Two More Pests To Consider
Posted: June 29, 2016
Two migratory pests that are relevant for field and forage production have arrived in Pennsylvania and growers should keep in mind some of the details of their biology and control.
True Armyworm reports have been low so far this year, but growers should keep in mind that this is the time of year that true armyworm are found in corn and hay fields. Very few transgenic, insect-resistant corn hybrids protect against true armyworm so I encourage growers to scout their corn and hay fields looking for armyworm populations and any associated damage. Some growers will elect to add insecticides to post-emergence herbicide applications to help control armyworm, but these treatments typically do not protected fields against infestation because they are not timed to coincide with armyworm populations.
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/grasses along field margins or on small grains and move to corn when weeds killed or small grains are harvested. Armyworm can occasionally cause problems feeding on small grains (often clipping heads of small grains), 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 factsheet provides more information on armyworm.
Potato leafhopper also migrates in from southern states, and has arrived in Pennsylvania. In Centre County, we have scouted alfalfa fields that are below economic threshold, but growers should be aware that potato leafhopper is now here and growers should scout their populations to determine if they exceed economic threshold. Recall that potato leafhopper populations can be very spotty, so dusty off your sweep nets and scout those fields to check your local populations. Our potato leafhopper factsheet provides more details on this pest, scouting protocols, and economic thresholds.