Beech leaf disease

Overview

• Invasive – nematodes of this genus are found in the Pacific Rim (Korea, Japan and New Zealand).
• The disease causes leaf deformity in beech trees of all ages.
• Young trees die as a direct result of this disease.
• First detected in Ontario in 2017, the disease is present along the shore of Lake Erie and in Toronto.

“Invasive” refers to a species that has moved outside of its native habitat and threatens the new environment, economy or society by disrupting local ecosystems.

Host species

Beech leaf disease is found in:

• forests with American beech (Fagus grandifolia)
• plantings of European (sylvatica), Oriental (Fagus orientalis) and Chinese (Fagus engleriana) beech in North America

Characteristics and life cycle

• Nematodes are present in leaves before symptoms occur.
• Nematodes feed on leaf tissue between veins, causing leaf damage.
• Nematode numbers increase from spring to fall and they overwinter in buds and leaf litter.
• How the nematode is spread is unknown and research is underway; other nematodes are spread by mites, insects, animals and in infected plant material.

Symptoms and damage

• Early symptoms are dark-green stripes or bands between lateral veins of leaves.
• Severe symptoms include thickened or leathery leaves that may be yellow, curled or deformed; leaves may drop early and buds may not develop.
• Sapling-sized trees may die within two to five years, with older trees taking longer to show effects.
• Infected trees can be more susceptible to other pathogens.

Control measures

The nematode thought to cause beech leaf disease can unintentionally be spread to non-infested forested areas.

To stop the spread, do not move:

• beech seedlings
• leaf litter
• firewood