Tree Pests and Diseases in Perth WA and how to Identify and Treat Them
Updated: 14 hours ago
Trees are a vital part of Perth’s natural landscape, providing shade, improving air quality, and enhancing the beauty of properties.
However, tree pests and tree disease can threaten their health, leading to significant damage or even tree loss.
Knowing how to identify and treat these issues is essential for maintaining a healthy garden or property.
In this guide, we’ll explore common tree pests and diseases in Perth WA and how to treat them.
Trees affected by pests or diseases often show early warning signs before serious damage occurs. In Perth, common symptoms include yellowing leaves, dead or dying branches, holes in the bark, unusual fungal growth and a thinning canopy.
Perth's hot, dry summers and sandy soils can place additional stress on trees, sometimes making pest infestations and disease symptoms more noticeable.
However, not every unhealthy-looking tree is suffering from a pest or disease. Water stress, poor drainage and root damage can produce similar symptoms.
Regularly inspecting your trees can help identify potential problems early. If you notice significant branch dieback, trunk damage or signs of instability, arranging a professional tree assessment can help determine whether pruning, treatment or removal may be necessary.
Common Tree Pests and Diseases in Perth WA and How to Treat Them
1. Termites in Trees
Signs: Hollow trunks, weakened branches, and mud tubes on the bark.
Treatment: Yes, you can treat a termite infestation in trees, but success depends on how advanced the infestation is.
Some termite species, like Coptotermes acinaciformis, are highly destructive and may require professional treatment.
How to Treat a Tree Termite Infestation in Perth
1. Identify the Termite Species
Subterranean termites (Coptotermes, Mastotermes) – The most destructive; they build mud tubes and attack both trees and buildings.
Dampwood termites (Porotermes, Stolotermes) – Usually found in dead or rotting trees.
Arboreal termites (Nasutitermes) – Less damaging; build mud nests in trees.
2. Treatment Methods
Treatment depends on the termite species, the extent of the infestation and the condition of the tree. A licensed pest control professional can inspect the infestation and recommend suitable treatments, which may include baiting or other approved termite management methods.
Where termites have caused significant internal decay or weakened the tree's structure, a professional tree assessment may be necessary to determine whether pruning or removal is the safest option.
Removing dead wood and maintaining good tree health can also help reduce conditions that favour some termite species.
When to Call a Professional in Perth?
If the infestation is large or near buildings
If you see mud tunnels leading from the tree to your home
If you discover termite activity and are unsure about the extent of the infestation, particularly if the affected tree is close to buildings.
There are many professional tree surgeons in Perth WA who will be able to inspect your affected tree and advise on whether it would be best to treat it or whether a tree removal service would be the most effective approach.
2. Aphids on Trees
Signs: Sticky leaves, black sooty mould, and stunted growth.
Aphids thrive in Perth’s warm climate, especially during spring and summer. You may also notice ants crawling up and down the trunk, as they are attracted to the honeydew aphids produce.
If left untreated, aphids can weaken trees, making them more susceptible to drought stress and disease.
Treatment: Neem oil and insecticidal soaps can help control aphids when applied correctly. However, these treatments may also affect beneficial insects through direct contact, so always follow the product instructions and avoid spraying when pollinators are active.
In Perth gardens, a strong spray of water can also dislodge aphids from the leaves.
Regularly pruning affected areas and maintaining healthy soil can further reduce the risk of infestations.
Researching tree pests specific to Perth’s climate is crucial. Some tree species, like citrus and ornamental trees, are particularly vulnerable to aphids.
Understanding the best organic solutions suited for WA’s conditions—such as drought-resistant companion planting or eco-friendly sprays—can make pest management easier.
Avoid chemical pesticides that can harm native wildlife and beneficial insects like bees.
With the right knowledge and preventative measures, you can keep your trees healthy and aphid-free all year round.
3. Borers in Trees
Signs: Small holes in the bark, sawdust-like frass, and branch dieback.
Treatment: The appropriate treatment depends on the borer species and the extent of the damage. Pruning affected branches may help in some cases, while more serious infestations require professional assessment. Chemical treatments should only be considered once the pest has been correctly identified and a suitable approved treatment is available.
How to get rid of pests in trees naturally? Maintaining tree health is the best defense against borers. Healthy trees can resist infestations more effectively.
