🌿 Common Tree Pests and Diseases to Watch for This Spring in London

As spring begins to roll in across London, trees are bursting back to life — but so are many of the pests and diseases that can threaten their health. While the city’s diverse mix of gardens, parks and street trees is something to celebrate, it also creates ideal conditions for certain insects, fungi and infections to spread quickly.

Here’s a helpful guide to the most common tree pests and diseases affecting trees in London during the spring, how to spot them early, and when to call in a professional.

🐛 1. Box Tree Caterpillar

Tree/shrub affected: Box (Buxus) Peak season: March–October Common in: South London, private gardens, parks

What to look for:

Webbing on box hedges
Skeletonised leaves
Black-and-green striped caterpillars

Why it matters: This invasive species has spread rapidly across London and can decimate box hedges within weeks.

What to do: Early intervention is key — light pruning and pheromone traps can help, but larger infestations often need professional treatment.

🐞 2. Horse Chestnut Leaf Miner

Tree affected: Horse Chestnut Seen in: Many London boroughs — especially older trees in parks and along roads

What to look for:

Brown patches appearing between leaf veins
Early leaf drop (often starting in late spring)

Why it matters: While rarely fatal, repeated infestations weaken trees and make them more vulnerable to other issues.

What to do: Clearing fallen leaves and monitoring is important. A tree surgeon can advise on the tree’s condition and whether pruning is needed.

🍄 3. Honey Fungus (Armillaria)

Affects: A wide range of garden trees and shrubs Common in: Mature gardens, older properties, overgrown plots

What to look for:

White fungal growth under bark at base
Cracking bark or dead wood
Clumps of honey-coloured mushrooms in autumn (earlier signs often appear in spring)

Why it matters: Honey fungus is one of the most destructive root diseases in UK gardens and often requires professional diagnosis and action.

🐜 4. Aphids and Tree Scale Insects

Affects: Lime, maple, birch, cherry, and many ornamental trees Widespread in: Central and Greater London

What to look for:

Sticky residue (honeydew) on leaves or patio below
Leaf curl or discoloration
Black sooty mould developing

Why it matters: While often seen as cosmetic, large infestations can reduce tree health and encourage mold growth on nearby surfaces.

What to do: Encourage natural predators like ladybirds, but professional treatment may be needed for recurring infestations.

🌿 5. Powdery Mildew

Affects: Maple, oak, sycamore, ash, and fruit trees More common in: Shaded, damp gardens with poor airflow

What to look for:

White, powdery coating on leaves
Distorted or stunted new growth

Why it matters: Though rarely fatal, repeated infections weaken the tree and reduce its aesthetic and environmental value.

What to do: Improve airflow and prune where necessary. A tree surgeon can help assess whether the tree needs further care or treatment.

👨‍🌾 When to Call a Professional

Early spring is the best time to spot problems before they become serious. If you're unsure whether your tree is struggling with pests, disease, or just waking up after winter — we can help.

Our London-based team can: