Winter bronzing bugs

• Adults are small (2–3mm long) and brown to orange-brown. They are long and flat.
• When adults are seen under a hand lens, their eyes on broad 'stalks' are visible.
• The nymphs of Thaumastocoris peregrinus are flat and orange with black spots on the thorax and abdomen.
• Adults and nymphs often feed on the same leaf and display erratic behaviour when disturbed. Adults may run quickly and unpredictably, often moving to the other side of a leaf or another surface.

• Throughout Queensland, mainly east of the Great Dividing Range

• Spotted gums (Corymbia citriodora subspecies variegata, C. citriodora subspecies citriodora, C. maculata and C. variegata)
• Black wattle (Acacia cunninghami)
• Dunn's white gum (Eucalyptus dunnii)
• Southern blue gum (E. globulus)
• Rose gum (E. grandis)
• Tallowwood (E. microcorys)
• Blackbutt (E. pilularis)
• Sydney blue gum (E. saligna)
• Red ironbark (E. sideroxylon)
• Forest red gum (E. tereticornis)

• Adults and nymphs are sap feeders, extracting nutrition from leaves.
• The bugs inject enzymes into leaves while feeding to help their digestion, causing red-brown ‘bronzing’ of leaves.
• They most often affect fully expanded, mature foliage of spotted gums, usually in the middle to upper canopy. The north to north-eastern side of the canopy is usually first affected.
• Symptoms appear from May to September.
• Severely affected leaves have reduced photosynthetic capacity and are shed prematurely. This can lead to partial or complete defoliation.
• In some cases, infestation leads to branch dieback or tree mortality.

• Females produce around 60 eggs, which take 4–8 days to hatch.
• Eggs are laid singly or in clusters on leaves and stems.
• They are 0.5mm long and 0.2mm wide, relatively large for the size of the female.
• The lifecycle is 30–60 days. It consists of 5 nymphal instars and an adult phase.
• Several generations can be produced each year, particularly when there are optimum conditions for growth and survival.

• Natural predators include parasitic wasps, lacewings and birds.
• The most effective biological control agent for T. peregrinus is the minute mymarid wasp Cleruchoides noackae.
• Systemic chemical injection may be an option in severe infestations. In Australia the chemical control option for T. peregrinus is Imidacloprid, applied via systemic injection into tree stems. This can provide effective control for a small number of trees. However, on a commercial scale this method is not economical, as it is time-consuming and costly.
• Aerial spraying is ineffective because the highest densities of bugs occur in the middle canopy, which cannot be reached by aerial sprays.

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.

Noack, AE, 2009, The taxonomic revision of the genus Thaumastocoris and the biology and chemical control of the eucalypt pest Thaumastocoris peregrinus (Heteroptera: Thaumastocoridae) [dissertation], University of Sydney, NSW.

Noack, AE, Rose, HA, 2007, Life-history of Thaumastocoris peregrinus and Thaumastocoris sp. in the laboratory with some observations on behaviour, General and Applied Entomology, 36:27–33.