In conventionally managed no-till corn or soybeans, glyphosate is the preferred product of choice for burning down cereal rye. Gramoxone can also be effective, but paying attention to growth stage and using an effective tank-mixture is important.
Factors to consider in order to achieve effective control include:
1. If harvesting rye for forage, glyphosate is usually the product of choice. Delaying application following harvest for several days to allow adequate regrowth can improve control. This may not be a concern if cutting height and the presence of healthy basal leaves at application time ensures adequate control with glyphosate.
Manure application prior to herbicide application would likely reduce rye control by reducing foliar contact by the herbicide. If given the choice, apply the herbicide a day or two before manure is applied to increase the likelihood of success.
2. Glyphosate rate — most glyphosate labels recommend increasing the rate of product as the cereal rye matures. With a standard 3 lb acid/gal product where 32 fl oz is a standard rate, recommended rates range from 16 fl oz for rye that is less than 11 inches tall to 32 fl oz for rye that is greater than 18 inches tall.
On a side note, annual ryegrass (Lolium multiflorum) is different than cereal rye and is more difficult to control. Higher glyphosate rates and application at shorter ryegrass maximum heights are necessary for effective ryegrass control.
3. With glyphosate, include appropriate adjuvants in the spray tank — include 1 to 2 qt/100 gal nonionic surfactant (unless fully loaded formulation) plus 8.5 to 17 lb/100 gal AMS or equivalent. The AMS helps alleviate hard water problems and also can reduce antagonism if tank-mixing with other herbicides such as 2,4-D. Be sure to add the AMS first to the spray tank and agitate before adding the glyphosate.
4. With Gramoxone Inteon, use the 3 pt rate and remember that it is better on smaller cereals or after they have reached the boot stage and beyond. Include an appropriate adjuvant (nonionic surfactant or crop oil concentrate) and an atrazine or other photosynthesis inhibitor product (i.e. metribuzin) in the tank to increase Gramoxone activity.
5. Use a clean water source that does not contain soil or other sediment that can reduce glyphosate or Gramoxone activity.
6. Use flat fan nozzle tips that produce a uniform spray pattern and thorough coverage.
7. Spray in sufficient carrier to achieve good coverage (usually between 10 and 20 GPA for glyphosate and a minimum of 20 GPA for Gramoxone).
8. Make sure the sprayer is accurately calibrated (output, pressure, pattern, speed, etc.) to deliver the appropriate rate uniformly.
9. Air temperature before, during, and after application can influence control. Cold nights (<40 F) will reduce activity, particularly for glyphosate, and especially when followed by cool (<55 F) cloudy days.