Armyworm and potato leafhoppers have been found in corn and alfalfa fields around Pennsylvania. Scout your fields and refer to this article for a refresher on threshold levels and monitoring suggestions.
Reports of true armyworm have been very low this year, but last week I visited a 40-acre corn field in Clinton County that was well infested with armyworm. The grower did not use an insecticide in his burndown treatment (it probably would not have protected the field against this infestation that developed three to four weeks following burndown), but a scout who was checking the field regularly noticed the damage exceed economic threshold and had the field sprayed with lambda-cyhalothrin, which saved the field. I highlight this example for two reasons. First, armyworm is around and corn, hayfield, and small grain fields should be scouted to look for damage. Second, this grower relied on IPM and it worked just as it is supposed to with scouting and application of a rescue treatment.
As a reminder, a few more details on armyworms follow. Adult moths fly into Pennsylvania after overwintering in the soil in states to our south. Females lay their eggs on weeds and/or grasses along field margins or on small grains and move to corn when weeds or grain cover crops are killed with herbicides. Armyworm can occasionally cause problems feeding on small grains sowed for harvest, but tend to be problematic more often in corn when small grains are harvested because armyworms move to young corn plants. Armyworms tend to feed at night along the margins of corn leaves, avoiding midribs. During the day, larvae hide in leaf sheaths or in the soil or leaf litter. Rescue treatments are usually the most efficient and economical tactic for managing true armyworm because populations are very spotty and preventative applications may not have sufficient residual activity to kill caterpillars that hatch out later. Armyworms can warrant treatment should infestations reach 25% of plants in a field. A recently revised fact sheet provides more information on armyworm.
One other pest of note is potato leafhopper. In Centre County, we have scouted alfalfa fields that are above economic threshold and showing signs of hopperburn. Recall that potato leafhopper populations can be very spotty, so dusty off your sweep nets and scout those fields to check your local populations.
Source : psu.edu