Air March 29, 2000

Thank you Mark, and good morning everyone. March is almost gone, April’s coming on fast, the weather feels like spring and the alfalfa is growing. The good news is that we’ve had some pretty good precipitation the last 6 weeks so I’m optimistic, for the time being. The bad news is that alfalfa weevil, and other problems, are showing up in the wheat that need to be discussed. First a few thoughts about pasture burning. It’s too too early to be burning native grass pastures. Sure, it’s been warm, and the rain has a lot of things greening up. But it is still too early to burn. If you have a serious disagreement with that, give me a call and we’ll have a dandy discussion.

I’ve had some calls about yellow and brown patches in wheat. The good news is that we don’t need to be spraying aphids. While I’ve found some aphids and greenbugs in the wheat, the numbers are still pretty low. Off color patches in the wheat, that I’ve found, have been one of two things. Tan spot was scattered about the area last fall and is still fairly common. By far the bigger problem has been Barley Yellow Dwarf. This will cause yellow spots in fields and on closer examination those yellow leaves will often have a purple or red tint to the leaf tip. This is an aphid borne viral disease and these areas were infected last fall. The problem is going to be worst in the earliest planted wheat that was the lushest last fall, because this is where the aphids would have been found. In either case, there is nothing that can be done right now. Fall infection from Barley Yellow Dwarf can result in yield losses of over 30%. You can also expect to see these fields be very ragged and uneven looking through the rest of the season.

I’ve been finding Alfalfa Weevil larvae for a couple weeks now. Small alfalfa is going to be more susceptible to damage, but we don’t want to get in a hurry to spray as we still have eggs hatching out and perhaps even some spring egg laying going on. If the alfalfa averages 5 inches in height, and with the current value of alfalfa being about 50 - 70 dollars per ton, treatment levels are about 1 larva per stem. That treatment level jumps up to 2 per stem when the alfalfa is about 14 inches tall. Failure to treat in a timely fashion will hurt yield all summer long. Treating too soon will cause added expense from needing to retreat. The key is to get out of the pickup to check the alfalfa. When you can see the damage from the road, you’ve already missed the important treatment threshold and your yields will suffer the rest of the year.

This is Chuck Otte, Geary County Extension Agent, with Ag Outlook 2000.

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