Air April 27, 2005

Thank you Jerry, and good morning everyone. Early indications are that cooler weather have slowed down the alfalfa weevils more than the alfalfa so that bodes well towards not having to make a second spraying on some of these fields! Of course the big news on many folks mind was the cold weather over the weekend and what effect that will have on the rapidly developing wheat crop.

Of course, the question this week is whether the cold temperatures over the weekend damaged any of the wheat. Unfortunately, that is going to be very very hard to say with any certainty for sometime. There may be some low areas that collected some frost that will be showing some obvious damage any time now. Once wheat has started jointing, it's already lost a lot of its cold tolerance and will continue to lose cold tolerance. Keep in mind that a brief dip in temperature won't cause that much damage, we are generally concerned about 2 or more hours at a certain temperature. And naturally, the colder it gets the more severe and widespread the damage becomes. At jointing, 24 degrees is where the damage begins. By the time you get to boot, that minimum temperature is up to 28 degrees. The coldest temperatures at the Milford Lake corps office over the weekend was 32 degrees. The Manhattan airport, a notorious cold spot, got down to 26, maybe 25. Most of the wheat is just a little ahead of boot so the critical temperature is probably 26 to 27 degrees. So somewhere in between 26 and 32 is where the temperatures probably have fallen in recent mornings. We also all know that cold air drifts into and collects in lower lying areas, so we can expect to see more damage in those spots. Most of the damage that may have occurred is not going to be visible until heading or after. Light freeze damage shows up as sterile heads or sterile spots on heads. Moderate damage adds the possibility of heads that emerge kinked or trapped in the boot. And more severe freeze damage will result in death of the head and other plant tissue. If this has happened you should be able to walk out into fields and literally smell the damage as plants start to decay. Most fields should have received little if any damage, but some fields will turn up at harvest with poor yields from the free damage.

This is Chuck Otte, Geary County Extension Agent, with Ag Outlook 2005.

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