Gumtree bugs

• Adults are brown and shaped like a shield, with ridged shoulders. They are 15–22mm long and winged, and usually move slowly compared to the nymphs.
• Nymphs are wingless, and vary in colour from yellow to orange, blue or light green, with grey markings. Some species have striking patterns.
• Both adults and nymphs have long antennae and long legs. They are often found feeding on new shoots.
• They have powerful sucking mouthparts, or stylets, which they insert into the plant to suck the sap.
• When handled, they give off a pungent odour.

Throughout Australia, particularly in tropical and subtropical regions.

Various eucalypt species, including:

• white mahogany (Eucalyptus acmenoides)
• Dunn’s white gum (E. dunnii)
• southern blue gum (E. globulus)
• rose gum (E. grandis)
• grey gum (E. longirostrata)
• tallowwood (E. microcorys)
• blackbutt (E. pilularis)
• spotted gum (Corymbia maculata)

• Both adults and nymphs suck sap from new shoots, causing tips to wilt and die.
• They prefer coppicing eucalypts to non-coppicing eucalypts.
• They only cause significant damage to trees when in high numbers.

• Eggs are laid in batches of 6–14 on the leaf surface of young, vigorously growing leaves.
• There are 5 instars, and different stages of instars are found on the same tree.
• Gumtree bugs are regularly encountered from December to April and may be found at other times as well.

• Natural parasites of Amorbus eggs include wasps. However, predation and parasitisation of nymphal and adult stages has not been commonly observed, possibly because of their defensive secretions and the aposematic colouring of most nymphal stages.
• Control is not usually required, but hand collection or disruption by sticks can be attempted on young trees.

• 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.
• Kumar, R, 1966, Studies on the biology, immature stages and relative growth of some Australian bugs of the superfamily Coreoidea (Hemiptera: Heteroptera)l, Australian Journal of Zoology, 14(5):895–991, viewed 29 September 2023.
• Steinbauer, MJ, Yonow, T, Reid, IA, Cant, R, 2002, Ecological biogeography of species of Gelonus, Acantholybas and Amorbus in Australia, Austral Ecology, 27(1):1–25.