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Oklahoma State University Stillwater, OK |
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Oklahoma Alfalfa |
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Oklahoma State University Stillwater, OK |
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Oklahoma Alfalfa |
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Weed-it Tips It is important to scout your fields as soon as possible to determine if you have enough alfalfa plants to have a stand. Basically, if you do not have 10 alfalfa plants per square foot over the entire area, then you do not have a full stand and will need to try to thicken it up next spring or till the area and replant next spring or fall. Many new stands that were planted have volunteer wheat and some cheat in them, and it is important to control these grasses this fall if they are currently larger than the alfalfa and starting to shade the alfalfa plants. Most weeds emerge at the same time as alfalfa, and they continue actively growing until a hard freeze (10o to 15o F). These grasses can still be control this fall with herbicides, providing we get a warm day sometime in November or early December. For best results, spray weeds on a sunny day (shirtsleeve weather). Herbicide choices for controlling volunteer wheat and other grasses in fall-planted alfalfa include fall applications of Poast Plus and Select 2 EC. Select 2EC received label clearance for use on alfalfa for control of weedy grasses on April 6, 1998. Volunteer cereals, some of the bromus species, and ryegrass are listed as controlled with 6 fl. oz/acre when plants are 26 inches tall. We had one experiment where we compared cool-season grass control with Select 2 EC and Poast Plus. Control of wheat and ryegrass in that study was "good to excellent" with both herbicides, but control of downy brome was only "fair". Control of cheat and rescue-grass was "good to excellent" with Poast Plus and only "fair" with Select 2 EC. I would recommend trying Select 2 EC on limited acres until we learn more about how it is going to control cool-season grasses in fall-planted alfalfa. For control of most broadleaf weeds (including seedling dock), use of Butyrac (2,4DB) in the fall is the best choice. However, it is very important to spray weeds in the fall while they are small and in the rosette growth-stage. Many of the weeds are not controlled with spring applications of Butyrac. Shepherd's purse and treacle mustard are seldom controlled with spring spraying of Butyrac, and producers are usually very disappointed with spring spray results. That's why it is so important to examine fall-planted alfalfa now and get them sprayed this fall.
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| Jim Stritzke Former Alfalfa Weed Control Specialist Department of Plant and Soil Sciences Oklahoma State University |
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