Western Bean Cutworm Fact or Fiction – Fact #1

There are a few “facts” about our western bean cutworm research being delivered to growers at various meetings this month that are not correct.   I am sure the reps are not intending to mislead growers but I thought it was a good time to get the correct message out there, straight from the horse’s mouth, so to speak.

Over the next few blog entries, I will summarize each fact so that you are better educated and ready for the upcoming season.

FACT OR FICTION #1.   Western Bean Cutworm Overwintering Success in Ontario

FICTION – The overwintering research in Ontario indicates 100% survival of all larvae at all soil depths.

FACT:  Overwintering success is no where near 100% and has decreased since the beginning of winter.

Jocelyn Smith (UGRC) set up two overwintering trials at Ridgetown and Centralia.    16 inch deep tubes containing three different soil types were positioned in the ground.   WBC larvae were placed on the soil surface of each tube in the fall and allowed to burrow down into the soil.  A set of tubes were pulled up in December (Ridgetown) and January (Centralia).  Another set was pulled up in February at both locations.  The final set has been left in the ground to see what moth emergence is like in June from these tubes.  Inch by inch, layers of soil were removed from the tubes to locate the larvae and determine what condition they were in.

Results so far indicate that although survival rate was looking promising in the sandy loam soil in particular in early winter, it greatly diminished over time.  By February, overwintering success was only at 0% to 37.5%, depending on soil type.  Though it does look like they can get deeper down in a sandy loam compared to the other soil types tested.  Michigan is seeing similar results from the trial they established there.

SO WHAT?  Admittedly, this is only one year’s worth of data.  And these are essentially small plot trials.   But this does give us an idea of what winter was like for them here in Ontario in some soil types.  We shouldn’t expect every larvae that went into the fall/winter to survive and emerge this spring.  But 2011 could still be a decent WBC year.  I am still concerned about the Bothwell/Cairo area in particular, where there were A LOT of larvae present in the fall that attempted to overwinter in the soil.  We will be keeping a close eye on moth emergence in that area this spring to see what the actual risk is.  But at least we are learning a little bit more about this pest and what it can and can’t do well in Ontario.

Next FACT OR FICTION:  Claims that some trap sites were catching 1000 moths per day (1000s) in 2010….I’ve got the real numbers…. Stay tuned.