Exotic longhorned beetles

ALB and CLB are similar.

Adult

• Typical elongate longhorn beetle shape
• Shiny black with white spots on the back
• Males up to 25mm, females to 35mm
• Antennae longer than body length, with whitish-blue rings
• Males have very long antennae (1.7–2.5 times the body length) compared to females (1.2–1.3 times the body length)

Egg

• Similar to a rice grain, oblong, 5–7 mm long and creamy-white
• Each egg is laid singly in a small depression under the bark of the trunk or branch, or exposed root.
• Eggs turn yellowish-brown prior to hatching

Larvae

• A creamy or yellowish-white, legless grub, with an amber coloured diffuse band behind the head and black mouthparts
• Up to 60mm long and 10mm wide at its broadest point when full grown

Pupae

• Off-white to yellowish in colour with legs and long coiled antennae
• 24–38 mm long
• Pupation occurs in a chamber in the heartwood
• The pupa is usually surrounded by wood shavings

Plant stage and plant parts affected

• All stages of plant growth (seedlings to mature trees) can be affected
• Exotic longhorned beetles can feed on leaves, the plant stem or trunk, branches and roots

Plant damage

Severe infestations of the wood boring larvae can damage the trees vascular tissue, structurally weakening trees. During wind and storm events the affected trees are more likely to drop branches or fall over. The trees are also predisposed to attack by secondary pests or diseases.

Feeding by the adult beetles can cause defoliation and shoot damage. Damage to fruit shoots can cause in a reduction of fruit production resulting in economic loss.

A number of large (greater than 2cm long) native wood boring beetles that are similar to longhorned beetles, occur in Australia. Of these, only Glenea spinifera (13–25mm long), which is dark blue with white spots, could be confused with ALB or CLB. Glenea spinifera, however, does not have the pale antennal rings of ALB or CLB.

ALB and CLB are 25–35mm long, shiny black, with distinctive irregular white spots on their back and white ringed, very long antennae.

Read more about wood boring beetles of trees and timber.

ALB is found on over 30 woody plants species, including alder, apple, ash, birch, elm, maple, mulberry, pear, plane tree, poplar, stone fruit, robinia, roses and willow (CABI, 2019).

CLB can feed on over 100 woody plant species from 26 families. It is a serious pest of fruit trees such as apple, citrus and pear, and alder and plane tree. Native Australian plants such as Acacia decurrens (green wattle), Acacia mearnsii (black wattle), Casuarina equisetifolia and C. stricta (coast she-oak) can also be affected (CABI, 2019).

View a detailed host list for exotic longhorned beetles.

• After emerging from their pupa, the adult beetles emerge from circular holes, 10–20mm in diameter
• They are active during the day, feeding on leaves, petioles and the young bark of host trees.
• Adults usually survive for about a month.
• Egg laying commences a week after mating, usually on susceptible host tree trunks about 60cm above the soil.
• Each female lays around 30–90 eggs, with reports of up to 190 eggs laid, from Japan.
• Eggs are laid singly, under the bark in depressions chewed out by the female.
• Depending on environmental conditions, the eggs hatch after 1.5–2 weeks.
• Larvae initially feed on the inner bark layer in branches and the trunk, moving deeper into the heartwood as they mature.
• As the larvae feed, they form tunnels or galleries in tree trunks and branches. Frass (larval waste products) and sawdust-accumulate at entrance holes and at the base of infested trunks and branches.
• Larvae continue feeding and growing for several months before pupation.
• Pupation occurs in chambers in the heartwood. During this stage, the larvae change into adults.
• Depending on climatic and feeding conditions, there is usually one generation per 1–2 years.

Economic impact

Exotic longhorned beetles have the potential to cause significant damage to a number of tree crops including apple, citrus, pear, stone fruit and tree nut crops. Production nurseries may also be affected. In forestry plantations this pest can cause yield reduction. Timber may be downgraded, reducing its value, and export markets for timber products may be disrupted. Overseas, the cost of removing, treating and destroying affected urban street trees has also been significant.

Environmental impact

Some Acacia and Casuarina species are known to be hosts for CLB. The true host range for exotic longhorned beetle on Australian native species in unknown. Australian native forests and bushland could be impacted.

Long distance pest spread can occur through the movement of eggs, larvae, pupae and adults in woody planting material, such as nursery stock or bonsai plants, or in timber, timber products and wood used in pallets and packaging made of host species.

The adults can fly short distances, allowing the beetles to disperse locally in the search of host plants.

Examine newly imported host plants and timber products and wooden pallets and packaging for:

• insect frass and wood shavings
• larval tunnels, up to 15mm wide, containing whitish grubs up to 60mm long
• round to oval exit holes where the adults have emerged
• live beetles, larvae, pupae or eggs.

If you see this pest or any other pest that you think may have traveled to Australia, contain it where possible and immediately report it to the Exotic Plant Pest Hotline on 1800 084 881.

Find out how farmers can protect their farms from plant pests and diseases.

Visit the farm biosecurity website to find specific biosecurity manuals for fruit and nut crops.

Read the Biosecurity manual for the plantation timber industry (PDF, 1.9MB).

If you think you have found an exotic longhorned beetle, including adults or larvae, you must take all reasonable and practical steps under your control to minimise any associated risks, including reporting it to Biosecurity Queensland on 13 25 23. This is called a general biosecurity obligation (GBO).