Why is my oak tree dying? Featured Video

Older oak trees have been plagued with health problems and are dying in large numbers throughout Maryland. Why? Both researchers and homeowners are asking the same question. The tree diagnostic laboratories have identified an assortment of diseases and pests on the dying trees. Yet no single, conclusive problem is killing them all. It remains a mystery. A few facts that everyone agrees on are these: We have never had so many mature oaks in our forests, so maybe this is the way they naturally decline. We experienced unusually wet summer weather in 2018 and 2019. Researchers believe this could have compromised the relationship between the mature oak roots and the fungus on which they depend for water absorption. As a homeowner, you can try to alleviate oak drought stress. If we experience a July/August drought, watering the area around the drip line of a tree can reduce stress. The objective would not be to stimulate growth with volumes of water, but instead to sustain the tree during the drought period. If your oak is in a lawn and you feed the turf once a year, that will suffice. Visit the Home and Garden Information Center website for a summary article.

Joyce Browning Horticulturist, Master Gardener Coordinator Video credit: Bethany Evans Longwood Gardens Professional Gardener Program Alumni; CPH

Why are Oaks Declining? Dr. Dave Describes 3 Oak Diseases

oak wilt symptoms
Leaves showing oak wilt symptoms, Pittsburgh, PA (Photo: Dave Clement)

We’ve recently received inquiries about oak trees declining and dying. People usually want to know if this is caused by oak wilt. Importantly, oak wilt is not known to occur widely in Maryland. Two common leaf diseases of oaks in Maryland are oak anthracnose and bacterial leaf scorch of oak.

oak anthracnose
Oak anthracnose

Oak anthracnose is caused by a fungal pathogen, Apiognomonia quercina, and it typically is a cool, wet weather, springtime disease. In wet cool summers like the one we’re experiencing this year however, the symptoms can continue through the season. Most oak species will show a range of symptoms scattered through the leaf canopy. Symptoms range from small brown spots and irregular dead areas on distorted leaves to severe blight that kills twigs and causes leaf shriveling. This disease in oaks typically doesn’t cause much leaf drop.
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