Fall Weeds on Rise

Consultant warns farmers to ready to tackle tough weeds with fall applications.

Published on: Nov 16, 2007

Dry weather followed by early fall rains flooded fields with weeds in Ohio and other parts of the Eastern Corn Belt. "Farmers reported more lambsquarter, velvetleaf and foxtail problems late," says Geoff Trainer, Seed Consultants, Inc. research agronomist in Mt. Gilead. "There's potential that more seed will be added to the weed bank."

Now is a good time to make herbicide applications to prevent weeds from sprouting and becoming a problem in the spring. Winter annuals such as chickweed, henbit and purple deadnettle are particularly menacing. Purple deadnettle is a host carrier for Soybean Cyst Nematod. SCN costs soybean growers up to $1 billion in yield loss every year, according to the University of Missouri.

The winter annuals also creep across fields and cause headaches for no tillers. "The weeds don't allow the soils to dry out and warm up for no-till planting in the spring," Trainer points out.

Geoff Trainer Seed Consultants, Inc. agronomist explains weed control options at the Southwestern Ohio Corn Growers field day. Fall herbicide applications work well for dandelion and Canada thistle.

Along with spreading the workload, fall applications work better for some weeds such as dandelion and Canadian thistle. Ohio State University research shows a minimum of a minimum of 1 pint per acre of 2,4-D in corn or soybean stubble offers the best control for Canada thistle. For dandelions make the applications after the first frost, but when nighttime temperatures are not below 40 degrees F.

Fall applications should be made at least a week after harvest to allow the weeds to re-grow. The best control is obtained while the weeds are still green—before mid-November. The cost of fall treatments should not exceed $6 to $12 per acre, excluding application.

Watch for chances to make fall applications. Few fall applications were made in '06 because of wet weather. "There may be a short window of opportunity. "You can get some control--vs. not being able to get into the field and having the weeds get bigger and harder to control," Trainer says.