Forest Snapshot September 2026

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

Heading into autumn, Pennsylvania's deciduous trees and shrubs will turn the forest shades of reds, oranges, and yellows. One native understory tree of note is sassafras (Sassafras albidum), whose leaves will shift to vibrant a mixture of yellow, burgundy, crimson, and orange. The leaves come in 3 shapes, a trait described botanically as polymorphic. On the same tree, leaves will be oval-shaped, one-lobed or mitten-shaped, and two-lobed or resemble a "chicken foot". Sassafras is an aromatic tree that produces the essential oil, safrole, in all parts of the plant. Try crushing a leaf or scratching a stem to smell the fruity and spicy fragrance this season while admiring the starburst effects of its fall foliage.

Wildlife and Insects 

In the fall, hawk migration begins, with large numbers of sharp-shinned hawks and red-tailed hawks moving further south. In October, porcupines will be searching for mates throughout the month. Courtship involves nose-rubbing, teeth-chattering, and the male walking upright on its hind feet.

During these fall months, the forest's floral community is rapidly changing from the flowering shrubs (blackberries, raspberries, wineberries) to the fall aster community (goldenrods, wood asters). With these changes we also see a shift in bee communities. Many of the solitary bee species (which comprise ~90% of Pennsylvania's bee species) have completed their "life cycle" for the year. The young are developing in their nests, be they underground or in woody cavities, and will overwinter either as pupae or as full adults. These individuals will wait for the conditions to be appropriate for their reemergence. Usually, the environmental cues on which they await are the photoperiod (how long the days are) and the temperature. While the solitary bees are tucked away, our native bumble bees are often still active, taking full advantage of the aster blooms. Around this time, the queen will stop producing workers and will have fully switched to producing males and the gynes, who are to be next year's queens. The males will seek out the gynes of other colonies and mate, after which they will die. The gynes will consume as many resources as they can before seeking out a nest in which to overwinter. Bumble bee gynes go into what is known as diapause, a type of hibernation in which they reduce their metabolic rate and consume less reserves. They will ride on these resources until next year, when the cycle will begin anew. Along with bumble bees, you may see many wasp queens, non-migratory butterflies, and fall beetles frequenting the asters. These flowers are crucial resources for the insect community in late summer and are a great addition to a forest meadow or your own backyard!