all locations, except two. The performance of acephate and imidacloprid applied as seed treatments and in-furrow, and aldicarb applied in-furrow was evaluated for thrips management across different production environments. Insecticide treatments reduced thrips densities and delayed development of thrips larval populations. The at-planting insecticides influenced thrips species composition in some instances. In studies to evaluate the effects of winter-spring vegetation type (native vegetation and wheat) on aldicarb efficacy, vegetation type did not influence thrips densities on cotton, with one exception. Aldicarb reduced thrips densities regardless of vegetation type. Vegetation type or insecticide treatments did not influence lint yield. Increasing aldicarb rates generally did not improve thrips control. Aldicarb rates currently recommended in conventional tillage systems should be adequate for systems that incorporate winter-spring vegetation as cover crops. Additional studies were conducted to further investigate the influence of thrips on crop maturity and yield. The addition of an at-planting insecticide improved lint yield in one of six tests. Thrips infestations did not affect crop maturity, and with few exceptions boll distribution and boll retention. The majority of these exceptions were associated with the test where the addition of an at-planting insecticide improved lint yield. Several soil applied at-planting insecticides were evaluated against tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), in a field caged infestation study. Acephate and imidacloprid provided little control of tarnished plant bugs. Thiamethoxam and aldicarb resulted in ≥ 50% tarnished plant bug mortality until 10 and 18 DAE, respectively. These are the first reports of western flower thrips infesting cotton seedlings in Louisiana. The addition of an at-planting insecticide provided control of thrips, but affects on crop maturity and yield were variable.



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Committee Chair

Billy Rogers Leonard



Included in

Entomology Commons