Garden Q&A: Why are some trees in my beech hedge dying?

I've noticed a white substance on the leaves, which appears to be a form of mildew. How should I treat this disease?

Keep watering your hedge deeply throughout the dry spell and feed it around the base with plant food. File picture

Tue, 30 Jun, 2026 - 19:13

Peter Dowdall

Question

I planted a beech hedge in the spring of 2025. The trees were well maintained and doing very well, but recently a number of trees have begun to lose their leaves and die. I have noticed a white, powdery substance on the leaves, which appears to be some form of mildew. How can I treat this disease and get trees back on track?

Answer

The white coating on your beech hedge could be powdery mildew, but it may equally be woolly beech aphid, which produces fluffy white patches on the undersides of leaves and can be damaging on a newly planted hedge.

Check the undersides carefully; if the white material is there rather than on the leaf surface, the aphid is the more likely culprit.

Either way, start by pruning out the worst-affected shoots and removing them from the garden entirely. This helps reduce the problem, whichever it is.

For aphids, direct a strong jet of water at the undersides of the leaves regularly, and try a diluted garlic spray, which acts as a natural deterrent. Encouraging ladybirds and hoverflies into the garden will also help bring numbers down over time.

Keep watering the hedge deeply throughout the dry spell and feed around the base of the plant with a biochar-based plant food such as Nutrichar, which will encourage healthier growth and plants more resistant to attack.