Gumtree scale

• Gumtree scale insects form large colonies. Their small capsules cluster on stems, branches and leaves.
• They are pink, red, purple, green or brown. When squashed, they release a reddish-brown fluid.
• Capsules are 2–4mm in diameter, reddish to white, and waxy, leathery or cottony. They have a small opening that allows newly hatched nymphs to emerge.
• The insects feed under the capsules and may secrete a white cottony substance.
• Leaves are often sticky from the honeydew excreted by the insects.
• Sooty mould is often found with gumtree scale, turning leaves and branches black.
• Ants are also commonly found with gumtree scale, feeding on the honeydew. They help to protect scale insects from predators and parasitoids and may move individuals to new feeding areas.

• Widespread in Queensland, from temperate to subtropical regions

• Spotted gum (Corymbia citriodora subspecies variegata)
• Southern blue gum (Eucalyptus globulus)
• Rose gum (E. grandis)
• Blackbutt (E. pilularis)
• Swamp mahogany (E. robusta)
• Forest red gum (E. tereticornis)

Stressed trees are more susceptible to infestation.

• The insects suck sap from trees, causing defoliation, especially on the lower and inner canopy of young trees.
• Scale can affect overall tree form and development, especially of small or stressed trees.
• It can weaken host trees and can be a significant pest in establishing eucalypt plantations.
• Heavy infestations can kill trees.
• Sooty mould, which grows on the honeydew, can affect photosynthesis by covering the leaves.

• Scale colonies frequently consist of insects in various stages of development.
• Each year, 2 to 5 generations are produced, depending on the temperature.
• Females lay eggs under their capsules. After hatching, the young nymphs (crawlers) emerge through the opening and begin feeding and developing at a new site.
• Crawlers are dispersed on wind currents, or as passengers on birds or ants.
• Females often lose their legs and remain under their covering until death.
• Adult males are small, mobile winged insects.

• Gumtree scale insects have a wide range of natural predators including small birds and predatory insects (such as assassin bugs, lacewings, hoverflies, ladybird beetles, moths, flies and wasps).
• Small infestations can be removed from the branch and squashed. Alternatively, branches can be removed and burnt.
• Heavy infestations can be controlled by spraying or systemic stem injections.

• Australian Pesticides and Veterinary Medicines Authority (APVMA)
• Carnegie, AJ, Lawson, SA, Smith, TE, Pegg, GS, Stone, C, McDonald, JM, 2008, Healthy hardwoods: a field guide to pests, diseases and nutritional disorders in subtropical hardwoods, Forest & Wood Products Australia, Victoria.
• Hoy, JM, 1963, A catalogue of the Eriococcidae (Homoptera: Coccoidea) of the world, New Zealand Department of Scientific and Industrial Research Bulletin, 150:1–260.
• Jones, DL, Elliot, WR, Jones, SR, 2015, Pests, diseases, ailments and allies of Australian plants, Reed New Holland Publishers Pty Ltd, Chatswood, NSW.