Aphids, mealybugs and scales are common sap‑sucking pests that weaken plants by feeding on new growth and producing honeydew, which can lead to sooty mould. Symptoms include yellowing leaves, distortion, wilting, and in severe cases, leaf drop. These pests often hide on leaf undersides and can spread rapidly in warm conditions.
Management: Remove host weeds, maintain healthy plants, encourage beneficial insects, and use horticultural soaps or oils (avoid use above 32°C). Low‑toxicity chemicals such as imidacloprid or acetamiprid may be used for persistent infestations.
Pictured above: Citrus mealybug.
Chilli thrips are tiny sap‑sucking insects that cause scarring, leaf curl, dried shoots, and deformed flowers. They hide deep within foliage and are active through spring, summer and autumn, especially in humid weather.
Management: Regular monitoring, pruning affected growth, blue sticky traps, horticultural soaps/oils, or targeted chemicals (e.g., spinetoram). Natural predators such as predatory mites and parasitic wasps assist in control.
Pictured above: Chilli thrip infestation on a rose bush stem.
Citrus gall wasp affects citrus trees by forming distinctive woody galls that weaken branches and reduce fruit production. Adult wasps emerge in spring and lay eggs under the bark of new shoots.
Management: Prune out new galls between February–June and dispose of pruned material correctly. Avoid over‑pruning, which encourages susceptible new growth. Oils or horticultural glue may help deter egg‑laying.
Pictured above: Infographic on the life cycle of a Citrus gall wasp.
Citrus leaf miner larvae burrow into new citrus leaves, leaving silver squiggly trails and causing leaf distortion. While rarely fatal, infestations can stunt growth and reduce fruit yield.
Management: Prune affected leaves, encourage natural predators, and apply horticultural oil to deter egg‑laying. Oils do not kill larvae already inside leaves.
Pictured above: Citrus leaf miner affected leaf.
Citrus stink bugs (bronze‑orange bugs) feed on sap, causing wilting, flower drop, and fruit damage. They release a strong odour when disturbed.
Management: Regular inspections, physical removal, companion planting (e.g., marigolds), encouraging beneficial insects, and using pyrethrum‑based sprays when necessary.
Pictured above: Citrus stink bug on the stem of a tree.
Phytophthora dieback is a serious soil‑borne disease that kills plants by infecting their root systems. It spreads through water, soil movement, footwear, vehicles, and contaminated materials.
Management: Clean footwear/equipment before entering bushland, minimise soil disturbance, and use phosphite treatments where appropriate. Public awareness is essential to prevent spread.
Pictured above: Dieback affected area of bushland.
European house borer is a destructive pest of untreated pine and coniferous timbers, capable of causing severe structural damage. Larvae can live inside timber for years, tunnelling through wood.
Management: Follow Restricted Movement Zone rules, avoid storing untreated pine outdoors, and have timber inspected by accredited pest controllers. Report suspected infestations promptly.
Pictured above: European house borer larvae next to a 5 cent coin.
Botrytis gray mould affects a range of legumes and crops, thriving in cool, wet, humid conditions. It causes leaf lesions, defoliation, gray mould, and pod rot.
Management: Use resistant varieties, practise crop rotation, avoid early sowing, maintain paddock hygiene, and apply fungicides when conditions favour disease development.
Pictured above: Gray mold on tree leaves.
Palm leaf beetle is a quarantine pest that attacks young palm fronds, causing brown, scorched‑looking damage. Larvae feed inside unopened spear leaves, making early detection critical.
Management: Report sightings outside Broome, monitor palms regularly, and follow biosecurity guidance for palm material movement.
Pictured above: Leaf beetle on a palm frond.
Queensland fruit fly is a major horticultural pest that attacks many fruit and vegetable crops. Adult flies lay eggs under the skin of ripening fruit, and larvae feed inside, causing soft patches, internal breakdown, and premature fruit drop. Qfly spreads quickly in warm conditions and can rapidly infest home gardens if not managed early.
Management: Inspect fruit regularly, remove fallen or infested fruit, and use bait traps, netting, or exclusion bags. Good garden hygiene and monitoring during peak seasons are essential.
Pictured above: Queensland fruit fly on a leaf.
White cedar moth caterpillars appear seasonally in large numbers on white cedar trees (Melia azedarach). They can cause significant defoliation, stripping leaves during warmer months. Trees generally recover, but repeated heavy infestations may cause stress. Caterpillars may also wander from host trees, becoming a nuisance around homes.
Management: Monitor trees during peak seasons, remove caterpillars or affected foliage, encourage natural predators, and use horticultural oils or low‑toxicity treatments for larger outbreaks.
Pictured above: White cedar moth.
The Department of Primary Industries and Regional Development (DPIRD) is Western Australia’s lead agency for biosecurity, and the management of land and aquatic resources. DPIRD regulates and supports the State’s agriculture, food industries, fisheries, and regional development.
Further information on known pests and diseases can be found on the DPIRD website: https://www.dpird.wa.gov.au/businesses/pests-weeds-and-diseases/animal-pests-diseases/pest-insects/
DPIRD also operates the Pest and Disease Information Service (PaDIS), which provides advisory and identification services for animal and plant pests, weeds, and diseases that impact Western Australia’s agriculture and food sectors.
Pest and Disease Information Service (PaDIS)
Phone: +61 8 9368 3080
Email: padis@dpird.wa.gov.au
Website: https://www.dpird.wa.gov.au/businesses/biosecurity/pest-and-disease-information-service-padis