Here are the Top 10 Bugs & Diseases Killing Trees and Plants in Pennsylvania

As an expert arborist, I want to highlight the top tree-killing pests and diseases threatening Pennsylvania’s trees and plants during the summer months. These threats not only compromise the health of individual trees but also pose significant risks to the state’s diverse forest ecosystems.extension.psu.edu

1. Spotted Lanternfly (Lycorma delicatula)

Since its discovery in Pennsylvania in 2014, the spotted lanternfly has become a pervasive invasive species. Feeding on the sap of over 70 plant species, including maples, black walnuts, and grapevines, these insects excrete a sticky substance called honeydew. This promotes the growth of sooty mold, which hinders photosynthesis and weakens plants. Their rapid spread is facilitated by human activities, such as transporting infested materials. en.wikipedia.org+8realsimple.com+8verywellhealth.com+8en.wikipedia.org+2time.com+2verywellhealth.com+2

2. Emerald Ash Borer (Agrilus planipennis)

The emerald ash borer is a metallic green beetle that has decimated ash tree populations across Pennsylvania. Larvae burrow beneath the bark, disrupting the tree’s ability to transport water and nutrients, leading to tree death within a few years of infestation. All native ash species are susceptible, and the beetle’s spread has been exacerbated by the movement of infested firewood. en.wikipedia.org

3. Bacterial Leaf Scorch (Xylella fastidiosa)

This bacterial disease affects several hardwood species, including red oaks, elms, and sycamores. Transmitted by leafhoppers and spittlebugs, it causes leaf browning, premature leaf drop, and eventual tree decline. There is currently no cure, making prevention and early detection crucial. rickscertifiedarborists.commcfarlandtree.com

4. Oak Wilt (Bretziella fagacearum)

Oak wilt is a fungal disease that spreads through root grafts and insect vectors, notably affecting red oaks. Infected trees exhibit wilting leaves, discoloration, and rapid death. The disease can spread quickly within oak populations, necessitating prompt removal of infected trees and root disruption to prevent further transmission.

5. Hemlock Woolly Adelgid (Adelges tsugae)

This tiny, aphid-like insect targets eastern hemlocks, Pennsylvania’s state tree. By feeding on the tree’s sap, it causes needle loss, branch dieback, and eventual tree death. The presence of white, woolly egg sacs on the underside of branches is a telltale sign of infestation. pa.govmcfarlandtree.com

6. Beech Bark Disease

A combination of the beech scale insect and fungal pathogens leads to beech bark disease. The scale insect creates wounds that allow fungi to enter, resulting in cankers, bark splitting, and tree mortality. Affected trees often exhibit a woolly appearance due to the scale insects. pa.gov+4en.wikipedia.org+4wvia.org+4

7. Anthracnose

Anthracnose is a group of fungal diseases affecting various deciduous trees, including oaks, maples, and sycamores. Symptoms include dark, sunken lesions on leaves, premature leaf drop, and twig dieback. While rarely fatal, repeated infections can weaken trees over time. rickscertifiedarborists.comclausertreecare.com

8. Apple Scab (Venturia inaequalis)

Primarily affecting crabapple and apple trees, apple scab causes olive-green to brown lesions on leaves and fruit. Severe infections lead to premature leaf drop and reduced fruit quality. The fungus thrives in cool, wet conditions, making early summer a critical period for management. clausertreecare.com+2rickscertifiedarborists.com+2mcfarlandtree.com+2

9. Beech Leaf Disease

First identified in Pennsylvania in recent years, beech leaf disease is associated with a nematode infestation. It causes dark banding between leaf veins, leaf curling, and reduced canopy density. The disease progresses rapidly and can lead to tree death within a few years. pa.gov+5wvia.org+5en.wikipedia.org+5

10. Birch Leafminer

Birch leafminers are sawfly larvae that feed between the upper and lower surfaces of birch leaves, creating blotchy mines. Heavy infestations can cause significant leaf browning and premature drop, stressing the tree and making it more susceptible to other pests and diseases. en.wikipedia.org

Protective Measures:

Regular Monitoring: Inspect trees frequently for signs of pests or disease.
Proper Sanitation: Remove and destroy infected plant material to prevent the spread of pathogens.
Avoid Transporting Firewood: Many pests spread through the movement of infested wood.
Consult Professionals: Engage certified arborists for diagnosis and treatment recommendations.

Staying informed and proactive is essential to preserving Pennsylvania’s rich arboreal heritage.