Many beef and small ruminant producers are looking forward to pastures greening up in Wisconsin. In some pastures that will include troublesome weeds. Management timing for weed control is narrow for some species and can be the difference between success and a waste of time and money. Here are some helpful hints for spring pasture weed control.
Management timing plays a key role in weed control success
Control winter annuals before flowering
Winter annuals including yellow rockets and many other mustard species (common chickweed, marestail, fleabane, etc.) germinate in the fall and they will rapidly grow with a little sunlight and heat. For good weed control, target management prior to flowering, as once they begin setting seed management will not be as effective, and some of the seeds will develop and become viable.
Control biennials before the stem appears
Biennials including bull, musk and plumeless thistle, burdock, wild parsnip and wild carrot, etc. should be controlled while they are still rosettes (before a stem appears). This will prevent losses in forage from competition. While they can be controlled later when bolting/flowering, desirable forage can be lost due to competition, and management will require more time/resources. Late fall or early spring is the best time will have the best outcome.
Options for controlling annuals and biennials in pastures
Herbicides for spring weed control
Follow label directions every time you use herbicides. If the pasture was recently seeded, pay particular attention to restrictions on use after seeding. Some products that are safe on established forage species may cause injury to recently planted forage species. Nearly all herbicides registered for use in pastures will injure/remove legumes from pastures. It is also important to review the herbicide’s grazing and harvest restrictions. Those restrictions should be a factor in selecting the best herbicide to meet farm needs. Spot spraying can be a more economical option if weeds are only found in small areas of the pasture.
Mowing/ clipping for controlling annuals and biennials
Timing is critical with mowing. While timing is species-specific, in general, mow after the weeds bolt (grow the taller stalk) but before they produce seed. This timing range can be short (< two weeks) with some species, and if done too early, repeated mowing will be required. If mowed too late, viable seeds will be produced and spread by the activity.
If the weeds are not too dense or too numerous, digging is also a method for controlling them. Biennial thistles are an example of a weed that may be dug out as long if they are not too thick. They can be dug or snapped off below ground once they bolt, but before they flower to prevent seed production.
Manage soil fertility to create an optimal environment for desired species to grow
Killing weeds is just one part of weed management in pastures. If we do not do anything to encourage desirable species to grow after killing the weeds in those problem areas, then we will most likely just get a new crop of weeds. Soil fertility problems are one reason why some areas in the pasture are more prone to weeds than desirable species. Overgrazing or hardpans from livestock traffic may also contribute to conditions not favorable for the growth of desired species. Soil testing to determine any nutrient management needs and evaluate past management practices to identify corrections needed to encourage desirable species to grow.
In summary, there are opportunities for spring pasture weed management, but timing is critical to their success. It is also important to follow up weed control by implementing a plan to encourage desirable species to grow in those areas after the weeds are controlled, or the weeds will return.