Forest Snapshot September 2025

Breaking News

EHD Detected in White-tailed Deer in Pennsylvania 

Cases of epizootic hemorrhagic disease (EHD) have recently been detected in white-tailed deer in several Western PA counties, including Erie, Mercer, Butler, and Lawrence counties. Several other reports in southwestern and southeastern PA are being investigated. This viral disease is transmitted by tiny biting midges (gnats) that live near bodies of water. Symptoms can include swelling of the face and neck, drooling, open sores around or in the mouth, and unusual behavior like lethargy and lack of fear of humans. In the later stages of disease, many deer seem to be attracted to water; thus, it is common to find deer killed by EHD near water bodies.

EHD is usually fatal to deer in northern states, where outbreaks are much less frequent than in southern states. Depending on the severity, an outbreak can result in scattered deer deaths or alarmingly high rates of mortality within localized areas. Even after severe cases, deer populations rebound within a few years. To help track infections and outbreaks, people are highly encouraged to report sick-looking deer or deer that are dead with no obvious cause. The PA Game Commission 24/7 hotline is 1-833-PGC-WILD (1-833-742-9453). 

More information can be found on the PA Game Commission website:

• Public Plays Important Role in Monitoring EHD
• Deer Hemorrhagic Disease

Forest Health

Beech Leaf Disease Management 

The impacts of beech leaf disease (BLD; caused by the non-native foliar nematode Litylenchus crenatae ssp. mccannii) are wide-ranging across Pennsylvania, in areas of low to high beech bark disease (BBD) impact. Research and management trials are being conducted region-wide to determine the best strategies for reducing this impact and maintaining a component of beech in our forests.

In areas of heavy BBD impact, management of beech brush is important for forest regeneration. In the majority of these areas, BLD impacts to beech brush now mean that only cutting the brush is necessary prior to harvest; broadcast herbiciding is no longer a necessity. In some areas of more severe impacts, beech brush may no longer inhibit desirable regeneration even without cutting, due to much higher light infiltration.

Several pesticidal active ingredients and application methods are available in Pennsylvania, and are being tested.  Appropriate product, application method, timing, level of disease control, and duration of efficacy are all still in question for these products.

• Macro (high volume) trunk injection of Thiabendazole Hypophosphite as Arbotect 20S
• Micro (low volume) trunk injection of mono- and di-potassium salts of phosphorous acid as PHOSPHO-jet
• Soil injection or drench, or basal spray of Potassium phosphite. As PolyPhosphite30 (labeled as a fertilizer), soil injection or drench. As Reliant fungicide, basal spray. Soil injection requires specialized equipment. Basal spray and soil drench do not.
• Foliar spray of Fluopyram products, a fungicide and nematicide. There are several appropriately-labeled products for row crop, landscape, and residential, greenhouse and nursery use. We are working on finding an appropriately labeled product for forest use.

Silviculturally, stand density and beech brush management may help to maintain relatively healthy canopies of residual overstory beech. Research is ongoing in several New England states. By reducing host density and inter-tree competition, these silvicultural interventions are expected to improve residual tree vigor while simultaneously testing the epidemiological hypothesis that decreasing canopy leaf area can suppress the spread and severity of the moisture-dependent nematode. Understory beech will also be removed to determine whether limiting regeneration curtails upward nematode movement. Even-aged and uneven-aged management prescriptions are being tested.

Native Species

With the turn of the season, the nearly baseball-sized green fruits of black walnut (Juglans nigra) are appearing on the landscape across the state. Black walnuts are large deciduous trees, sometimes growing up to 150 feet tall, with wide canopies. Classified as shade-intolerant, black walnut saplings will rapidly grow to secure dominant canopy positions after a disturbance. Their roots exude an allelopathic chemical, called juglone, that inhibits the growth of some neighboring plants as a strategy to reduce competition for space. Not all plants are affected by juglone, but members of the nightshade family, including tomatoes and peppers, will not survive if grown under the shade of a black walnut.  

Black walnuts are culturally important trees that have a history of use. The rich, dark brown wood, harvested from trees that often grow tall and straight, makes for premium furniture, turned bowls, tools, and utensils. Nuts are a food source for many wildlife species and humans alike, with reliable production each year. Collect the nuts as soon as they drop, wear gloves to avoid staining, and set out those harvested in a place with good air circulation to allow the hulls to dry. Hulls and leaves will readily dye fabrics made from animal sources, like wool and silk, with little additional preparation. The result is a rich brown that deepens with time in the dye pot.

Keep an eye out for black walnuts this season. Their yellowing leaves will be among the first to fall. 

Wildlife and Insects

In October, you should start to notice changes in bird populations. Dark-eyed juncos and white-throated sparrows begin to return for the winter. Year-round residents, brown creepers may be more noticeable after leaf-drop, as they hop up and down tree trunks in search of insects. Hawk migration continues, with large numbers of sharp-shinned hawks and red-tailed hawks moving further south. Yellow-rumped warblers linger, but within a few weeks will move on to their winter habitat along the southern Atlantic coast. 

Reptiles will also become scarce. Eastern box turtles are heading underground to hibernate, digging a burrow about 5½ inches below the surface. Here, they can withstand freezing temperatures for many months.