Posted: August 8, 2012
Shelby Fleischer, Penn State Entomology and Extension, (firstname.lastname@example.org)
Corn earworm (CEW): Sites in Blair, Franklin, Lancaster and Montgomery Counties suggest the widest of spray intervals, and slightly higher counts in Chester, Mifflin and Washington Counties suggest tightening to a four to five day spray interval. Otherwise, most sites continue to be below a spray threshold. Hot spots are appearing in southeastern Virginia and in Delaware, but average counts in Pennsylvania are trending low so far.
European corn borer (ECB): Overall counts are low. Multiple sites are showing a second generation flight, but only Centre County has dramatically high counts. The pattern of low counts suggests that poor survivorship occurred in earlier generations, perhaps from significant acreage of Bt-field corn acting as a sink, or that controls are working on the farms where the traps are set. Corn earworm sprays will cover whatever corn borers are out there.
Fall armyworms are being detected, but not anywhere near damaging levels.
Other species to watch for: As you cut back sprays, remember to scout for silk feeding from beetles (Western corn rootworm adults, Japanese beetle, and others), and for sap beetles moving into ears. These problems tend to be spotty, and can be controlled with a single spray at silk. Also, a summer generation of brown marmorated stink bug is emerging as adults now, and can move into sweet corn. Check edges of sweet corn fields for stink bugs. And a second or third generation of true armyworm is appearing as a pest in field crops, and could show up in sweet corn. In most years, true armyworm only presents a risk during its first generation, but this year we had an extraordinarily high density of first generation true armyworm…so the second or third generation could present a risk. Scout unsprayed fields for silk-feeding, sap beetles, stink bugs and true armyworm.
In summary, CEW trap captures are exceeding thresholds, but mostly at the widest of spray intervals. ECB are in their second generation flight, but counts are low except in Centre County. Sprays for earworm should be effective against corn borer. Scout unsprayed fields for silk-feeding, sap beetles, stink bugs and true armyworm.
For more information including maps and recent trap counts visit < www.pestwatch.psu.edu >.