Effect of Thrips Infestation on the Development of Cotton Seedling Diseases. P. D. Colyer, Associate Professor, Red River Research Station, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Bossier City 71113-8550. S. Micinski, and P. R. Vernon. Instructor, and Research Associate, Red River Research Station, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Bossier City 71113-8550. Plant Dis. 75:380-382. Accepted for publication 5 October 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0380.

The effect of thrips infestation on the development of cotton seedling diseases was evaluated in field plots in 1986, 1987, and 1989. The insecticide disulfoton was applied to obtain different levels of thrips infestation. When thrips were present, stands were reduced 47 and 53% less in insecticide-treated plots than in control plots in 1986 and 1989, respectively. The application of insecticide also resulted in lower disease indices. Thrips infestation was positively correlated with stand reduction (r = 0.85 in 1986 and 0.53 in 1989) and disease index (r = 0.64 in 1986 and 0.59 in 1989). In 1987, when thrips were not present, stand reduction, disease index, and plant height did not differ significantly among treatments.