Cotton (Gossypium hirsutum) Response to Plant Protection Products using Different Spray Nozzles

Abstract

Application of dicamba to dicamba-tolerant cotton (Gossypium hirsutism L.) cultivars (Xtend Cotton, Bayer Crop Science, Research Triangle Park, NC) requires use of nozzles that deliver large spray droplets to avoid off-site movement through particle drift onto susceptible crops and other plants including endangered species. Twenty trials over a three-year period were conducted to determine if nozzles required to deliver dicamba plus glyphosate would be equally effective in delivering other pesticides including the herbicide glufosinate, the plant growth regulator mepiquat chloride, the insecticide bifenthrin plus dichrotophos and co-application of ethephon plus thidiazuron plus tribufos for removal of cotton foliage to improve harvest efficiency. Agrichemicals were applied using: a) Air Induction (AI) nozzles for agrichemicals except dicamba plus glyphosate b) Turbo Teejet Induction (TTI) nozzles for all agrichemicals c) TTI nozzles for glufosinate and dicamba plus glyphosate and AI nozzles for other agrichemicals. Applications were made in 145 L/ha at 152 kPa at a ground speed of 5 km/h. Cotton height at the end of the season, node above first fruiting branch, nodes above cracked boll, node of uppermost boll, total nodes, lint yield, and cotton fiber quality were similar regardless of nozzles used to deliver agrichemcials. Control of a complex of broadleaf signal grass (Urochloa platyphylla L.), goosegrass [Eleusine indica (L.) Gaert.], and large crabgrass (Digitaria sanguinalis L.) and Palmer amaranth (Amaranthus palmeri Watts.) was slightly lower when glufosinate was applied with TTI nozzles rather than AI nozzles. However, control of these weeds was similar regardless of nozzle selection when dicamba plus glyphosate was applied after glufosinate. These results suggest that growers can use nozzles that limit off-site movement through particle drift of agrichemicals throughout the cropping cycle with no major adverse effect on weed control and cotton growth and yield.