Farmers have been successfully controlling annual ryegrass, as a cover crop in the Midwest, for more than 20 years. If somebody tells you “it’s a weed,” tell them politely, “Yes, I know, and it’s possible to control it if you know what you’re doing!”
Here are a few tips from those online sources:
- Don’t let annual ryegrass stay around too long in the spring: kill it before the “joint” stage when the grass is between 4 and 8 inches tall. By now, the grass is active, so watch it carefully to optimize herbicide effectiveness
- Wait for the right weather: daytime temps above 55 consistently; no rain, preferably spray earlier in the day to allow for maximum uptake by the plant before sundown and cooler temps
- Use the right sprayer: don’t use a sprayer with coarse droplets
- USE THE RATE LISTED ON THE LABEL. Don’t scrimp here. You don’t want the herbicide to fail, then have to battle annual ryegrass that comes back with more tolerance.
- Spray again if you see any lingering color after a week. Use another herbicide with a different mode of action
- Getting the pH of the water right is important: add ammonium sulfate with a surfactant to the water BEFORE adding the glyphosate to the tank.