COTTON DAMAGE from 2,4-D is being seen in all cotton producing areas in Oklahoma, according to J. C. Banks, Oklahoma State University Extension state cotton specialist.
“In all cotton producing areas in the state, the crop has been showing symptoms of phenoxy (2,4-D) herbicide injury,” he said. “There are a lot of issues (political and otherwise) about in-season use of 2,4-D in cotton producing areas, but for now we need to emphasize how to work through the injury.
“The first thing to do is register the drift complaint with the Oklahoma Department of Agriculture. Hopefully, they can identify the source of drift and help prevent problems in the future. Next, we need to determine what needs to be done to the crop to get back into production as soon as possible.
“There are many misconceptions on the availability of spray-on products that are supposed to help the plant recover, and how much the injury will cause a reduction in yield. Nutrient solutions or specific plant growth regulators are a waste of time and money unless the plant is suffering from a nutrient deficiency prior to the injury.
“Drift rates of 2,4-D on cotton will always cause visible damage to the cotton and a delay in maturity. Normally, this results in a loss of yield primarily due to delayed fruiting caused by loss of fruit to exposure and inadequate time to mature bolls set later.
“If we have a warm fall and a late frost this effect will be minimized, but it will be more expensive to keep the plant fruiting into the fall.
“Some work by Wayne Keeling with Texas A&M University, Lubbock, has determined that the most significant yield loss results from injury at the six to eight leaf or early squaring stage of cotton. This normally occurs 30 to 40 days after planting. The primary question I’ve been asked is: ‘Is it cost effective to continue to take care of the plant or should I abandon the most severely affected areas?’ If the cotton is irrigated, and needs irrigation, you should irrigate to allow the plant to attempt to grow out of the injury.
“At pinhead square, we usually try to apply an insecticide to control fleahoppers. Since a severely injured plant will either not produce squares, or if produced, they will fall off prior to bloom, my recommendation is to delay the fleahopper spray until the top new leaf in the terminal of the plant is no longer severely strapped. When the leaf is somewhat normally shaped, even if it has wavy edges, a normal square can be produced and expected to produce fruit.
“The fleahopper application should be made at this time. If new growth is normal at first bloom, and the plant is growing rapidly, a mepiquat growth regulator should be used to keep the plant from excessive vegetative growth due to a loss of earlier fruit. This growth regulator should not be applied immediately following the injury but when the plant has had time to recover. Growth regulators are somewhat of a stress to the plant, and we do not need to add this stress to the stress of phenoxy injury. Hopefully, the weather will allow a delay in cutout as we approach the end of the season so a maximum number of bolls will be set.”