Control in an established stand

Part 2, Section 6: Forages Pest Management

Forages Pest Management

WEEDS

Legumes

Control in an established stand

The best weed control in an established forage stand is achieved by maintaining a dense healthy stand through proper fertilization, cutting management, and insect control. Controlling weeds in established forages is normally of greatest benefit in the first cutting. Weeds generally contribute much less to yield in the second and succeeding harvests. Before using an herbicide in established stands, evaluate the forage to ensure it is worth the cost of the herbicide.

Below are some general rules to follow before using an herbicide in established forage stands:

• Thin or irregular stands do not thicken once weeds are removed. Be sure there are sufficient desirable species to fill in the gaps. A minimum of five alfalfa plants per square foot should be present.
• Weeds tolerant of the herbicide may invade the space left by susceptible species, ultimately creating a more severe weed problem.
• Treat only well-established, vigorous stands with herbicides.
• If the forage stand is at least two years old and 25 percent to 30 percent of the plants are weeds, removing them with an herbicide application is of questionable value.
• If 50 percent or more of the plants are weeds, it is time to rotate to a different crop.

If weeds become a problem in established forages, several herbicide options are available (see Table 2.6-5). Chemical control in established forage legumes is often limited to late fall or early spring applications. Also, many products have harvesting, feeding, or grazing restrictions on their use. See Table 2.6-6 for these restrictions.