Early summer can be the best time to control weeds in grass hay pastures, although the fall is a good time to use systemic herbicides on mowed or grazed pastures. Biennials like common burdock and bull and musk thistles are easy to kill while still in the rosette growth stage, like dandelions on your lawn.
When these weeds awaken in the spring, they grow swiftly to reproduce, making weed control difficult. Sept. 1 to Oct. 31 is an excellent time to apply weed killers, yet biennial and perennial weeds need sufficient healthy leaf surface to absorb herbicides.
Weather conditions need to be favorable such as air temperatures immediately before, during, and post-application. The warmer, the better to tackle your weed problem, with daytime temperatures in the mid-50s. (Learn Why Do Weeds Grow So Fast) Cold nights and overcast days can reduce the effectiveness of treatment for removing weeds.
However, there is more to it for the best pasture herbicide, so in our pasture herbicide guide, you can find more about the ideal conditions, and which are the best chemicals to use in pasture weed sprayers.
Pasture Weed Control Strategies
Examine your pastures for weeds. Assess overstocking and alter your grazing management plan to fit available forage.
Identify Weeds Of Concern
The herbicides you use, and their recommended application rates will depend on the weed species and the time of year.
This control of herbicide is most cost-effective for many weeds, and is used for brush control if woody plants are present or are the dominant species
Weed and brush control is available in some products or by tank mixing.
Spray At The Right Time
2” tall annual weeds are susceptible early in the season when they are actively growing.
The lowest labeled rates will then apply. A broad-spectrum herbicide will control weeds that germinate after spraying with residual control.
Contact herbicides like 2,4-D only work on emerging weeds and won’t control weeds that sprout after application.
Treat weeds while they are actively growing but before flowering and seed production. Remember to increase herbicide rates as the plants mature during their life cycle.
Mow Before Spraying
Herbicides won’t control weeds that aren’t actively growing. So, spray only if you’re willing to give up control. (Read What Kills Weeds Permanently)
Mowing biennial and perennial plants prepares them for fall treatment.
Follow Directions
Apply the recommended herbicide rate in 10-20 gallons of total spray mixture per acre for ground broadcast. Use at least 20 gallons/acre for brush control. Soak weeds or brush well with an ag surfactant at the recommended dosage.
Consider using a drift-control additive to optimize deposition.
Take caution with pesticides that offer good soil residual action for killing weeds. They should not be used on agricultural or crop rotation land.
Sheep feces and urine transmit herbicide residues from herbicide-treated grasses to the soil.
Read and follow all label precautions that offer more on weed identification, rate, and timing recommendations for rangeland and pasture weeds.
Common pasture herbicide examples:
Clarity 4S or Banvel 4S is a systemic herbicide that suppresses or controls many annual and biennial broadleaf weeds and many perennials. Clarity/Banvel is often tank mixed with other herbicides (e.g., 2, 4-D).
Cimarron (metsulfuron-methyl) is an inhibitor herbicide that controls many annual, biennial, and perennial broadleaf weeds.
For established warm or cool-season grass stands. Apply one year after establishment (minimum six months) for most species; timothy and fescue require longer.
The weed control spectrum increases by tank-mixing it with 2, 4-D, or dicamba.
This control effectively controls weeds such as Canada thistle, bull, musk, plumeless thistle, and multiflora, rose. The spray solution must contain COC or NIS.
Grazing and haying are not restricted in Cimarron. Thus, animal and livestock health shouldn’t be an issue.
Newer active component for hay and pasture, Milestone (aminopyralid).
In addition to Canada, bull, musk, and plumeless thistles, Milestone is effective against a variety of other weeds as well as burdock and dock species.
Wild carrot, hemp dogbane, common milkweed, and most brush species are less effective.
Milestone can be tank-mixed with other herbicides, and NIS is recommended to offer good control activity.
In addition, ForeFront R&P 3L contains 2,4-D to widen the spectrum of activity in the grass, hay, and pasture.
Forefront has a 7-day haying restriction against grazing animals and cattle, while Milestone has none.
Best Time To Spray Pasture Weeds?
Forage professionals advise spraying weeds when they are actively growing because pastures often contain a mix of weeds.
