The first important step in controlling annual ryegrass used as a cover crop is the timing of the burndown.
- It is best done when the plant is small, 6-9” in height, and preferably before the first node has developed. Typically, this happens in late March to late-April depending on weather and farm location.
- Make sure the crop is actively growing, so as to optimize the uptake of the herbicide (glyphosate).
- Daytime minimum temperature should be at 55 degrees (F) and above 60 is better. • If night temperatures drop below 38, wait three days before spraying. • Soil temperatures should be above 45.
Early termination of the cover crop makes control easier and reduces the amount of residue into which you’ll plant corn or soybeans.
- Early control also facilitates soil dry-down, allows for significant decomposition of annual ryegrass residue and release of nutrients for uptake by the corn or soybean crop.
Some growers have found it easier to plant into the annual ryegrass first and then apply a burndown. Warmer weather conditions improve glyphosate activity and planting into green vegetation has been successful, and is often easier than planting into a “half-dead” cover crop.
Warm temperatures and actively growing annual ryegrass plants are a must for effective control.
- Use a thorough spray coverage using moderate spray pressure and a medium spray droplet size. Don’t use air induction spray systems or nozzles that produce coarse droplets.
- The application rate should be about 8-12 gallons per acre.
- Spray at least 4 hours prior to sunset to allow for maximum translocation of the glyphosate within the plant.
- While one burn-down herbicide application often provides control of the annual ryegrass. Inspect the results and then be ready for a second application if needed. (If you use too weak an herbicide solution, it will make the plant more resistant and more difficult to control later.)
- Apply glyphosate at 1.25-1.50 lb a.e./a with ammonium sulfate and surfactant. Follow label directions carefully with respect to pH and mixing order. It is important when adding ammonium sulfate, buffering agents or water conditioners that they be added to the full spray tank of water and agitated for 3-5 minutes before adding the glyphosate. Additional NIS surfactant, if called for, is normally added last.
- Weather conditions affect how well glyphosate controls annual ryegrass and a second application may be required.