Common Tree Diseases & Pests in Wausau, Wisconsin

Oak Wilt

• Symptoms: Rapid leaf wilting, browning, and premature leaf drop, especially in red oak species.
• Cause: Fungus spread by sap beetles or through root grafts.
• Management: Immediate removal of infected trees, trenching to prevent root transmission, and fungicide injections for healthy trees nearby.

Dutch Elm Disease

• Symptoms: Yellowing leaves, branch dieback, and eventual tree death.
• Cause: Fungus carried by elm bark beetles.
• Management: Remove infected branches promptly, apply fungicide injections, and maintain beetle control through insecticide treatments.



Apple Scab

• Symptoms: Dark spots on leaves and fruits, leaf curling, and early leaf drop.
• Cause: Fungal spores thriving in damp conditions.
• Management: Regular pruning, proper air circulation, application of fungicides in spring, and planting resistant varieties.

Anthracnose

• Symptoms: Irregular brown leaf spots, leaf curling, and twig dieback.
• Cause: Fungus developing in wet conditions.
• Management: Enhance airflow by pruning, avoid overhead watering, and use fungicidal sprays if needed.

Emerald Ash Borer (EAB)

• Identification: Metallic green beetle whose larvae feed under bark.
• Symptoms: Crown dieback, woodpecker damage, D-shaped exit holes.
• Management: Chemical treatments, removal of severely infested trees, and proactive planting of diverse tree species.

Gypsy Moth

• Identification: Caterpillars with distinctive blue and red dots.
• Symptoms: Extensive defoliation weakening trees over time.
• Management: Application of biological insecticides, pheromone traps, and fostering natural predators.

Asian Longhorned Beetle

• Identification: Large black beetle with distinctive white spots and long antennae.
• Symptoms: Round exit holes, sawdust-like frass, branch dieback.
• Management: Immediate reporting to local authorities and removal of infested trees, as there’s currently no chemical control.

Pine Bark Beetles

• Identification: Small beetles that bore into bark, causing extensive damage beneath.
• Symptoms: Fading needles, pitch tubes on bark surface, tree decline.
• Management: Maintaining tree vigor, removing infected trees, and preventive insecticide treatments.