With the late spring and extra rain, there may be some who waited for the annual ryegrass crop to mature and for the conditions to improve enough to spray the grass with glyphosate. Here are some tips for applying the herbicide in cooler temperatures. Following that, there are some cautions about annual ryegrass control and some tips on post-emergence management.
The desired burndown may not be achieved if daytime temperatures are in the 40s and nighttime temperatures are consistently below the 20s to mid 30s. With these temperatures it may take 3-4 weeks and a second application for a complete kill.
If night time temperatures are in the 30s or low 40s, spraying should not begin until the dew has dried. Application, in that case, should stop at mid afternoon in order to allow sufficient time (around 5 hours) for glyphosate translocation. The timing of spraying is not an exact science but generally the more time for translocation, the more effective the burndown.
Spraying a couple of hours before sundown with temperatures expected below the mid 30s will result in poor burndown results.
A second burndown application is frequently needed to kill annual ryegrass if weather conditions in early spring are cool and cloudy.
Use a full rate of glyphosate and only apply 7-10 gal/ac of water, with flat fan nozzles, in order to concentrate the glyphosate.
Post emergence management:
1. If glyphosate tolerant crops were planted, wait until there is 2-4 inches of annual ryegrass regrowth before spraying
2. Conventional corn options – Annual ryegrass should be less than 6 inches in height and temperature 70 degrees
Atrazine (2 to 2 1/2 lb/ac) and crop oil
Steadfast - 3/4 oz/ac, include adjuvant, 28% N, Crop oil concentrate, 15 gal/ac water; 20-40 psi with flat fan nozzles
Option – 1.5 oz/ac; include adjuvant, 28% N, yellowing of corn may occur; use of organophosphate insecticide may increase crop injury -see label
Accent – 2/3 oz/ac; can be used on bigger corn; include adjuvant, 28% N, Crop oil concentrate
For more information, see the annual ryegrass website, and look under “management”.