Killing annual ryegrass in the spring (glyphosate is the most common and effective herbicide used)  is best done in warm weather. While warm weather is ideal for uptake of glyphosate, satisfactory results can also occur in cooler weather. In that case, however, it is very important to apply the burndown before the plants reach the joint stage.

The date of annual ryegrass reaching the joint stage will vary depending on the date planted, the amount of fall growth and the weather during winter and early spring.  Annual ryegrass can be a challenge to burndown if the herbicide application is applied at a time when there is cool, cloudy and wet weather and annual ryegrass is past the joint stage.  Burndown is typically done when the annual ryegrass is 6-9 inches tall but it may be 12-16 inches depending on spring weather.

Here are some guidelines for controlling annual ryegrass, no matter what the springtime conditions.

BURNDOWN

Warm temperatures

1. One burndown application with glyphosate will generally provide a near perfect kill with warm temperatures. Daytime temperatures in the 50s or 60s and nighttime temperature in the 40s are needed for good glyphosate translocation.
2. One night of mid 30’s should not drastically affect performance.
3. Cloudy and wet weather may slow glyphosate translocation.
4. Annual ryegrass may “green back up” even when it initially appeared to be completely killed.  Residual herbicide and/or post-application are then necessary.

 

Cool temperatures

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.

1. 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.
2. Spraying a couple of hours before sundown with temperatures expected below the mid 30s will result in poor burndown results.
3. A second burndown application is frequently needed to kill annual ryegrass if weather conditions in early spring are cool and cloudy.
4. 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.   

Application rate

1. Glyphosate – use full label rate of 32 oz/ac (check glyphosate formulation for labeled rate)
2. Add 8 oz/ac of 2,4-D to help control winter annuals
3. Carrier – only apply 7-10 gals/ac; applying 15 to 20 gal/ac dilutes the glyphosate and reduces performance (compounded with cool temperatures)
4. 15 gal/ac + of carrier can be applied under warm conditions
5. Adding AMS or citric acid to adjust the water’s pH is critical for expected results
6. May want to add 0.25% more surfactant if using generic glyphosate
7. Adding crop oil decreases glyphosate uptake

 

 Other herbicides 

1. Simazine can be added to the glyphosate tank mix

   a.  Simazine requires at least 2 inches of rainfall to be fully activate

   b.  Simazine is absorbed by the new shoots and prevents them from growing

2. Atrazine, or 28%, should not be added to the glyphosatge tank mix (these products cause leaf burn and reduce glyphosate absorption)
3. Atrazine can be applied 14-21 days after glyphosate application at a rate of 2 to 2.5 lbs/ac plus crop oil (atrazine needs 2 inches of rainfall to activate)

Nozzles

1. Flat fan nozzles should be used at 20-40 psi
2. DO NOT use flood jet nozzles
3. Do not use an air induction sprayer
4. Excessive boom bounce can cause improper overlap and results in “streaks”.

Water

1. Water should be free of any clay particles (pond water) as it will tie up the glyphosate.
2. A softening agent may enhance performance if hard water is being used.

Tips for Using Gramoxone as a Burndown

1. Provides quicker burndown but is not translocated
2. Apply at 30-40 psi and with 20-40 gal/ac of carrier using flat fan nozzles
   •  Higher volume is needed for taller annual ryegrass
   • Use clean water as a carrier that is free of clay particles.
   • 28% N or other clear liquid fertilizer can be used as a carrier
3. Add nonionic surfactant
4. Simazine or atrazine added to the tank mix reduces uptake and results in slower kill
5. Add crop oil to mixture
6. Adding 8 oz/ac of 2,4-D helps kill winter annuals.

 Order of Mixing

1. Fill spray tank ½ full of carrier
2. Begin tank agitation and continue while mixing and spraying.
3. Add any dry and then liquid formulations.
4. Add either Glyphosate or Gramoxone to tank
5. Then add nonionic surfactant
6. Fill remainder of tank  

Post Applied Options

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

            a.  Atrazine (2 to 21/2 lb/ac) and crop oil 

            b.  Steadfast - 3/4 oz/ac, include adjuvant, 28%, Crop oil concentrate, 15 gal/ac water; 20-40 psi  

                 with flat fan nozzles

            c.  Option - 1.5 pts/ac; include adjuvant, 28%, yellowing of corn may occur; use of organophosphate

                 insecticide may increase crop injury -see label

            d.  Accent – 2/3 oz/ac; can be used on bigger corn; include adjuvant, 28%, Crop oil concentrate  

Mention of any product does not constitute any type of endorsement or guarantee.