PEST

NAME
Winter Bronzing
Thaumastocoris species

ORDER
Hemiptera

Description of the Pest
Thaumastocorids bugs are sap sucking insects with a strong proboscis and are shield shape. The adult is dull brown with long anatine and legs, growing to 5mm long. The ovoid black eggs are microscopic size 1mm in length and in time the egg colour remains blackunlike Psyllids eggs that fade. They are laid in groups from 60 to 1,000 on the leaves in clusters up to a 10mm wide. They feed in colonies and cause excessive damage. Both adults and nymphs have piecing and sucking mouthparts and adults commonly shelter under leaves or bark during winter.

           Eggs mag. 274 x
Image by A. Noack

Appearance and Distribution of the Pest
Generally nymphs appear in early winter to winter after hatching from eggs that were laid in late autumn, but the pest may be seen through the year in extreme cases. The adults can fly short distances or further with the assistance of wind, to a new host plant to distribute eggs or feed. This is not a wide spread problem, but an important one in urban areas of Sydney Australia. Other species are found in Tasmania and Western Australia. Colonies of this insect have been recorded in South Africa and are thought to be originating from Australia.

Active insect on leaf

Life Cycle
These insects have a Hemimetabolouslife cycle, ie. When the immature nymphsresemble the adults.
The black eggs hatch within two weeks and there are five nymphal stages before reaching an adult. The origin of the pest is unknown and it has only recently become a pest.

Damage Caused
The sap sucking activities greatly reduces the capability of the leaf to photosynthesise by feeding on the epidermal layer of the leaves. These leaves are then shed, and the repetitive attack on a tree weakens its ability to produce food (starch). Branches and twigs die back and eventually the tree starves to death. Initial symptoms are pale green foliage that turns reddish or bronze. This colour change occurs quickly over a 5 day period and infestations normally occur on a small part of the crown at first. The insects do not produce honeydew
White Stemmed Gum Moth and Winter Bronzing.


Image by A. Noack

Susceptible Plants
Eucalyptus species are the host with certain species most susceptible, such as Eucalyptus nicholii(Narrow Leafed Black Peppermint).
Other species are less severely attacked these include, Eucalyptus bicostata(Southern Blue Gum), Eucalyptus tereticornis(Forest Red Gum), Eucalyptus viminalis(Ribbon Gum), Eucalyptus camaldulensis(River Red Gum), Eucalyptus microcorys(Tallow Wood), Eucalyptus sideroxylon(Mugga Iron Bark) and Corymbia citriodora(Lemon Scented Gum).

Cultural Control
It is very difficult to control this pest using cultural methods, but infested trees can be watered and feed to improve vigour.

BiologicalControl
There is no satisfactory biological control but the Mymarid wasp deposits her eggs in up to 30 Thaumastocorids eggs at a ratio of 1 to 1.

Mymarid wasp next to pin head

Chemical Control
There is no long term solution to infestations, but trees may be injected in extreme cases.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.