– Stan Smith, OSU Extension PA, Fairfield County
Upon completing the alfalfa stand evaluation Rory discusses above, if you decide its time to replace an old stand after a first cutting harvest, don’t forget that the label of many glyphosate products allows for a pre hay harvest application to kill the existing stand. The Ohio/Indiana Weed Control Guide recommends the following:
* Some glyphosate products can be used in declining alfalfa stands where crop destruction is desirable or acceptable.
* Mode of action: group 9 (see page 22-23 of the Weed Control Guide)
* A preharvest application will control annual and perennial weeds, and greatly improve control of alfalfa and perennial grasses compared to application after harvest.
* Apply in a spray volume of 3 to 10 gpa just prior to alfalfa harvest in spring or fall.
* Allow a minimum of 36 hours between application and harvest. Optimum harvest time is 3 to 7 days after application to maintain hay quality and maximize perennial control.
* The treated alfalfa can be fed to any livestock including lactating animals.
* If the field is planted to corn following alfalfa harvest, including atrazine in the preplant/preemergence herbicide program will aid in control of perennial grasses. Postemergence application of dicamba or dicamba + 2,4-D may be required for complete control of alfalfa in the corn.