Western Bean Cutworms moth #’s dropping — but look for larva

Contributed by Robert Moloney, NK Brand Seeds

Catches of Western Bean Cutworm (WBC) moths are rapidly dropping to zero across the province as of this week.  At this point we wouldn’t expect moths to be laying eggs anyway, but the overall catch numbers for the year give us an idea of how big and widespread the problem has the potential to become.  Even taking into account the fact that there were many more WBC moth traps in Ontario this year versus previous years, the number of moths caught increased massively this year.  We will have to wait for corn harvest to get a better handle on just what this means for the damage we may see in Ontario this year, but it isn’t difficult to find larva in corn ears in areas with high moth capture numbers now (see previous blog entries for details on scouting for larva).  The larvae are very mobile, so even if you couldn’t find the low numbers of egg masses in the field earlier, you may be able to find the larva and damage now.  In plots at the NK Arva research station which had egg masses moved into them to ensure infestation of WBC it is not uncommon to find larva in every cob within 6-8 feet of row from the marked plant that the egg mass was attached to.  In some spots they have moved even farther than this.  The positive news is that plants with the Agrisure Viptera 3111 trait that also had egg masses attached to them are showing no signs of WBC damage or larva survival.

Why scout for larva?

At this point in the season we can’t do anything to control the WBC larva in the cob but it is still worth scouting your fields to get an idea of what level of WBC larva pressure you have in the field.  This will allow you to prioritize fields with higher potential for ear mould growth for earlier harvest.  In some fields we are already seeing some ear mould development where WBC have been feeding.

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