Image source: Bill Johnson
- Weeds are generally lower in feed quality, both crude protein and digestibility, particularly as they mature.
- Some weeds can be toxic to livestock. Toxicity is generally not an issue unless there is little else for the cattle to eat. Some weeds are not palatable due to thorns, bristles or hairs on the leaves and stems.
- There are no threshold numbers for weed management. As pastures mature and become overgrazed, weeds will infest the bare areas. Proper management of soil pH, fertility levels, and grazing management, along with properly timed herbicide applications keep pastures productive.
Weeds are prominent this year in many grass pastures. Late May to Early June is the best time to control many perennials, annuals, and woody plants. It is also important to remember that it's usually better to spray too early than too late.
Winter annuals including buttercups, mustards, chickweeds, marestail, deadnettle/henbit, fleabane, and others are growing rapidly and will begin to flower and set seed very soon. Biennials including poison hemlock, biennial thistles, burdock, wild carrot, etc. should be treated before they begin to bolt. Management of perennial weeds such as stinging nettles, dandelion, Canada thistle, ironweed, and the woody perennials such as multiflora rose, honeysuckle, autumn olive, and locust is best in early summer after plants reach the bud-to-bloom stage.
The most common herbicides used for control of many broadleaf weeds in grass hay/pasture this time of year are growth regulator herbicides such as 2,4-D (Radar®) ± dicamba (Clarity®, etc.), triclopyr products (Crossbow, Remedy Ultra, etc.), picloram (Tordon, Grazon P + D), aminopyralid (Grazon Next HL®, Chaparral®), and clopyralid (Stinger®, Curtail®, PastureGard®, etc.). In most situations, a tankmix of 2,4-D (1 quart/acre) plus dicamba (1 pint/acre) usually does a good job on annual broadleaf weeds. However, there are certain weeds where other herbicides will be necessary for optimal control and at a different time of year. For biennial thistles and poison hemlock, herbicides that contain aminopyralid work well. For herbaceous perennials, products that have triclopyr, picloram, metsulfuron, and aminopyralid work well. For woody perennials, products that have triclopyr and metsulfuron in them work well. For more specific information consult the weed efficacy tables in the pasture section of the FS Crop Protection Handbook for specific details on individual weeds. Also, there are grazing restrictions following the use of some herbicides, so read and follow all label directions and consult with your FS Crop Specialist if you have questions.