Common Tree Pests and Diseases in Melbourne During Summer (2025)

Melbourne’s warm, humid summers create the perfect environment for tree growth – but also for pests and diseases. While healthy trees can resist most minor infestations, prolonged heat and dry stress can make even established trees vulnerable. Understanding the most common tree pests and diseases in Melbourne helps you identify problems early and protect your garden before damage spreads.

At Dawson Tree Services, our experienced arborists regularly treat and manage summer-related tree health issues. Here’s what to look for this season and when to call in professional help.

Why summer increases pest and disease activity

Heat, drought, and inconsistent watering create stress for trees, lowering their natural defences. Pests multiply faster in warm weather, and fungal spores thrive in humidity after summer rain. As a result, tree health problems can appear suddenly and worsen quickly if ignored.

Regular inspections and seasonal tree pruning help maintain airflow and reduce pest pressure – two key defences against most common issues in Melbourne gardens.

Common tree pests in Melbourne during summer

Some insects are harmless, but others can cause severe stress and long-term decline if not treated. The most common pests affecting Melbourne trees include:

• Lerp psyllids: Small sap-sucking insects that target eucalypts, leaving sticky residue and white sugary covers on leaves.
• Elm leaf beetle: A destructive pest that skeletonises elm leaves, causing browning and defoliation during hot months.
• Borer beetles: These insects tunnel into trunks and branches, leaving small round holes and sawdust-like frass.
• Scale insects: Appear as small bumps on stems and leaves, producing honeydew that encourages sooty mould growth.
• Aphids: Rapidly multiplying insects found on new shoots and leaf undersides, often leaving a sticky residue and curled foliage.

Most infestations can be managed with pruning, removal of affected limbs, and targeted horticultural treatments. Severe cases may require tree removal if structural damage or infection is advanced.

Common summer tree diseases in Melbourne

Fungal diseases spread quickly in Melbourne’s summer humidity, especially in dense canopies or poorly drained soils. Key diseases to watch for include:

• Powdery mildew: White, powder-like spots on leaves that thrive in warm, dry conditions with poor airflow.
• Root rot (Phytophthora): Caused by overwatering or poor drainage; roots decay and trees wilt even when soil is moist.
• Leaf spot fungus: Dark or yellowish circular patches on leaves, common in ornamental and fruit trees.
• Armillaria (honey fungus): A serious root disease that causes decay, dieback, and often death of mature trees.
• Sooty mould: A black coating on leaves caused by the honeydew secreted from scale or aphid infestations.

Many fungal issues begin subtly but can spread across the canopy within weeks. Early detection and prompt pruning of infected limbs can save a tree from decline.

How to prevent summer tree pests and diseases

1. Maintain healthy soil: Mulch with organic material to retain moisture and regulate temperature.
2. Water deeply and consistently: Shallow watering encourages weak roots and stress.
3. Prune for airflow: Reduce dense foliage to lower humidity and fungal spread.
4. Remove debris: Clean up fallen leaves and fruit that may harbour pests or disease.
5. Inspect regularly: Early signs like yellowing leaves or sticky residue indicate problems forming.

If you’re unsure about a pest or fungal issue, our qualified arborists can identify the cause and recommend safe, effective solutions tailored to your trees.

When to call a professional arborist

Homeowners often spot the early signs of trouble but may not know how serious it is. If branches are dying back, bark is peeling, or insects are spreading rapidly, it’s time to call in the experts. At Dawson Tree Services, we handle diagnosis, pruning, and when needed, emergency tree removal to prevent hazards or property damage.

Book your summer tree health check

Keep your garden thriving this summer with expert advice and care. Our team can assess your trees for pests, fungi, and overall health – providing clear recommendations for maintenance or treatment. For a safe, affordable, and professional service, contact us today.

Call (03) 9720 5111 or email ikdawson@bigpond.net.au to arrange your summer tree inspection.