Posted: July 5, 2012
Shelby Fleischer (firstname.lastname@example.org), Penn State Entomology and Extension
Corn earworm (CEW): Most sites are capturing CEW, and sites in Bucks, Chester, Lancaster, Lehigh and Mifflin Counties have reached a spray threshold. Although catches are still low overall, they have been trending upward for about two weeks. Silking corn acts as a strong magnet to moths in your area. Warm nights are good flying nights for moths. Watch your traps carefully, or consider applying a single spray at early silk for high-value early-planted corn.
European corn borer (ECB): Populations, if established on your farm, are in larval or pupal stages. Lehigh, Northampton and Clinton Counties had high captures of first generation adults. Check for feeding damage in tassels. A single spray at row tassel will help clean up populations that established earlier.
Phenology models suggest adults will appear in southeast and southwest Pennsylvania within a week. Trap counts suggest the beginning of a second adult flight in Luzerne County. It is feasible that we had poor survivorship of first generation due to the very early emergence of ECB, prior to planting of corn, but if overwintering moths did establish and survive, we could be seeing the beginning of second adult flight soon after July 4th.
Fall armyworms (FAW) are being detected, but not at anywhere near damaging levels.
Western corn rootworm (WCR): Adults are emerging early this year. These beetles look similar to striped cucumber beetles, but with a yellow belly, as opposed to the black belly of striped cucumber beetles. Scout your corn to check for silk clipping by adult western corn rootworm.
Corn thresholds for worms in the ears: Vegetative corn should be scouted. Larger, longer-season varieties can tolerate 15 to 30 percent infestation rates without affecting yield; smaller early-season cultivars are more sensitive. If infestation rates are low, try waiting until "row-tassel" (when you can look down a row and just begin to see the tassels emerge). A single spray timed at row tassel will clean up low infestations prior to the corn moving into the reproductive stages. For multiple plantings, controlling the early season populations reduces problems later in the season.
Reproductive corn (tassel or silk) and the last vegetative stage (V12 stage, just prior to reproductive stages) attract moths. Spray timing can be adjusted according to moth flight, monitored with pheromone traps. Plotting the number of moths caught over time helps determine when populations are increasing or decreasing -- which is when to shorten or lengthen your spray schedule. Remember: Control programs need to begin at row tassel. Waiting until silking is too late for ECB and FAW.
For more information including maps and recent trap counts visit < www.pestwatch.psu.edu >.