Montana Field Guide

The Asian long-horned beetle is a large wood-boring beetle native to eastern Asia. Adult beetles are typically 1.7 to 3.9 cm in length with long antennae 1.3 (females) to 2.5 times body length (males). The elytra is black with 20 irregular white spots. Antennae have contrasting black and white bands. Larvae are large legless grubs, typically white or cream colored.

The species was first documented in North America in 1996 in Brooklyn, New York. Larvae bore under the outer bark of host trees destroying the vascular system and may lead to death of the host. The introduction and spread of this non-native invasive species presents a threat to urban forests and ecosystems where deciduous host trees are a significant member of the plant community. Several genera of native trees are preferred hosts including Acer, Populus, and Salix (Rose 2014) are important components of Montana’s ecosystems, so establishment of this species within Montana could have severe impacts.

The phenology of this species has not been established in Montana. In its native range generation time varies with climactic conditions with a significant latitudinal correlation. Development from egg to adult beetles typically takes 1 or 2 years. The species most commonly overwinters as a larvae, although overwintering as eggs and pupa also occur (reviewed in Hu et al . 2009).

Adults emerge in the spring and summer. Males are sexually mature at emergence, while females can copulate at this time they require a feeding period before they reach maturity. Both males and females mate with multiple partners. In its native range females lay between 25 and 40 eggs (Li and Wu 1993) although fecundity may be higher in North America with 30 to 178 eggs recorded (Kenna 2006). Eggs are deposited singly in oviposition sites within the bark of host trees. Eggs hatch in approximately two weeks. Larve feed on the decayed phloem surrounding the oviposition sites and eventually move from feeding on the phloem/ cambium to the xylem. After progressing through five instars, the larvae pupates then emerges as an adult (reviewed in Hu et al. 2009).

Within its introduced range in North America, this beetle is distinct. The large size, long antannea, and irregular white spots on the elytra make this species distinct from other beetles. Native species of longhorn beetles (Cerambycidae) do exist in Montana, however most are much smaller and those similar in size to the Asian long-horned beetle differ in the coloration of the elytra.

Deciduous forests. This species uses deciduous trees as hosts, and while some genera are preferred, the species is somewhat of a generalist in its host preferences (see Food comments sections below).

Five genera of trees have been identified as href="https://www.aphis.usda.gov/plant_health/plant_pest_info/asian_lhb/downloads/hostlist.pdf" target="_blank"> preferred hosts in the US by APHIS. Acer (maples and boxelder), Aesculus (horsechestnut, buckeye), Betula (birch), Salix (willow), and Ulmus (elm). Species representing all but Aesculus occur in Montana’s native ecosystems, and all may be used in landscaping in urban areas. Two genera Fraxinus (ash) and Populus (cottonwood) have species which serve as occasional or rare hosts, but are important components of Montana ecosystems. As the species has not yet been introduced into western areas of the US, host species that are found only in this region or area rare in occupied areas have not yet been exposed and their suitability as hosts has not yet been observed.

Known populations of the Asian Longhorned Beetle are subject to ongoing eradication efforts. Once the species is detected in an area, eradication strategies including host removal and chemical treatment combined with intensive survey effort are typically employed.
Montana and other states are at risk for establishment primarily through the transport of wood and wood products harboring the organism.

For information and resources on plant pests and diseases see the USDA's Animal and Plant Health Inspection Service's Plant Pests and Diseases Profiles