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Early Greening Could Spawn Early Disease And Insect Pressure


As a wheat farmer, Jay Cook says it's good to see sprouts emerging from his fields near Garden City, KS. He would have preferred, however, to see them shortly after he planted his wheat last October.

Cook is like many southern plains producers who have seen unseasonably warm temperatures after the Arctic blast that dumped a lot of needed snow over many drying fields. The warm air brought some wheat out of dormancy and threatens overall growth. "I have a 6-ft. profile of moisture under the seeded wheat, so I don't think moisture will be a problem. But a poor stand and not enough tillers will limit the yield," says Cook, who surveyed his fields Feb. 16, after the frost had left the ground and wheat had broken dormancy.

Jim Shroyer, agronomy state leader with K-State Research and Extension, says the fact that the 2011 wheat crop is emerging from a cold winter's nap this early in the year is a bit of a concern. "In many areas of Kansas, wheat has greened up and can no longer be considered dormant," Shroyer says. "Some growth may be taking place, especially where moisture conditions are good and daytime highs have been in the 60s or 70s."

That may make wheat look good for this time of year, but it would be much better if temperatures were colder, he adds. For several reasons, record-high temperatures in winter are not good for wheat. Plants growing at this time of year use valuable soil moisture. Where topsoil is dry, this puts added stress on wheat plants. Even where topsoil moisture is adequate, it would be better used later in the growing season.

In addition, plants will have lost some of their winter hardiness, says Shroyer, adding that this won't be a problem if the weather never turns extremely cold again this winter or if temperatures cool down gradually, so the plants can regain some of their winter hardiness. If the wheat is green and growing, however, and temperatures suddenly go from unusually warm to extremely cold, either winterkill or spring freeze injury could occur.

Disease and insect concerns

Warm weather in February could spark insect and disease problems earlier than normal. Army cutworms are sometimes a problem in wheat fields during February and March. Other early spring insects to watch include winter grain mites and greenbugs, Shroyer points out. Early season diseases include powdery mildew and tan spot.

"One factor that is not a concern is vernalization," he says. "The vernalization requirement of winter wheat is more of a 'cool' requirement than a 'cold' requirement. Varieties have different vernalization requirements, but so long as there are three to five weeks in which the air temperature is below 48° F, that's enough to vernalize any of the current winter wheat varieties commonly grown in Kansas (and the High Plains). We've already had that."

Shroyer suggests farmers watch their wheat crops for insects, diseases and the weather in February and March, noting that the longer temperatures remain above normal, the less winter hardiness wheat will have and the more susceptible it will be to a sudden temperature drop to the single digits or below. 

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