Western Bean Cutworm and Beans This Week

Based on scouting observations and trap counts so far, it looks like we have finally passed the peak for western bean cutworm moth activity.  Egg masses are difficult to find now in corn which tells us that the moths are no longer interested in laying eggs in that crop…unless of course there is an extremely late planted corn field in the area.  Then those fields could still be at risk.

But for the most part, scouting needs to focus on the bean crop now.  Do not spray fields based on moth catches or egg masses.  Wait until you see pod feeding by WBC so that you are targeting the larvae that are actually doing the damage.  It will result in much more effective control.  There was a CropPest newsletter article that went out last week with some of my previous blog entries but also has a good picture of what early pod feeding looks like by Chris Difonzo. Click here to see the article and the photo.

Again Matador is registered for the bean crop and Matador and Decis are registered for the corn crop.  No other products are registered for control of western bean cutworm at this time.  We do have permission from CFIA to spray the refuge with insecticide if it reaches threshold for western bean cutworm, as long as the adjacent Bt corn field is also sprayed at the same time.

6 thoughts on “Western Bean Cutworm and Beans This Week

  1. Tracey, lots of good work on the collecting and displaying the WCB data. Well done!
    When I was talking to a producer yesterday he mentioned cumulative count numbers when trying to assess if he should be spraying. Your blog mentions recs based on peak numbers. I think that the cumulative maps are nice to summarize the area counts but appear to be confusing some people…we are all learning on this one.


    1. Hi Walt

      This is a learning curve for all of us. The traps are only there to tell us that moths are present in the area. Watching for peak flight tells us when peak egg laying is too so we know when to be in the fields looking for eggs.

      The most important thing we learned this year is that moths are very particular in which fields they lay their eggs in. You can not base management decisions on moth numbers since yes, your trap at your field could be catching lots but the actual moths may not be going into your field because it is not at the right stage for them. Spraying based on moth counts is not accurate at all.

  2. Tracey – we suspect we’re seeing WBC larva feedinng on seed corn silk and boring into the cobs – will Matador control it if we catch it early enough?

    1. If you are still finding them on the silks there is a chance that a spray focused on the ears may control them, especially since seed corn is shorter and easier to reach the ears with the sprayer. But I can not guarantee good control since some could be in the ears already.

      Seed corn may need its own management guidelines in the future since in field corn we would target the top of the plant and tassel to spray the young larvae. With the tassel pulled, I assume you control some when it is detasseled but at the same time it forces the rest of the larvae to move down to the ear instead.

  3. Hi Tracy! I work with dry bean growers in New York State but members of our Extension team work on processing snap beans. Has WBC damage been found in snap beans? We have seen egg masses on sweet corn. Thanks! Carol

    1. Hi Carol

      Great to see that my blog is being read in NY! Yes they can feed on snap beans and sweet corn. I actually suspect that late planted sweet corn could be just as at risk now as the bean crop is. I have not see any feeding myself on either sweet corn or snaps as I have only focused on field corn and dry bean fields but I will ask the vegetable specialist and see if she has been finding anything.

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