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09
May
2013
Insects are in the wheat crop but don’t get excited just yet
Author: Gus Lorenz, Extension Entomologist

I guess it got dry enough to walk some fields today. My phone was ringing off the wall with calls, mostly about stink bugs in wheat.  Everyone is seeing stink bugs, so what do we need to do about the situation?  From what we can tell by our observations and the folks we are talking to, it appears to be mostly rice stink bugs. There’s an occasional brown stink bug or sometimes a rare green stink bug, but mostly they are rice stink bugs.  We are seeing fairly noticeable numbers of these stink bugs, but I haven’t seen or heard from anyone of any levels that I considered worth spraying.  The accepted threshold (as I’ve been told—there’s not one in the MP-144) for most of us in the Midsouth is one stinkbug per 5-10 heads while wheat is in the milk to soft dough stage.  Most of our wheat appears to be in the soft dough stage.  When you see a lot of stink bugs at bloom going into milk stage it’s time to be concerned about stink bugs.  Once you get into the hard dough stage, a stink bug can’t damage the kernel.  One stink bug every 5 to 10 heads isn’t a bunch of stink bugs, so don’t get too excited.

greenstinkbug

Green stink bug

brownstinkbug

Brown stink bug

Rice stink bug

Rice stink bug

 

 

 

 

 

 

 

 

You may notice when scouting wheat fields for stink bug that you find the highest numbers on the edges of the field, particularly near levees, tree lines, CRP, pastures, etc. As you move into the field the numbers should drop off tremendously.  So, on the off chance you do have to spray, you can probably limit your applications to the borders of the field.  One to two (at the most) passes should do the job.

I’m also getting a few calls on armyworms in wheat;  it’s the true armyworm, which are not unusual in the wheat crop this time of year. The difference this year is they are still small and haven’t moved up the plant at all, one of the few advantages of a cold spring I guess.  Based on our observations and calls received, for the most part the armyworms are about an 1/8-1/4” long and are staying low in the canopy.  Most of the numbers appear to be about 1-2 up to 4-5 per square foot.  We have seen no movement up to the flag leaf anywhere at this point.  Believe it or not, I’m hearing that a few people are spraying—although I don’t know why.  With most wheat already in soft dough, that’s a losing proposition.  Once you reach soft dough and they aren’t cutting heads, you are making money by not spraying.  We worked hard on that threshold, and I have every confidence that yields are maintained once the wheat reaches soft dough, even if they eat the flag leaf.  Populations hitting earlier, like at bloom or milk stage, might cause yield loss but at the soft dough stage, where most wheat is right now, we should be fine.  That is, UNLESS, the armyworms start cutting heads. Then we need to take action.  Same as with stink bugs, if you have to spray, pyrethroids will probably be the product of choice. Always read and follow the label.

truearmyworm

True armyworm

I guess the gist of all this is scout closely and don’t get caught up in thinking you need to spray because there are a few pests out there.


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