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UNIVERSITY PARK -- With warmer weather, it's not just humans that get more active. There are many pests that could be affecting forests in the next few months. Some are established statewide and have cyclical population spikes and lows; others are newer and spreading across the state. Here's an overview of pests that are expected to make a large impact and/or spread further within Pennsylvania this year, and what can be done or is happening to address them.
As in years' past, this May, state agencies are coordinating the spraying of hundreds of thousands of acres of public forests with biological (e.g., BtK) and chemical (e.g., Mimic®) agents from aircraft in an effort to reduce defoliation due to the spongy moth. With the early warm-up, caterpillars may begin to hatch before May 1. Exact spray timing is
determined by larva development and oak leaf size. Spray blocks are mostly through the north central and south central parts of the state, with some blocks in Pike and adjacent counties. The treatment areas were identified during egg mass surveys conducted in 2023. Guides to surveying for egg masses, conducting aerial spraying on public land, and interactive maps of PA DCNR and PGC spray programs are available on DCNR's website. Spongy moth in the forest is most detrimental to oak stands. They can also defoliate fruit and nut trees and shrubs. The USDA Forest Service has a great guide which lists 36 tree species or species groups and whether they are susceptible, resistant, or immune to spongy moth defoliation. It also lists treatment options for small and larger
properties.