Cut leaf evening primrose, wild radish, and horseweed are some of the most troublesome weeds in conservation tillage systems. Allowed to grow, these winter weeds become very large and hard to kill by spring planting time. The most consistent and effective burndown program for these winter weeds is a 2,4-D application in February when they are small.
Another advantage of spraying 2,4-D in February is that it is a much safer time than spraying in the spring. It will also allow enough time to meet the plant back interval required before planting cotton, which is around 28 days, depending on which formulation you use. This is important. I get several calls each spring from growers wanting to spray 2,4-D for these weeds, but can’t due to the plant back interval and their desired planting date.
Recent research has determined that 2,4-D amine is as effective as the ester formulation of 2,4-D in weed control. This is good news since amine formulations are less volatile than the esters.
The lb. ai/A rates of 2,4-D amine will vary depending on which weed you are targeting:
Cut leaf Evening Primrose: Apply 0.24-0.38 lb. ai/A
Wild Radish: Apply 0.5-0.75 lb. ai/A
Horseweed: Apply 0.75 lb. ai/A
Glyphosate Resistant Horseweed: Apply 0.95 lb. ai/A
Three formulations of 2,4-D amine are available with the following use rates:
2,4-D 4S – Rate is 12-24 ounces/A
2,4-D 4.7S – Rate is 10-20 ounces/A
2,4-D 5S – Rate is 9-18 ounces/A
Spraying 2,4-D in February will get you a good head start on these tough weeds. Follow-up with your normal pre-plant burndown treatments in the spring and you should be ahead of game.