Treating knapweed, biennial thistles (musk or plumeless thistle), and perennial weeds like Canada thistle and leafy spurge early in the season or in the fall is also a good time.
Weed control applications made during drought or other factors inhibiting active growth of weed foliage may not reach the roots.
Whatever size your pasture is, the openness will unavoidably draw many an unwanted plant other than the grasses you want to maintain.
Depending on the season, specific times and other conditions are better to offer effective control of weeds.
Others, such as clover and grassy weeds, will be covered or blend in with your pasture grass.
Seasonal Applications
The best time to spray herbicide is weather dependent. Warm-season and cool-season weeds require different times.
The best times are before weeds germinate (pre-emergent) or after sprouting and vigorous growth (post-emergent).
Spraying for warm-season and cool-season weeds once a year will keep your fields free of volunteer growth.
Late winter
Pre-emergent herbicides in late winter prevent weed germination and allow grass to grow unimpeded when temperatures rise.
Early spring
The best time to use a post-emergent herbicide is in early spring, when annual and perennial weeds actively grow and absorb nutrients. While your warm-season grass emerges from dormancy, avoid spraying herbicide.
Late summer
Pre-emergent herbicide for cool-season weeds applied in late summer will, like early spring, prevent unwanted growth and allow your cool-season grass to grow without competition.
Early Fall
Post-emergent sprays should be made two weeks before the first frost; otherwise, weed control is impossible.
Frost-damaged leaf tissue won’t absorb formula well. However, damaging plants before the frost reduces their chances of surviving the winter.
Applying Herbicide
Read product labels and directions for detailed information on using a grass-safe weed killer herbicide like 24D, Tordon, or Milestone. (Find the Best Weed Killer With Pre-Emergent)
These formulae were made to be safe on certain grasses while targeting specific types of weeds before or after they emerge into active growth.
To have access to restricted products, you must first obtain a license for a private pesticide application. Education helps you understand how to apply the products safely and confidently.
When there is a chance of rain or if it is windy, spray herbicide should not be administered on wet grass. If it’s raining, the application will be diluted and may be washed away, and if it’s windy, the coverage will be uneven.
Weed Control Guidelines For Weeds in Pastures
You still have time if you couldn’t control winter annuals and biennials.
The timing of herbicide application (or mowing) differentiates between an effective strategy and a waste of time and money.
An herbicide application will be ineffective once the weeds have set seed. The seeds are likely to develop and germinate, such as winter annuals like yellow rocket, chickweed, marestail, annual bluegrass, etc. They are swiftly growing and flowering and setting seed.
The more wild carrot, the earlier, the better you treat biennials such as musk and plumeless thistle.
The optimum time to treat them is late fall or early spring.
Finally, control annual summer weeds soon as they emerge, when they are most susceptible to chemical control.
During this year, weed growth with common herbicides such as 2,4-D, triclopyr, and clopyralid are commonly used to control broadleaf weeds in grass hay/pasture.
In the spring, products containing metsulfuron can effectively control broadleaf weeds.
Inexperienced farmers should use caution when applying herbicides to newly seeded fodder grasses that have not yet been established. (Learn How Long Does Weed Killer Need Before Rain)
Here are some basic tips for managing some common weeds of pasture.
Winter annuals such as mustard, common chickweed, etc.
- To prevent seed production, mow after bolting.
- Before bolting, use an effective herbicide in the fall or spring.
- Most winter annuals bloom in late autumn, with a smaller number blooming in early spring.
- To prevent the transmission of disease, prevent seed production.
Summer annuals such as pigweed, common lambsquarters, ragweed, etc.
- Maintain a healthy and competitive land pasture.
- To prevent seed production, mow after bolting.
- In the early summer, use an effective herbicide.
- To prevent the transmission of disease, prevent seed production.
Biennials like common burdock, bull and musk thistle, poison hemlock, etc.
- To prevent seed production, mow after the plants have bolted before the seed set.
- Individual plants and roots should be removed or dug up by hand.
- In the spring or fall, spray rosettes with an effective herbicide.
- To prevent the transmission of disease, prevent seed production.
