Spongy moth (gypsy moth) larvae on oak tree bark.

Monitoring Timber Health for Pennsylvania Landowners

As a landowner in Pennsylvania, constantly monitoring the health of your forests is essential for ensuring their longevity. Protection against insects, pests and diseases in our Commonwealth’s forests is a very important part of the sustainable management of these forests. Forest protection is a key element of every forest management plan in Pennsylvania.
This is because these forests have experienced and continue to experience the effects diseases and insects can have on their composition, structure, and landscape. In 1904, Chestnut blight entered Pennsylvania and wiped out almost every mature American chestnut here, a dominant canopy tree with many benefits and of high value.
Today, there are several insects and diseases that continue to pose a serious threat to Pennsylvania’s timber including Emerald ash borer, Spongy moth, Hemlock woolly adelgid, Beech bark disease, Oak wilt and so on.
In this article, we are going to understand these damaging agents, learn to identify them and discuss ways to protect our forests against them.

Thinning Timber Stand

One of the key methods of protecting the timber from damaging agents is thinning your timber stands. Thinning is the practice of removing selected trees from a stand to promote the health and growth of the remaining trees. In an unmanaged stand, the trees grow too close together and they compete for sunlight and nutrients. As a result, they cannot grow properly and become more susceptible to disease and insects. Moreover, when trees are close, there are higher chances of spreading diseases and insects.
So, thinning is the number one technique at your disposal to reduce such risks. Thinning not only protect your stand, but it also often leads to better bole diameter and merchantable height. And thinning conducted at the latter stages of the rotation cycle can also generate revenue.
However, it is important to identify which trees to cut and which trees to leave behind. This is often found in the thinning plan, which should be prepared with the help of professionals. But there are often ways to identify which trees are problematic or have diseases on them.

Salvage Cuttings of Damaged Timber

Salvage cutting is a more specific means of forest protection against insects and pests. It involves removing the timber that has already been damaged or even killed. Removing timber that has been damaged by diseases reduces the chances of it spreading even more. Also, even if the damage is caused by fire, drought, or animals, removing such timber is the best management practice since they can be breeding grounds for insects, fungus and pests.

Spotting Disease in your Woodland

Early detection of the disease and subsequent treatment can help prevent its spread and minimize its impact on your forest. To be able to detect these diseases, you need to first, conduct regular monitoring of your forest stand and second, be able to identify their signs on the trees. Diseases that are prevalent in Pennsylvania forests are Beech Bark disease, Beech leaf disease and Oak wilt.

  1. Beech Bark Disease
    Beech Bark disease is a canker disease which is caused by the combination of a fungal pathogen (Nectria coccinea) and an insect (Cryptococcus fagisuga). This disease is mostly spread in the northern half of Pennsylvania but has been recently detected in the Mifflin and Chester counties.
    Signs of this disease include small canker formations on the trunk which are reddish-brown. Branches start to die off and the canopy reduces. As cankers develop, they can also combine to girdle the tree, which disrupts the flow of water and nutrients in the tree and causes death.
  2. Beech Leaf Disease
    Beech leaf disease has been detected in several counties within Pennsylvania since 2016 with the most recent detection in the region from Susquehanna valley to southeastern Pennsylvania. It is a particularly serious threat to beech, one of the most common hardwood species in the commonwealth, because it affects beeches at all stages from seedlings to mature trees and there is no known cure for this disease other than removing the infected trees.
    Symptoms of this disease start as dark green banks on the leaves, and leaf curling, followed by necrosis, wilting, defoliation and finally branch dieback and tree mortality within 2-3 years.
  3. Oak Wilt
    Oak wilt is a fungal disease that affects all species of oak in the commonwealth. As mixed oak forests are abundant in the commonwealth and oak is a popular urban tree, oak wilt possesses a threat to both urban and rural oaks. It was confirmed in Pennsylvania in the 1960s but is not widespread.
    Identification of oak wilt can be done from leaves which have wilted, turned brownish or dropped. Between May to August, the fungus is in the active stage and it is easy to notice the affected leaves against the other green ones. As the infection advances, entire branches are dead and in the latter stages, splitting of bark occurs.

Some other diseases common in Pennsylvania include:

– Gall Rusts
– Black Root Rot
– Fire Blight
– Anthracnose
– Crown Gall

Common Insect Damage Found in Pennsylvania’s Forests

There are both native and non-native insects that threaten Pennsylvania’s forests. Some of the ones commonly hampering timber health and quality include the followings:

  1. Spongy Moth (Lymantria dispar dispar)
    Since the 1970s, the Spongy moth, previously known as the gypsy moth, has been the primary agent of mortality of trees in the commonwealth. There have been several outbreaks including the current one which began in 2021 and is ongoing today. Killing millions of trees and causing massive loss of timber and capital, the DCNR’s Bureau of Forestry’s spongy moth program has actively tried to manage this pest through monitoring and treatment through mechanical, chemical and biological means.
    As defoliation occurs, the tree dies in around a year or even within a single season for conifers. So, the best chance of dealing with this pest is to actively conduct surveys for eggs.
    This detailed guide, made specifically for private landowners, helps to deal with the moth effectively in private lands.
  2. Emerald Ash Borer (Agrilus planipennis)
    The Emerald Ash Borer is a beetle native to Asia and after being detected in Pennsylvania in 2007, it has spread across almost all counties of the Commonwealth. It is distinctly metallic green in colour and measures only half an inch. The beetle larva is the culprit here, which feeds only on ash trees of all types. After about three to five years of infestation, the tree dies.
    Signs and symptoms of its infestation are dieback of the upper crown, epicormic branching (shoots arising from the lower trunk), splitting, and flaking of bark, holes in the bark, and galleries below the bark.
  3. Hemlock Wooly Adelgid (Adelges tsugae)
    The Eastern Hemlock was officially named the state tree of Pennsylvania in 1931. In the late 1960s, Hemlock wooly adelgid insect was detected in the state that started causing defoliation and mortality in the Eastern Hemlock trees.
    Needle drop, branch dieback and then eventually tree mortality are observed in infected stands. While the DCNR has been using integrated methods such as biological control, insecticides, silviculture and breeding to manage this problem, landowners mostly rely on insecticides as the practical option to deal with this insect. Since this can be expensive, landowners are forced to wait, watch, and hope for the trees to survive on their own.

Some other insects that are common in Pennsylvania include:

– Spotted Lantern Fly
– Asian Jumping Worms
– Forest Tent Caterpillar
– Eastern Tent Caterpillar
– Elongate Hemlock Scale

Pennsylvanian forests have been in a constant struggle for health and survival against both native and non-native species of pests, insects, fungi, and diseases. External factors like climate change, pollution, drought, wind, and fire further exacerbate this problem as they affect both the trees and the insects. To produce valuable timber and other services from the forest, as a private landowner, it is extremely important to deal with a range of different damaging agents. Constantly monitoring and surveying the forest for signs and symptoms discussed above, integrating forest protection in management plans and contacting professional forestry services as soon as signs of disease or insects appear is one of the best practices to maintain the quality timber production and the overall health of your forest.

Contributed by Sandesh KC

PreQualification for Sale of Timber Form

Contact One of Our Partners Specializing in smaller timber harvests

Upland Timber
Quarryville, PA


Sam the Tree Guy
Ronks, PA


Three Easy Steps to Get Your PayDay


Call or message us. We discuss your needs with you.


We meet with you to guide you through key decisions and create a harvest plan.


Strong cash value and your forest growing back in beauty = smiles all around.

Message or Call Us