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Earworm spikes continue, stink bugs also damage sweet corn

Posted: August 30, 2011

Earworms, armyworms, and stink bugs are showing up in PA sweet corn crops.

Brown marmorated stink bug damages sweet corn, and damage has been reported in York Co. and the DelMarVa area.  Bugs pierce the husk, leaving no sign on the outside of the ear, but kernels are fed upon, resulting in visible blemishes and dark areas. This bug is also common now in field corn, and soybeans.  In sweet corn, growers report that sprays with pyrethroids, or tank-mixes of pyrethroids with methomyl (Lannate), have been effective.

Corn earworm captures continue to be high.  Eight counties had sites exceeding 10/night this week or last, suggesting 3-4 day spray intervals: Blair, Bucks, Lancaster, Lebanon, Lehigh, Mifflin, Washington and Westmoreland.  Three counties – Lancaster, Lehigh, and Mifflin – had sites exceeding 50/night either this week or last week, suggesting 2-3 day intervals.  Growers are at risk of earworm damage, and should tighten spray intervals on silking corn, consider including the newer materials (Coragen, Belt, Volium Express, Radiant), and when using pyrethoids use them at the highest labeled rate.  Timing the first spray at very early silk is important.  When earworm pressure is this high, a single spray at silk to Bt-sweet corn is also recommended.  

Second generation European corn borer flight seems to be complete except in Lancaster County.  All spray options that are effective on corn earworm will also control corn borer.   If you have Bt-sweet corn, you can ignore concerns from corn borer, but should consider a single spray at silk for other pest species.

Fall armyworms are coming in from the west.  Erie has high captures, and there is a presence in Blair, Centre, and Schuylkill Counties. 

In summary, strong corn earworm spikes continue throughout PA, requiring tighter spray intervals to protect crops.  Recent counts suggest a 3-4 day spray interval in 8 counties.