Overview of forestry pests and diseases


The following resources contain information about the pests and diseases that affect the forestry industry:

Stem borers

Stem borers are grubs or caterpillars (moth or beetle larvae) that tunnel through and feed on wood, causing damage to twigs, branches, stems and trunks. Stem borers can reduce wood quality in harvested logs and timber. Stem borers include:

Symptoms include:

  • the presence of sawdust (frass)
  • damaged or lifted bark, and ring-barking (girdling)
  • exit holes
  • cracking and swelling
  • leaking sap
  • withered branch tips.


Leaf-chewing beetles and mites feed on tree foliage and can cause extensive damage, especially to young trees. Leaf-chewing insects include:

Symptoms include:

  • jagged or ripped leaf edges
  • reduced leaf area
  • distortion and dieback in young leaves
  • defoliation.


Sap-sucking insects affect trees by removing large quantities of water and nutrients, causing wilted or shrivelled growing tips. Sap-sucking insects include:

Symptoms include:

  • leaf discolouration and withering
  • leaf loss in severe infestations.

Leaf miners and gallers

Leaf miners feed inside the leaf between the top and bottom surfaces. Gall-formers are small wasps or flies that lay eggs between the leaf surfaces where the hatched larvae feed. Leaf mining insects include:

Leaf miner symptoms include:

  • dried, silvery or brown leaf tissue
  • leaves shedding early
  • severe infection can cause defoliation.

Gall-former symptoms include:

  • the tree developing galls, which are swellings in leaf or shoot tissue that surround the eggs and larvae
  • sometimes significant defoliation or tree malformation.

Fungal diseases

Fungal diseases can affect trees by infecting their leaves, stems, bark and roots. Fungal diseases include:

Leaf symptoms include:

  • spots, blotches and blisters
  • powder
  • changes in colour (discolouration)
  • defoliation, particularly in the lower crown.

Stem and branch symptoms include:

  • dying patches
  • bark stains
  • cracks and splits (sometimes with leaking sap)
  • sheets of fungal mycelium (dense strands of fungal threads) under the bark.


The Biosecurity Act 2014 outlines control measures relating to exotic timber pests in Queensland.



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