Regular watering (especially during Perth’s dry summers), mulching, and using organic fertilizers can strengthen trees and make them less vulnerable.
Removing dead wood and avoiding unnecessary wounds to the bark also help prevent borers from gaining access.
If you have native trees like jarrah or marri, be extra vigilant, as they can attract specific borer species in WA’s climate.
Polyphagous Shot-Hole Borer in Perth: This invasive pest can cause serious damage to trees by boring into the wood and introducing harmful fungi. Warning signs may include tiny holes in the bark, staining, branch dieback and declining tree health. Suspected infestations should be reported to WA's Department of Primary Industries and Regional Development (DPIRD). Always follow current biosecurity requirements when handling or disposing of affected wood.
4. Scale Insects on Trees
Signs: Bumps on twigs, yellowing leaves, and honeydew secretion leading to mold growth.
Treatment: Horticultural oil or insecticidal soap works well against scale infestations.
5. Root Rot in Trees
Signs: Wilting, yellowing leaves, and soft, decayed roots.
Treatment: Improving soil drainage and avoiding excessive watering can help manage some forms of root rot. However, treatment depends on the underlying cause. Root diseases caused by pathogens such as Phytophthora can be particularly serious, and severely affected trees may not recover. A professional assessment can help determine whether the tree can be managed safely or requires removal.
Where root rot has severely damaged a tree's root system and affected its stability, professional tree removal may be necessary to protect nearby people and property. Swift Trees Perth provides experienced tree removal services throughout Perth WA.
6. Powdery Mildew on Trees
Signs: White, powdery fungal growth on leaves.
Treatment: Prune affected areas and use fungicides.
DIY tree pest control that works includes increasing airflow around trees.
7. Canker Disease in Trees, Perth WA
Signs: Canker disease presents as sunken, cracked lesions on the bark, often oozing sap.
Over time, the affected branches may wither and die, especially during hot summers.
Some native species, such as eucalypts and banksias, are particularly vulnerable.
Causes in Perth’s Climate:
Hot, dry summers can stress trees, making them more susceptible.
Wounds from pruning or storm damage provide an entry point for fungal and bacterial infections.
Fungal pathogens such as Botryosphaeria species can contribute to canker diseases, particularly in stressed trees. Other pathogens, including Phytophthora species, are associated with root diseases and dieback in Western Australia rather than being typical causes of bark cankers.
Treatment & Management:
Pruning: Remove affected areas in dry weather to prevent further infection, and sterilize pruning tools between cuts.
Fungicides: Chemical treatment is not always effective against canker diseases. Identifying the cause of the infection is important before considering fungicides, and severely affected branches may need to be professionally pruned or removed.
Watering & Mulching: Perth’s sandy soils drain quickly—deep, infrequent watering and organic mulch can reduce stress.
Avoid Wounds: Minimize pruning in summer when trees are already stressed, and protect trunks from mechanical damage.
Choose Resistant Species: If planting new trees, select drought-hardy, disease-resistant species suited to Perth’s climate.
When Should a Diseased Tree Be Removed in Perth?
Not every tree affected by pests or disease needs to be removed. Many trees can recover with appropriate treatment, improved growing conditions or selective pruning.
However, tree removal may be necessary when extensive decay, serious structural damage or advanced disease makes a tree unsafe.
Signs that a tree may require professional attention include:
Large dead branches that could fall unexpectedly.
Significant decay or cavities in the trunk.
Extensive root damage affecting stability.
A sudden lean or visible movement around the roots.
Widespread branch dieback or canopy deterioration.
If you're concerned about a damaged or diseased tree, Swift Trees Perth provides professional tree removal services in Perth. An assessment can help determine whether removal is appropriate.
How to Prevent Tree Pests and Diseases in Perth
Proper Tree Care Practices: Regular pruning, watering, and fertilization keep trees healthy.
Routine Inspections: Identifying issues early prevents severe damage.
Tree Pest Prevention Tips: Use mulch and organic sprays to deter insects.
Expert Assistance: Consult tree health management services to detect and prevent pest and disease problems before they escalate.
Identifying tree pests and diseases early can help protect the health and appearance of your trees. Regular inspections, appropriate pruning and good tree care practices can reduce the risk of serious damage.
If your tree has extensive dead branches, visible decay or signs of structural instability, Swift Trees Perth can assist with professional tree pruning and removal services throughout Perth and surrounding suburbs.
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