Winter crop, tillage, and planting date effects on double-crop cotton

Canola (Brassica napus L.) can be profitably grown as a winter crop in a double-crop system in the southeastern USA. However, stand reductions of double-cropped cotton (Gossypium hirsutum L.) following canola have been observed. Field experiments were conducted over 2 T to examine the effects of previous crop, tillage, planting date, and pesticide use on stand establishment of double-cropped cotton. In all 1999 experiments, cotton stand and seed cotton yields were reduced following canola compared with following winter wheat (Triticum aestivum L.). In four of five comparisons, cotton seedling infection by Rhizoctonia solani was greater following canola than following wheat or fallow. All R. solani isolates were anastomosis group AG-4, indicating that canola production did not selectively increase an unusual biotype of R. solani. In both years, R. solani AG-4 infection rates were enhanced by use of aldicarb [2-methyl-2-(methylthio) propionaldehyde O-(methylcarbamoyl)oxime] granular insecticide regardless of the preceding winter crop. The fungicide treatment did not prevent seedling infection by R. solani but did reduce stand and yield losses in 1999. Tillage had no consistent affect on R. solani AG-4 infection, stand, or yield following any winter crop treatment. Delayed cotton planting also did not consistently affect R. solani AG-4 infection or cotton stand but did reduce seed cotton yield at Tifton. Thus, modified tillage practices and delayed cotton planting are not viable management tools for controlling R. solani AG-4 infection and minimizing stand losses of cotton when double-cropped following canola.