By John Wallace and Dwight Lingenfelter
Ryelage harvest is in full swing in the southeastern part of the state and will pick up in other regions over the next few weeks. Here are a few considerations for herbicide management when harvesting cereal rye for forage.
Termination Method and Timing
Chopping cereal rye prior to anthesis is generally not an effective method of termination. Previous Penn State field trials have demonstrated that chopping rye at the late-boot stage can result in up to 80% regrowth and chopping at the mid-heading stage can result in up to 50% regrowth. Spraying cereal rye with common burndown products (glyphosate, paraquat, etc) prior to ryelage harvest is illegal. Consequently, termination of cereal rye that has been harvested for forage is best managed with post-harvest herbicide applications.
Post-harvest termination efficacy of cereal rye will be a function of herbicide program, termination timing relative to rye regrowth, and weather conditions from harvest to termination. Here are a couple tips from previous field trials at Penn State:
- Glyphosate (1.13 lb ai/ac) is generally a more effective burndown option than contact herbicides like paraquat for post-harvest termination of cereal rye.
- It is likely not necessary to delay termination after harvest to allow for regrowth when using glyphosate as long as the harvest height results in enough green leaf tissue at the base of plants to absorb the systemic herbicide and weather conditions (> 55°F) are optimal for uptake and translocation.
- If using paraquat, termination efficacy is likely to increase when application timing is delayed after harvest to allow for adequate rye regrowth.
- Cooler temperatures (< 50°F) will slow the activity of glyphosate and may impact termination efficacy of cereal rye following a mowing event.
- Consider tank-mix partners that may decrease cereal rye termination efficacy when using glyphosate, such as use of liquid N fertilizers (i.e., UAN) and clay-based herbicides like atrazine.
Observe Rotational Restrictions
As a reminder, the rotational interval listed for various crops in herbicide labels is the required amount of time from herbicide application to subsequent establishment of crops that will be used for forage or harvest value. Cereal rye that is terminated as a cover crop in the spring can be legally established following any herbicide application in the preceding crop. However, rotational intervals of herbicides applied in the preceding crop must be followed if cereal rye that is sown in the fall is then harvested as a forage the next spring. Rotation restrictions for commonly used corn and soybean herbicides can be found in the
Agronomy Guide Table 2.1-11 . Most herbicide labels include cereal rye in rotational restriction tables. However, there are several cases where the absence of cereal rye on the label requires that the maximum rotational restriction be applied, which then precludes legal forage harvest of cereal rye. This Iowa State Extension publication on
Herbicide use may restrict grazing options for cover crops provides a nice summary of which corn and soybean herbicides restrict use of fall-sown cereal rye as a spring forage.