The pests and pathogens that actually occur here

Why most online disease advice is useless here

Search for tree diseases and you will get apple scab, Dutch elm disease, cedar apple rust, black knot and fire blight. None of those are meaningful problems for a spotted gum in Erina or a paperbark at Toukley. They are northern hemisphere diseases of northern hemisphere trees.

These are the ones that actually turn up on the Central Coast.

Root and soil pathogens

Phytophthora cinnamomi — the most damaging of them. A soil-borne water mould that destroys fine feeder roots, causing progressive crown thinning, dieback from the outer canopy inwards, and eventual death. It thrives in warm, wet, poorly drained soil, which describes a lot of this region's low ground. It is spread in soil and water on boots, tyres and machinery. Once a site is infested it stays infested, so hygiene and drainage matter far more than treatment.

Armillaria root rot — honey fungus. Produces white fungal sheets under the bark at the root collar, black bootlace-like rhizomorphs in the soil, and clusters of honey-coloured mushrooms at the base in autumn. It moves from stump to stump through root contact, which is one genuine argument for full stump removal rather than grinding on an infected site.

Ganoderma and other basal decay fungi — bracket fruiting bodies at the base of the trunk. These indicate established internal decay in the structural root zone, and they are a serious structural concern rather than a health one.

Stem and branch pathogens

Botryosphaeria canker — opportunistic, widespread, and it attacks trees already stressed by drought, waterlogging or root damage. Shows as sunken, discoloured bark, dieback of individual branches, and sometimes gum exudation on eucalypts. Prune out affected wood and, more importantly, fix the underlying stress.

Myrtle rust — established in coastal New South Wales and affecting the Myrtaceae family: lilly pilly, bottlebrush, tea tree, paperbark and eucalypt seedlings. Bright yellow powdery spores on new growth, causing distortion and tip dieback. Mature eucalypts generally cope; highly susceptible species have been hit hard.

Insect pests

Borers — longicorn and other wood-boring beetle larvae. Round or oval exit holes, frass at the base, and sawdust in bark crevices. Borers are overwhelmingly secondary: they attack trees already weakened by drought, root damage or waterlogging. Finding borers means looking for the primary stressor.

Psyllids and lerps — sap-sucking insects on eucalypt foliage, protected under small white sugary coverings. Heavy infestations brown off and drop leaves. Healthy trees recover; stressed trees can be pushed over the edge.

Scale and sooty mould — sap-suckers excreting honeydew, on which black sooty mould grows. The mould is unsightly rather than damaging; the scale is the actual problem, and ants farming them is a common sign.

Palms

Palms on the Peninsula and the coastal suburbs get their own problems. Fusarium and other vascular wilts cause one-sided frond death and are readily spread on unsterilised pruning tools — one good reason not to have palms trimmed by whoever knocks on the door. Palms cannot compartmentalise wounds the way trees do, so damage is permanent.

What matters more than the diagnosis

On most Central Coast blocks the underlying cause is not a pathogen at all. It is root disturbance from building work, soil compaction under vehicles, waterlogging on low ground, or drought stress in the sandy soils. Pathogens and borers move in afterwards.

If a tree is declining, look for what changed around its roots in the last three years before looking for a disease. The dead or dying article covers the assessment, the seasonal checklist covers prevention, and tree removal services covers the outcome when it has gone too far.