Giant pine scale

Giant pine scale (Marchalina hellenica) is an insect that sucks the sap of pine trees, posing a threat to our softwood plantation industry.

Background

Giant pine scale is native to the eastern Mediterranean region, and is known to occur in Crete, Georgia, Italy, Russia and Turkey.

It was detected in 2 states in Australia in 2014 but has not been found in any pine plantations. The affected species included:

  • aleppo pine (Pinus halapensis)
  • stone pine (Pinus pinea)
  • radiata pine (Pinus radiata)
  • blue spruce (Picea pungens).

In Victoria, giant pine scale developed in more than 4,000 infested trees. Such large numbers could not be effectively eradicated, but it has been contained to prevent further spread.

Surveillance

The Australian Forests Products Association funded giant pine scale surveillance in 2021 for SA. This was undertaken in the areas around North Adelaide, Dernancourt and Highbury, where the pest was previously detected. At this time, the surveillance did not find any giant pine scale.

Following a detection in the Hope Valley and Highbury area in July 2023, PIRSA is working closely with local government and the forestry industry to determine if it has spread further.

Residents, gardeners and arborists are reminded to:

  1. Look for signs of the pest on the trunks and canopy of trees.
  2. Report anything suspicious to the Exotic Plant Pest Hotline.
  3. Maintain hygiene practises to stop the spread and fence off affected trees to avoid contamination.
  4. Seek advice from your local council, pest controller, or arborist to determine suitable control options for your trees.

Impacts

The insect feeds exclusively on plants from the family Pinaceae, such as pines, firs and spruces. Trees that look similar to hosts species but are not affected by this pest include cypress pines, hoop pines and she-oaks.

Once established, giant pine scale causes defoliation, branch dieback, gradual desiccation, and tree death.

This pest is slow to spread without human intervention. It travels long distances through movement of infested wood, mulch and machinery, or on animals and birds.

High-risk pathways from an infested site are areas of public congregation, and places commonly attended by travelling visitors, such as parks, ovals, golf courses, camping grounds, walking or bike trails.

Management

Tree removal is the only permanent and effective treatment option for giant pine scale.

Residents and landholders

Following detection, you can manage giant pine scale contamination before your affected trees are removed. To reduce the spread:

  • keep fallen or cut tree branches on your property
  • cut infested branches that hang over the house or structures like sheds, tanks, swings and fences
  • do not park under or near infested trees
  • prevent twigs, cones or leaves falling onto equipment that may be moved (e.g. trailers, trucks and caravans)
  • dispose of unwanted tree branches, needles and pinecones using your green waste bin
  • avoid transporting waste to council transfer station, or if unavoidable, bag or cover waste during transport
  • clean all plant material off gardening equipment using a solution of 80% methylated spirits to 20% water, and a brush or paper towel.

Contractors working with infested trees

When working on infested trees, plant and equipment hygiene are important to avoid spreading giant pine scale to other properties. Follow these steps:

  1. Develop a comprehensive biosecurity plan for removing trees, including hygiene, transport, containment, decontamination and disposal. Consider each step and its possible risk of spreading the pest further.
  2. Talk with the local council about decontamination options and car wash sites for large pieces of equipment.
  3. Cover all loads during transport.
  4. Cover stumps or exposed roots that are not removed with plastic (solarisation) to seal in the insects. Leave in place for at least one summer period to allow the stump or roots to dry up and starve the insect.
  5. Following tree or stump removal, cover the area in a heavy mulch at least 100mm thick. Remaining tree roots close to the surface can become infested and will remain an active feeding site for up to 6 months, while the tree dehydrates and dies.
  6. Keep a hygiene kit handy, containing paper towels, solution of 80% methylated spirits to 20% water, a bristle brush, disinfectant wipes, plastic bags, and spare clothes.
  7. Clean and decontaminate equipment between trees using the methylated spirit solution or disinfectant wipes. Use a multi-purpose disinfectant such as Virkon S, in foot baths and to disinfect non-sensitive equipment.
  8. Clean and decontaminate your machinery, tools and clothing, or change into spare clothing, before leaving the site.
  9. Avoid working on jobs with host pine trees immediately after removing infested trees, for up to 2 weeks where possible.

If you are working with host trees that have no known infestations, it is vital to employ industry hygiene best practices. This is important when moving between states and regions within South Australia.

Identification

Giant pine scale produces a dense, white, cotton-like wax secretion in between the tree bark. It prefers the lower part of the tree, both on the trunk and branches, but may travel into the canopy and on exposed roots.

The extent of infestation can be estimated by the amount of exudate on the tree. Up to 10 spots can be caused by crawlers that have established in the first year, at the base of the trunk where no other infestation point is present.

Hundreds or thousands of spots around the trunk and over a third of the tree are seen in the second year, following adults producing eggs.

Exudate extending up most of the tree and into the branches is seen in the third and fourth year. Beyond this, most of the tree including the canopy will be covered in exudate and it may travel to neighbouring trees.

Lifecycle

The lifecycle of giant pine scale is 12 months. The eggs hatch in September to December, and the first instar produced is a crawler less than 1 millimetre in size. This is followed by a second immature instar which may be found crawling over the tree to find new feeding sites.

The third and final adult instar is bright yellow and can grow to 12 millimetres in length. Adult females do not have wings and carry up to 400 eggs in their bodies. The winged males are rarely seen.

Trunk of a giant pine tree with sections covered by the white scale
Trunk of a giant pine tree with sections covered by the white scale
Adult giant pine scale insects on a pinecone
Adult giant pine scale insects on a pinecone

More information

Exotic Plant Pest Hotline

Suspected plant diseases, exotic pests, or noxious weeds must be reported immediately.

Call us if you find plant pests or diseases that could be a national threat, even if you are unsure. This can be done anonymously.

24 hours a day, 7 days a week

Freecall 1800 084 881
Page last reviewed: 27 Feb 2024

 


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