weather
Mary Lou Peter-Blecha
K-State Research & Extension News
2/15/2006, 10:49 AM CST
Construction crews, kids at recess ... anyone who spends time outdoors has likely enjoyed this winter's mild weather, but wheat growers should be wary, a Kansas State University agronomist said.
"Wheat in many areas greened up in January and can no longer be considered dormant," said Jim Shroyer, agronomy state leader with K-State Research and Extension. "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, Shroyer said. 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, he said. 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.
The fact that temperatures in early February were somewhat cooler than in January may help wheat regain some of its winter-hardiness, the agronomist said.
Finally, warm weather in January and 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 said. Early-season diseases include powdery mildew and tan spot.
"One factor that is not a concern is vernalization," the agronomist said. "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 degrees, that's enough to vernalize any of the current winter wheat varieties commonly grown in Kansas. We've already had that."
Shroyer said that during warm winters, producers often ask whether the wheat will start jointing in February.
"That's unlikely, but possible," he said. "I don't know of any wheat that has jointed yet in Kansas. But if temperatures remain warm, some of the earliest varieties, such as Jagger, could start jointing early. Wheat that joints early is more vulnerable to spring freeze injury."
Shroyer is suggesting that producers watch their wheat crops for insects, diseases, and the weather in February and March. 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.
Mary Lou Peter-Blecha
K-State Research & Extension News
2/15/2006, 10:49 AM CST
Construction crews, kids at recess ... anyone who spends time outdoors has likely enjoyed this winter's mild weather, but wheat growers should be wary, a Kansas State University agronomist said.
"Wheat in many areas greened up in January and can no longer be considered dormant," said Jim Shroyer, agronomy state leader with K-State Research and Extension. "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, Shroyer said. 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, he said. 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.
The fact that temperatures in early February were somewhat cooler than in January may help wheat regain some of its winter-hardiness, the agronomist said.
Finally, warm weather in January and 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 said. Early-season diseases include powdery mildew and tan spot.
"One factor that is not a concern is vernalization," the agronomist said. "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 degrees, that's enough to vernalize any of the current winter wheat varieties commonly grown in Kansas. We've already had that."
Shroyer said that during warm winters, producers often ask whether the wheat will start jointing in February.
"That's unlikely, but possible," he said. "I don't know of any wheat that has jointed yet in Kansas. But if temperatures remain warm, some of the earliest varieties, such as Jagger, could start jointing early. Wheat that joints early is more vulnerable to spring freeze injury."
Shroyer is suggesting that producers watch their wheat crops for insects, diseases, and the weather in February and March. 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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