Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
4/28/04
Contact:
Robert Hartzler, Agronomy, (516) 294-1923, hartzler@iastate.edu
Rachel E. Martin, Iowa Beef Center, (515) 294-9124, remartin@iastate.edu
AMES, Iowa--Spring is a busy time in Iowa, and many beef producers put off pasture weed management until summer months when there’s more time to tackle the problem. However, the months of May and June are best for addressing many pasture problem areas.
Rather than beginning with targeting weeds, producers should focus their efforts on taking care of the pasture forage, says Bob Hartzler, weed specialist, Iowa State University. “The number one weed control tool is a competitive sod. Proper fertilization, grazing management and appropriate species selection will prevent 99 percent of weeds from getting established in the pasture,” he notes.
Even with proper pasture management, some weeds can still invade the paddock. Often it is stubborn biennial or perennial thistles, which grow easily as cattle avoid the spiny plants.
Biennial species, such as bull and musk thistle, present the biggest challenge, according to Hartzler. An early spring herbicide application is essential during the plant’s rosette stage, prior to the plant sending up its flower stalk. At that point, the plant becomes very difficult to kill. Hartzler adds, “Producers can get a jump on biennial thistles by spraying in the fall of the first year of their growth.”
A perennial species, such as Canada thistle, presents different challenges. Unlike biennial thistles, which propagate only through seeds, Canada thistle reproduces by an extensive and durable root system as well as seed. Contrary to biennial control, Hartzler recommends that herbicide treatment be delayed until June or July when the Canada thistle starts to flower. “Persistance is the key to controlling perennial weeds, since it is difficult to kill the root system with a single application. Products containing picloram, such as Grazon® P&D, provide the most consistent control of Canada thistle,” he advises.
Annual species such as plants like pigweed or lambsquarter don’t
represent a real threat in and of themselves, but can indicate the need for
better forage
management. “While it’s often our knee-jerk reaction to use a quick
fix like herbicides, producers should investigate what allowed the weed to
invade the pasture in the first place, such as overstocking of livestock, and
take steps to correct the situation,” Hartzler says.
For more information on pasture weed management, contact Bob Hartzler at (515)
294-1923 or hartzler@iastate.edu.
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