Concerns about Smooth Bedstraw

There has been more than one farmer interested in learning more about smooth bedstraw this spring.  This unpalatable weed can be very invasive, and it reproduces relatively early.  Some interesting facts that can help you manage this weed include:

  • The seeds are viable even when they are still green
  • The seeds are only viable in the soil for about a year
  • When conditions are wet, the seeds are likely to cling to your equipment and can easily be spread to other fields
  • Weeds in general will encroach on areas where forage plants are not competitive, often due to sub-optimal soil fertility, compaction, or poor species/variety selection.
  • Any herbicide that kills smooth bedstraw will also kill your legumes
  • It has begun to flower

My purpose here is to discuss some alternatives for reducing the presence of this weed in your hay field or pasture, short of starting over altogether.

Smooth bedstraw in a pasture

Organic farmers and others preferring not to use herbicides will have to focus on using harvest management to reduce seed production and also not neglect to discover underlying agronomic issues that allowed the smooth bedstraw to take hold.  These farmers will also need to find ways to re-introduce forage species in places where they have been crowded out by weeds.  To reduce the number of smooth bedstraw seeds produced this year, forage needs to be harvested even before the green seeds are formed on the smooth bedstraw plants.  Harvesting will help, but will not entirely prevent seed production for all plants, because some of the plants will already have viable seeds by the time things dry out enough to harvest, and others may be prostrate enough not to be picked up by harvesting equipment.

If you are not organic and don’t mind losing all of the legumes in your pasture or hay field for a while, you have the option of using herbicides.  Literature from University of Maine Extension suggests that triclopyr-containing herbicides labeled for use on pastures and hay fields, such as Crossbow, or aminopyralid containing herbicides, such as Milestone or Forefront RP, are effective against smooth bedstraw. Applying one of these herbicides prior to seed being produced in the spring and another in August/September should vastly reduce the amount of smooth bedstraw in your stand next year.  If you are only able to make a late-summer or early-fall application, you will still have spring-produced smooth bedstraw seed to contend with next year due to the longevity (about one year) of the seeds produced this year.

Keep in mind, this weed took hold because it had an opportunity.  Now is the time to figure out if it is compaction, poor soil fertility, or some other agronomic problem.  If the problem is not fixed, you can expect smooth bedstraw (or worse) to visit your pasture or hay field again.  If the plants produce seed this year, the problem will almost certainly be present next year.  Please understand that all of the herbicides mentioned above will kill your legumes and many other broadleaf weeds (and other broadleaf plants if the herbicide drifts!).  Pay close attention to harvest restrictions. The aminopyralid herbicides can be persistent and the label says the manure from animals consuming forages from fields to which aminopyralid has been applied should not be spread in areas where broadleaf vegetables will be planted. They also say that a ‘bioassay’ should be conducted prior to trying to re-establish legumes.  One way to do this is to go out in March (or so) and get some soil from the field to which the aminopyralid was applied the previous season.  Bring it inside, and sprinkle some red clover seeds on it, covering them lightly with soil.  Keep the soil moist, at about room temperature, and in a well-lit area so the seeds will germinate, emerge, and begin to develop.   For comparison, the same process should be done using soil from a field not sprayed with the aminopyralid herbicide. If both batches of clover seedlings seem to get going well enough, consider frost-seeding or no-tilling clover into the existing grasses to increase the legume content of the stand and to fill in the gaps. I only suggest using this type of “soil bioassay” because the label does specify what kind of ‘bio-assay’ they have in mind; this would seem to fulfill the letter (if not the spirit) of what they are suggesting.

To give you an idea of the cost of these herbicides one local farm service provider recently indicated that Crossbow was $53/gallon and Forefront was $64.50/gallon.  The labels suggest Crossbow be applied at 2 quarts per acre, and Forefront at 1.5 – 2.6 pints per acre. Always read and follow the label and take special note of harvest/grazing restrictions, which are from 0 to 14 days, depending on the product, harvest method, and class of livestock to which it will be fed.  The labels for the products discussed can be found at:
Milestone: http://www.cdms.net/LDat/ld77N009.pdf
Forefront:
http://www.cdms.net/LDat/ld7IE007.pdf
Crossbow:
http://www.cdms.net/LDat/ld02H006.pdf

It is not the intention of the author or University of Vermont Extension to endorse or promote the use of any product over another.


References:

Seiter, Stefan, 2003.  Managing Smooth Bedstraw in Forage Crops.  University of New Hampshire Extension. Online: http://ceinfo.unh.edu/Pubs/AgPubs/bdstrw.pdf.

Kersbergen, Richard, 2008. Bulletin #2778: Controlling Smooth Bedstraw in Hayfields and Pastures.  University of Maine Extension.  Online: http://umaine.edu/publications/2278e/

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