A quick note about Cutworm feeding

I have had a few reports of spraying for cutworms and feeding damage.  This is one of those instances when it is good to be absolutely sure of your diagnosis because you could be spending money needlessly.  All cutworms are NOT the same.  As we discussed last week, Black Cutworm moth catches had reached levels that trigger us to begin counting heat units (300) as a benchmark to scout for damage.  Black Cutworm moths come in from the south on weather fronts; lay their eggs on green material, the eggs hatch and then the larvae begin to feed.  This is the process that requires around 300 heat units to occur. 

Reports began to filter in last week about cutworm feeding and subsequent spraying.  Unless you are in the very southern end of our 3-state area, it is unlikely (I did not say impossible) that Black Cutworms are cutting corn.  It could very well be that what you are seeing is damage from Dingy cutworms.  Dingy cutworms over-winter in the three state area as young larvae and begin leaf feeding earlier in the year.  The important thing here is that it is primarily leaf feeding with Dingy cutworms.  They typically do not cut plants below the surface.  This is a very important distinction because the two species are not easily distinguished apart from each other. 

It is possible that you could be finding Dingy cutworms (primarily leaf feeders) and be encouraged to spray right away.  I'm not saying that this is necessarily an incorrect recommendation because every situation is different, but I am saying that Dingy Cutworm leaf feeding is typically not terribly damaging to corn stands and a knee jerk reaction to spray may not be an economically sound decision.  Here is a link to an Iowa State newsletter from 2001 that does a great job explaining the issue and has great pictures as well.

http://www.ipm.iastate.edu/ipm/icm/2001/5-7-2001/earlyscout.html

The link below has pictures of black and dingy cutworms as well as other caterpillars you might find in your corn field this time of year.

http://www.ipm.iastate.edu/ipm/icm/2000/5-8-2000/cutworm2000.html

Hope this helps and please don't hesitate to call with questions.  The best thing to do is scout your fields and get help when needed.  Have a safe spring!