Grass forages and pastures

Part 2, Section 6: Forages Pest Management

Forages Pest Management

WEEDS

Grass forages and pastures

Without proper management, broadleaf weeds can directly compete with forage grasses or pasture to reduce their nutritional value and longevity. Weeds can replace desirable grass species, filling in gaps or voids and reducing yield and overall quality of the hay or pasture. In addition, certain plants such as poison hemlock, white snakeroot, or black locust have toxic properties that can cause livestock injury or loss under certain circumstances.

Biennial and perennial weeds are probably the biggest weed problems for grass hay and pasture producers. Both biennials and perennials produce seed each year, potentially starting new infestations. In addition, perennial weeds such as hemp dogbane, Canada thistle, and multiflora rose reproduce from underground roots or rhizomes. Perennial rooting structures can survive for several years in the soil and are often unaffected by occasional mowing or livestock grazing.

Good cultural practices, including maintaining optimum soil fertility, using a competitive cutting schedule for grass forages, and rotational grazing and periodic mowing in grass pastures, can help keep a crop competitive with weeds. The most critical time for weed control is during the establishment year. If a no-till seeding is desired, be sure the preplant vegetation is adequately controlled. See Table 2.6-2 for the relative effectiveness of Gramoxone Extra or Roundup/glyphosate in controlling preplant vegetation.

In general, use preplant tillage or herbicides, companion seedings, mowing, and/or a postemergence herbicide to ensure that weeds are not a problem that seedling year. To reduce weed shading, mow at a height above the grass seedlings when weeds are 8 to 10 inches tall. For warm-season grasses, do not mow after early August.

Several herbicides are labeled for broadleaf weed control in grass forages and pastures. But not all pasture herbicides allow cutting the grass for hay, and most herbicides have grazing restrictions. See Tables 2.6-7 through 2.6-9 for specific information about grass forage and pasture herbicide effectiveness, use, and grazing and haying restrictions.