Effect of Planting Date on the Efficacy of an In-Furrow Pesticide and the Development of Cotton Seedling Disease. P. D. Colyer, Associate Professor, Red River Research Station, P.O. Box 8550, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Bossier City 71113. S. Micinski, and K. T. Nguyen. Instructor, and Research Associate, Red River Research Station, P.O. Box 8550, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Bossier City 71113. Plant Dis. 75:739-742. Accepted for publication 1 February 1991. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0739.

In studies to evaluate the effect of planting date and application of aldicarb + TSX on the development of seedling diseases of cotton (Gossypium hirsutum), disease was assessed by quantifying seedling populations and indexing surviving seedlings. In both 1985 and 1986, eight planting dates between 4 April and 16 May were evaluated. Plant populations generally increased with later planting dates. The increase in plant populations over planting date for the untreated plots was described by a cubic equation (R² = 0.33) in 1985. No significant relationship was observed for the plots treated with aldicarb + TSX. In 1986, the relationship between plant populations and planting date was described by a cubic equation for the treated and untreated plots (R² = 0.85 and 0.86, respectively). The application of aldicarb + TSX also increased seedling stand density compared with the controls. Values of the disease indices were higher for the early plantings and lower in the later plantings. The decline in disease index over planting dates in 1985 was described by a quadratic equation for the untreated plots (R² = 0.86) and by a cubic equation for the treated plots (R² = 0.87). In 1986, the relationship between disease index and planting dates was described by a cubic equation for untreated and treated plots (R² = 0.69 and 0.52, respectively). Values of the disease index were significantly reduced by the application of aldicarb + TSX at all planting dates.