Friday, July 23, 2010

"New" Pest Arrives

This is a picture of a western bean cutworm trap positioned by our Impact Plot.  OMAFRA crop reports have been highlighting the increases in trap counts for the last month.  A new bug gives agronomists something to talk about, which can lead us to think we about to be overwhelmed by this latest threat.
The western bean cutworm is a relative newcomer to the local crop scene.  It was first detected in Ontario in 2008 and has been steadily increasing since then.  This pest first appeared in Colorado, hence the name "western".  It also feeds on edible beans.  The western bean cutworm has been able to flourish because the european corn borer has been eliminated as a threat in most corn fields, thanks to Bt technology.  To make a complicated story short, the corn borer larvae would eat the western bean cutworm larvae for breakfast, so as long as european corn borer were present, the western bean cutworm would never survive.  Removing the corn borer gave the western bean cutworm an open door.   


This is a picture of western bean cutworm eggs taken from a field near Strathroy by Willy Ann Kennes, a Pioneer Sales Rep.


This is the same egg mass 24 hours later and you can see the young larvae beginning to hatch.  The larvae grow quite rapidly and will soon look like the critter below.

And they can do a significant amount of damage.

Do I expect this beast to become a huge problem this year?  No.  For one thing, the numbers are not high enough yet to cause real yield loss.  For another, the Herculex Bt gene that Pioneer uses in most of their lineup for corn borer protection also gives good control of the western bean cutworm.  Herculex is the only Bt gene that provides growers some insurance against this newest invader. 
But, we need to remain vigilant going forward because experience proves the western bean cutworm population will continue to grow, along with agronomist job security.

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