Sweet Corn

Low numbers of European corn borer (ECB) moths continue to be captured, with little change from the previous week.  We anticipate that this initial flight is nearing its’ end.  The highest adult activity is currently Gloucester County (see map below at right).  Whorl corn is the primary target for egg laying, and injury as high as 40% of plants infested has been found in Hunterdon County this week.  This high feeding percentage is an outlier relative to what scouts are typically finding this season.  Most infestations are in the single-to- mid teens in terms of plants infested.  It is typical for feeding percentages to rise as the moth catch declines.  We expect feeding to increase for the next 1-2 weeks before peaking.

Look for the characteristic “shot-hole” type of feeding (photo  below at right) and consider treating when infested plants exceed 12% in a 50 plant sample.  As plantings proceed to the pre-tassel stage, ECB larvae may be found in emerging tassels (see photo at left).  It is a good idea to treat individual plantings as they move into the full tassel/first silk stage one time.  This eliminates any ECB larvae that have emerged with the tassels as they begin to move down the stalk to re-enter near developing ears.

Useful insecticides for this particular application include synthetic pyrethroids (IRAC Grp 3), spinosyns (including OMRI approved Entrust) IRAC Grp 5), and diamides such as Coragen or Vantacor (IRAC Grp 28) or materials such as Besiege which include the active ingredient in Coragen.  Synthetic pyrethroids alone should NOT be used for corn earworm (CEW) protection on silking corn.  Control with these materials is very inconsistent.

The highest nightly trap catches of ECB for the week ending 6/16/21 are as follows:

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