Weed resistance becoming a problem in Southeast wheat crop

The Carolinas and Virginia planted an extra 250,000 acres of wheat this past fall, compared to the fall of 2011 to take advantage of continued good prices for wheat and reflective of continued high prices for soybeans that can be planted in a double-crop/double-value economic scenario.

Getting wheat planted in the fall came with a few hitches, starting with finding enough seed in the desired varieties. Less than optimum seed supplies in the fall could have some yield-limiting consequences when wheat is harvested during May and June in the region.

Virginia Tech Small Grains Specialist Wade Thomason says seed size on some of the more popular varieties may contribute to thin stands and increase the chances of yield loss to a number of pests this year.

“Getting a good stand with the optimum number of plants per acre is an important part of achieving high wheat yields. A large amount of research in Virginia and the mid-Atlantic region supports the statement that we need about 25 vigorous seedlings per square foot in the fall to achieve these high yields. Since germination and emergence are not 100 percent, we recommend seeding at 30-35 seeds per square foot,” Thomason says.

Wheat growers in Virginia have been coping with weed resistance in hard-to-manage chickweed and other small-seeded weeds for the past couple of years.

ALS-inhibiting herbicides, (such as Harmony Extra, Osprey, and PowerFlex), have been used for the past several years to manage these weed problems, but those days of spray and go are rapidly going away.

In 2009, Virginia Tech Agronomist Scott Hagood first noted the problem in Virginia wheat. “In terms of plant weight, using .5 up to 32 times the labeled rate of Harmony GT we saw 98 percent or better control of the wild chickweed. On two samples from grower fields back in 2009, the best we could get was 50 percent control and on some of these plants we got virtually no control,” Hagood says.

Read the rest of the story at Southeast Farm Press.

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