Ask The Agronomist Blog

Jacob Evans Japanese Beetle and other silk clipping insects

June 21, 2010
Posted by: Jacob Evans, Regional Sales Agronomist

I noticed some early planted corn starting to shoot tassels in the southern part of my region on June 19th.  That got me curious with the year as we have seen it so far there have not been many insect concerns.  But when I walked out into the corn fields I started seeing an insect we need to watch.  Japanese Beetles had hatched and were abundant.  I only found beetles in the tasseled fields, there were not any adult beetles in untasseled fields yet, but while digging some roots this morning in a later planted field corn was at V8 and I was finding several japanese beetle larva in the cocoon stage or pupating. I do not know if they will reach economic theshold levels this year but want to refresh on my concerns here.  If silks are being cut back to less than 1/2 of an inch before 50% of pollination occurs, and beetles are present and feeding, then treatment is warranted.  This is the case for Corn Rootworm beetles also, these guys should start to hatch in the next few days also.  My big concern with these insects are not the pollination issues this year.  With the moisture we have right now I do not think pollination will be impeded much by silk clipping.  But, after pollination occurs the beetles continue to feed, elliminating the protective silk cap and alot of times even feeding on the developing kernels on the ear tips.   With as much problems with ear rots and kernel damage we had last year I wondering if we should start thinking more about this.  With the ear opened up and as much moisture is available could that be hurting grain quality and opening a roadway for ear rots?  Should the threshhold be dropped to insects feeding on 50% of the ears pollinated or not?  I am looking into this more and if anybody has any thoughts on this let me know.  Until later have a good week

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