Beech leaf disease
Litylenchus crenatae mccannii
Dark bands between the veins of a beech leaf, seen best from below against the light. First found in 2012 and spreading fast, with no treatment yet.
What you'll see
- Dark green or almost black bands between the lateral veins, striping the leaf — hold a branch overhead and look up through it.
- Banded areas thickened and leathery to the touch, with a crinkled texture.
- Leaves curled, cupped and smaller than normal as the infestation builds.
- Buds aborting, so whole branches leaf out sparsely or not at all.
- Canopy thinning from the bottom up, and young trees dead within two to seven years.
Why it happens
A microscopic nematode that lives and breeds inside the leaf buds, feeding on the tissue as it forms — which is why the damage is already set into the leaf when it unfolds. It was first identified in Ohio in 2012 and has spread rapidly through the northeast and into Canada. Exactly how it moves between trees is still being worked out; birds, insects, rain and human movement are all suspected.
American beech throughout the northeast and Great Lakes states, and European and Oriental beech in gardens. Young and understory trees die fastest; mature trees decline over a longer period. It is spreading faster than the research on it.
Treating it
- There is no established treatment for a garden tree yet. Some trials of phosphite and of potassium salts show promise but nothing is settled.
- Water deeply in drought and mulch the root zone; a tree fighting this cannot afford any other stress.
- Do not fertilize heavily, which forces growth the tree cannot support.
- Remove dead branches for safety and have a declining tree assessed.
- Report it if the disease is new to your county — the distribution map is genuinely being built from these reports.
Keeping it away
- Clean tools, boots and equipment when moving between beech trees, especially in wet weather.
- Do not move beech nursery stock or leaf litter between areas.
- Keep beech trees well watered and unstressed.
- Plant something else where beech is being lost; there is no resistant beech available yet.
- Watch trees each June, which is when the banding is most visible.
See also
The Cottage Garden Companion — the gardener's apothecary at cottagegardencompanion.com