Jerry Lamp tried fall herbicide applications for the first time in '99, and he'll do it again this year. The payoff: It saves time and field trips in spring, he says.
Lamp, of Lancaster, OH, farms 3,100 acres with his dad, Wilber, brother Tom, and nephews Rich and Rob. Almost all of their acreage is no-till.
Conditions were ideal for fall application last year - a harvest finished by Halloween, warm temperatures and healthy weeds. "The thistles were growing well," says Lamp.
Along with Canada thistle, Lamp targeted chickweed, deadnettle, henbit and winter annuals that are tough to control in spring.
In early November, Lamp applied 6 oz of Sencor and 1 pint of 2,4-D per acre to 300 acres of cornstalks. The fields were planted to Roundup Ready soybeans last spring.
In one field, Lamp didn't need to apply any spring herbicides after the fall application. And he was able to reduce burndown herbicides on about a third of the fall-applied acres.
November is the best time to control winter annuals, with either tillage or herbicides, says Mark Loux, Ohio State University extension herbicide specialist.
"Weeds are smaller and more susceptible to herbicides in the fall, and the weather may be more conducive for herbicide activity," he says.
In 1999, Loux found that the most effective tankmixes against winter annuals were Sencor or Gramoxone plus 2,4-D when weeds were small; glyphosate plus 2,4-D when weeds were more than a few inches tall.
The main disadvantage of fall applications, says Bob Hartzler, Iowa State University weed control specialist, is the potential for late-season weed escapes caused by early breakdown of the herbicide. Although degradation is slowed by cold soils during winter and early spring, losses can be significant, Hartzler says.
Here's Iowa State's list of restrictions for fall-applied herbicides intended for pre-emergence control the following spring. See herbicide labels for complete instructions and restrictions.
Axiom - Apply after Oct. 15 when the sustained soil temperature at the 4" depth is less than 50ø, but before the ground is frozen. Apply only to medium- and fine-textured soils with 2.5% or greater organic matter.
Degree - Apply to soybean stubble after Oct. 15 when the sustained soil temperature at the 4" depth is less than 50ø, but before the ground freezes. Apply only to medium- and fine-textured soils with 2.5% or greater organic matter.
Dual II Magnum - Apply after Sept. 30 north of Route 30 and after Oct. 15 south of Route 30. Sustained soil temperature at the 4" depth must be less than 55ø and falling. Do not apply to frozen soil.
Frontier - Apply after Oct. 1 when soil temperatures 4" deep are sustained at less than 55ø and before the ground freezes. Apply only to medium- and fine-textured soils with 2.5% or greater organic matter.