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Number 13
Revised May 1993
By Charlma Phillips, Principal Forest Health Scientist

Coreid bugs are large insects, belonging to the bug family Coreidae, which feed on the soft tissues, particularly new shoots, of the host plant. They have powerful sucking mouthparts (stylets) which they insert into the plant to suck the sap.

There are many species, but not all feed on eucalypts. Two that are found on eucalypts are Amorbus spp. and Gelonus spp. These are solitary insects, which are mainly active in warm to hot weather.
They are generally regarded as minor pests but since the establishment of eucalypts in plantations, they have become more noticeable - especially in plantations containing the ash species of eucalypts, such as Eucalyptus obliqua and E. regnans.

The adults are relatively slow moving and are seen on the tips of shoots. Nymphal stages are fast moving.

Coreid bugs emit a strong unpleasant odour and may eject a foul smelling liquid when disturbed. This behaviour is a deterrent to many would-be predators.

Description

Amorbus spp. are also known as eucalyptus tip bugs. They are stout shield-shaped bugs, 15-22mm in length. The adults of A. alternatus, are black in colour, with yellow on the wing covers and a short spine on each shoulder. The nymphs of this species are very brightly coloured, blue and orange. Adults of A. obscuricornis are dark brown in colour (pictured below). The males have thickened hind legs with large spines. The first two nymphal instars are green and black and the last three are orange and black.

Gelonus tasmanicus adults are dark brown/black in colour with white on the legs and antennae (pictured below). They are approximately 13mm in length. Nymphs are dark brown in colour.

Coreid eggs are large and oval in shape. In some species they are bright green and in other species they are brown.

Life History

Coreid bugs are found on eucalypts during spring, summer and autumn, ie from October to April. They are mainly active on warm to hot sunny days and are rarely seen in wet or windy conditions. Nymphs may be present from November. There is one generation per year. Eggs are laid singly on the leaf surface of shoot tip, though there may be several eggs laid close together. There are five nymphal instars.

Eggs of two different species of Coried bugs

 
Nymphs of different species of Coried bugs

Damage

Amorbus obscuricornis and Gelonus tasmanicus have caused damage in Tasmania in eucalypt plantations containing ash species. Minor tip damage has also been reported on E. globulus and the potential exists for these bugs to cause significant damage in E. globulus plantations if number become sufficiently high.

Feeding by Coreid bugs causes wilting of new shoots and subsequently dieback of these shoots. The bugs inject a toxic saliva into the plant during feeding which causes breakdown of the leaf tissue and ultimately death of the leaf. Heavily attacked trees - particularly young trees - appear stunted.
A white sticky substance that attracts ants is often found on shoots where bugs have been feeding.

Control

Control of Coreid bugs in E. globulus plantations is usually not warranted. In situations where chemical control is necessary, a synthetic pyrethroid, cypermethrin, is the recommended chemical.
Natural control includes birds, spiders, scorpions, assassin bugs, tachinid flies and chalcid wasps.

Summary

When to look: From October to April, on warm to hot sunny days.

Where to look: On shoot tips.

What to look for:  Look for wilted or dead tips on shoots
Look for large black or brown bugs
Look for brown or brightly coloured nymphs

For further information contact PIRSA Forestry

Disclaimer: While this publication may be of assistance to you, the government of South Australia and its officers do not guarantee that it is without flaw of any kind or is wholly appropriate for your particular purpose. The Government therefore disclaims all liability for any error, loss or other consequence that may arise from you relying on any information in this publication.