Gardeners are likely to become aware of the presence of these longhorn beetle either when they notice the adult beetle or find exit holes near the base of infested trunks or exposed roots with citrus longhorn, while exit holes of Asian longhorn can be much higher up a tree in the trunk or branches.
- Citrus longhorn beetle is a large (21-37mm long) black beetle with white markings on its wing cases
- The antennae are particularly distinctive because they are up to twice the length of the body and are black with white/light-blue bands
- The Asian longhorn beetle is very similar in size and appearance
- Some native (non-pest) longhorn beetles have banded antennae but they are not black with white spots
- The legless larvae are creamy white with pale brown heads and are up to 56mm long
The larvae of citrus longhorn beetle make tunnels in the lower trunk and roots of host plants for two years or more. There may be no external signs of infestation until the adult beetle emerges, leaving a circular exit hole 6-11mm in diameter. These are typically found near the base of trunks or on exposed roots. Larvae of Asian longhorn beetle develop higher up in the trunks and branches of many deciduous trees. The tunnels created by the larval feeding make trees susceptible to diseases and wind damage. The adults cause limited damage by eating foliage and young bark.