WBC Eggs Found in Fields in Ontario

WBC eggs found in corn field in Norfolk County (T. Baute, OMAFRA)I was starting to doubt my abilities to properly scout for WBC eggs, given my height.  I walked a lot of fields last year with zero success.   I was really good at finding larvae in the fall though so clearly there were eggs to be found earlier that year.  You start to feel somewhat of a hypocrite when you haven’t actually found eggs yourself and you have to tell people “how to scout for them”.

But yesterday I received word that Mike Russell, a Cargill scout, had found WBC eggs in a few fields in Norfolk County.  Desperate as we are to find eggs for research trials at Ridgetown, I quickly drove to find him.  Not only did he direct me to the field but Mike already had 10 egg masses in hand to pass on to me.  Nice job!  Going to the field myself, within a few minutes I FOUND EGGS MYSELF, making me feel much better about being so vertically challenged.   Since then, my students have also found eggs at a field in Strathroy.

Going back to the field today, I have learned a bit more about how to scout for WBC eggs and I also got a few cool pics too.

First, CROP STAGE:  It really does come down to which field is in the ideal crop stage for the moth.  They really do like to lay their eggs on plants that are not in tassel.  This particular field was already in tassel but some of the plants within the large headland were shorter and were not quite in tassel yet.  When we scouted the rest of the field and neighbouring ones that were in full tassel, eggs were not nearly as easy to find.  Even if a trap located within a corn field has caught a bunch of moths, the moths may not have selected that particular field to lay the eggs.  They are likely to look around and pick the one nearby that has not tasseled yet.  Or at the very least, has some plants less advanced than the rest of the field.


Sun Shining Through Leaf to Show Shadow of WBC Egg (T. Baute,  OMAFRA)
Sun Shining Through Leaf to Show Shadow of WBC Egg (T. Baute, OMAFRA)
Egg mass that was making the shadow (T. Baute, OMAFRA)
Egg mass that was making the shadow (T. Baute, OMAFRA)

Use the sun to your advantage.  If you walk slowly along a corn row with the sun in front of the plants so that it is shining light through the leaves, you can often see the shadow of the WBC eggs.  Sometimes I will admit that the shadow turns out to be bird poop but often it is actually a WBC egg mass.

Third, STINK BUG EGGS: Don’t confuse WBC eggs for stink bug eggs.

Newly hatched WBC eggs (T. Baute, OMAFRA)
Stink Bug Egg Mass Ready to Hatch (T. Baute, OMAFRA)

Once you have found a WBC egg, it is pretty obvious that they are different than stink bug eggs.  But until you do, you question what you are looking at.  Stink bug eggs are laid in a very tight geometric shape… almost honeycomb like in pattern.  They start out more yellow, are slightly bigger and somewhat barrel shaped.  With a handlens you can really see the difference.


WBC Moth Hiding in Leaf Collar (T. Baute, OMAFRA)
Closeup of WBC Moth (T. Baute, OMAFRA)

Often we were finding egg masses on the second or third leaf from the whorl.  Usually the leaf that was the most fully expanded but also still erect at the top of the plant.  And the egg mass tended to be closer towards the leaf axil.  After finding an adult moth hiding in one of the leaf collars, I can see why we are finding the eggs too close to that collar.

Hope this helps you to find your own egg masses.  Don’t solely focus on one area of the field but get a good sense of what the population is like across the field.  And try not to get a kink in your neck.

3 thoughts on “WBC Eggs Found in Fields in Ontario

  1. Several egg masses found in Alvinston today. Looked like one had hatched or predators had cleaned it out. Are there any predators? Didn’t see larvae.

    1. Hi Don

      Yes there are a few predators that we have already found feeding on WBC eggs. Ladybugs and lacewing larvae seem to be the most common. Though given how many eggs are in one WBC egg mass, they have a lot of feeding to do to help reduce infestations. Perhaps overtime the predators will realize there is something to feed on in corn and build up their numbers, like they have done for us in soybeans.

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