Spring weather patterns have led to variability in planting progress across the state. Some parts of Ohio have made strides thanks to early warm temperatures and dry soils, and others have hardly started due to untimely, excessive rainfall. A couple of questions have been recurring this spring, related to the control of ryegrass (annual/Italian) in burndown situations, and the effective termination of cover crops.

Weed scientists generally don’t recommend the use of annual ryegrass as a cover crop, as it is an aggressive species, tends to escape control tactics, and can quickly become a weed issue in grain crops. Ryegrass can pop up in crop fields due to cover crop control failures, roadside grass plantings, or contaminated seed.

There are some general guidelines to improve the control of ryegrass. These include:

  • Herbicide applications before plants reach 6-8 inches in height lead to the most consistent control.
  • Use 1.5-2.5 lbs ae per acre of glyphosate for a complete kill. Adding 1 oz of saflufenacil (Sharpen) or 1 oz of tiafenacil (Reviton) can increase control of annual ryegrass, and higher rates don’t necessarily improve control.
  • Control is most effective when plants are actively growing, and nighttime temperatures remain above 45F for 2 to 3 day prior to and after application.
  • There have been reports of poor control with glyphosate in Ohio, and we know resistance is an issue in areas across the region. Where control issues have occurred, mixtures of gramoxone + metribuzin or atrazine + 2,4-D or dicamba can control plants smaller than 6 inches. Clethodim + glyphosate is an option ahead of soybean, although control can be slow, especially under cool weather conditions.
  • Group 5 herbicides (atrazine and metribuzin) can antagonize glyphosate efficacy on ryegrass when applied in tank mixtures.
  • Preliminary data from UK suggests that 28% UAN as a carrier for glyphosate may result in poor control of ryegrass.
  • Ryegrass control is most effective in the fall. Where not adequately killed with either a fall or spring burndown application, control options for large plants present at the time of planting are limited.
The speed of small grain (cereal rye, wheat, barley, etc.) cover crop termination has also been in question this spring. Here’s some general reminders about cover crop termination:

  • Weather conditions at the time of application and shortly after can influence efficacy and speed of kill. Cool, cloudy conditions and low nighttime temperatures can slow the rate of control.
  • It may take 14-21 days for a complete kill in these conditions.
  • Increased glyphosate rates may be necessary on taller cover crops and in cool conditions.
  • Grass cover crop species are most effectively terminated with glyphosate alone or in combination with saflufenacil.
  • Broadleaf cover crop species are most effectively terminated with mixtures of glyphosate + 2,4-D, dicamba, or saflufenacil.
  • Check herbicide labels for crop rotation restrictions when planning cover crop termination applications, especially for Group 1 and 4 herbicides.

Related Content:

Differences between Cereal Rye and Ryegrass for Cover Crops,

Planting into Ryelage or Cover Crop Rye That Has Gotten Away,

EPA’s Proposed Herbicide Strategy & What it Means for Herbicide Use