The Asian Longhorned beetle, Anoplophora glabripennis, is wood-boring beetle that is invasive to the United States. It is capable of devastating populations of urban trees and forests. It is able to attack seemingly healthy trees from multiple generations. Early detection can help prevent infestations from becoming unmanageable.

About Asian Longhorned Beetles

Asian Longhorned beetles are form the family Cerambycidae, or longhorned beetles. They are identified by their long antennae, (up to 2 times the length of the body). The genus Anoplophora is made up of 36 species, all native to Asia. In Asia, it is also known as the Starry Sky Beetle, Basicosta white-spotted longicorn beetle, or smooth shoulder-star longicorn beetle. Asian longhorned beetle has become the commonly used name in North America.

Asian Longhorned Beetle Life Cycle

Adults

Asian Longhorned Beetles adults are between 17-39 mm in length. Females are typically larger than males, but variation can occur in size between both sexes. The antennae are large, segmented and the color alternates between white and black bandings. The tarsi are blue in color and the pronotum have two large spines. The elytra are shiny and black, with white or tan/yellow spots.

While adult females are typically larger than males, their antennae are shorter. Both males and females have white hairs on the upper side of each antennomere, but the black sections appear larger on males, because of the longer antennae.

Adults are least active in the morning, and usually remain in tree crowns until later int the days. Adults feed on lead petiole and bark on small branches, as well as tree cambium. Males can mate multiple times with multiple females. Adults prefer to stay on the host where they were born, if there are enough resources,  but will move for feeding or finding a mate.

Eggs

Adult females chew into the bark before oviposited a single egg under the bark. Oviposition usually occurs on branches or the main trunk. The female also deposits a compound which surrounds the egg and prevents it from being destroyed during the callus tissue formation the tree undergoes to heal the wound. 

Eggs are 5-7 mm in length and look like a large grain of rice. Sap will often ooze from oviposition and the oviposition pits are red or light brown, before darkeing. Egg development is regulated by temperature.

Eggs and first instar larvae are the most vulnerable stage, especially to extreme temperatures or natural enemies. Sometimes eggs that are laid to late in the season, in late summer or fall, do not have enough time to hatch, and these eggs overwinter before resuming development in the following year.

Larvae

Asian Longhorned Beetle larvae have cylindrical bodies and no legs and appear similar to other cerambycid larvae. They are segmented, elongate and can be white or light yellow. Larvae have large black mandibles that hey used to feed under bark before boring into the tree. Larvae excrete frass as they tunnel into trees. Larval development timing is dependent on temperature and host species.

Pupae

Asian Longhorned beetles pupate after sufficient feeding and development. Pupal chambers are about 1 cm below the bark. Pupae look similar to larvae but they begin to darken during metamorphosis.

Predicting life cycle progression

Asian Longhorned Beetle life stage progression timing is regulated largely by temperature. The Asian Longhorned Beetle growing degree day model can be used to predict the timing that adults will emerge, based on local temperature data.

The Asian Longhorned Beetle Emergence Growing Degree Day model uses a lower threshold of 50F and an upper threshold of 95F . It can be calculated with daily high and low temperatures, using the sine model to estimate growing degree day units, or the Pest Prophet app can be used to calculate GDD accumulation from hourly temperature data for a specific field. 

Using Jan. 1st as a default “biofix” date, or starting point for accumulation, the overwintered larvae begin pupation at about 533 GDD (F). The first adult emergence occurs at approximately 757 GDD (F), peaking at about 1551 GDD (F). 

Similar Looking Beetles

The citrus longhorned beetle is a closely related species that appears similar to Asian Longhorned beetles, but it can be distinguished by black scutella and smooth elytra.

Pine sawyers are also commonly mistaken for Asian Longhorned Beetles. These have no markings on their elytra, however, and they usually emerge earlier in the season than Asian Longhorned beetles. The cottonwood borer is also commonly mistaken for Asian Longhorned Beetle. It can be identified by it’s black spots and yellow-white body.

Asian longhorned beetle larve look very similar to larvae of other species of cerambycids. There are not a lot of distinguishing characteristics. Using coloration of larvae can be helpful in identifying Asian Longhorned Beetles, but sometimes genetic tools are needed to successfully identify larvae to species.

Asian Longhorned Beetle Distribution

The Asian Longhorned Beetle was discovered in the United States in 1996 in Brooklyn, New York, but was found in nearby areas soon after. In 2013, Asian Longhorned Beetle was discovered in Canada. Infestations have also been discovered in most of central and western Europe. It is broadly spread through China and North and South Korea. And has also been found in Japan.

Proximity to major transportation hubs and availability of preferred hosts are the two major factors in predicting risk of Asian Longhorned Beetle infestation in a given area. Asian Longhorned Beetles also have really high tolerance for cold weather, with 92% of larvae able to survive temperature of -25C for 24 hours. Because of lack of hosts, western United States and Mexico are not considered at risk of infestation.

Hosts

Asian Longhorned Beetke can attack over 100 different species of trees in the wild, but ten to prefer trees in the Acer, Populus, Salix and Ulmus genera. In the United States, maple trees are the preferred host.

Tree genera (families) that serve as larval hosts for Asian longhorned beetle

Genera	Common name
Acer (Sapindaceae)	Maple
Aesculus (Sapindaceae)	Buckeye and horse chestnut
Albizia (Fabaceae)	Silk tree
Betula (Betulaceae)	Birch
Carpinus (Betulaceae)	Hornbeam
Carya (Juglandaceae)a	Hickory
Cercidiphyllum (Cercidiphyllaceae)	Katsura
Crataegus (Rosaceae)	Hawthorn
Elaeagnus (Elaeagnaceae)	Silverberry
Fagus (Fagaceae)	Beech
Firmiana (Sterculiaceae)	Parasol tree
Fraxinus (Oleaceae)	Ash
Koelreuteria (Sapindaceae)	Golden-rain tree
Malus (Rosaceae)	Apple tree
Platanus (Platanaceae)	Planes, sycamore
Populusb (Salicaceae)	Poplar, aspen, cottonwood
Prunus (Rosaceae)	Stone fruit tree
Salix (Salicaceae)	Willow
Sorbus (Rosaceae)	Mountain-ash
Tilia (Malvaceae)	Linden, basswood
Ulmus (Ulmaceae)	Elm
Xanthoceras (Sapindaceae)	Yellowhorn

Scouting for Asian Longhorned Beetles

Ovipostion pits, exit holes, sap or twigs stripped of bark are signs of Asian Longhorned Beetle infestation. Larvae can be difficult to detect because the live and feed inside the tree. Inspecting trees from the ground for signs of damage is the most common method of scouting for Asian Longhorned Beetles. Climbing trees or using hydraulic lifts can improve effectiveness, but is costly and time consuming when surveying large amounts of trees.

There are also traps that use a pheromone lure to detect Asian Longhorned Beetles. Host plant kairomones, along with the pheromone, can greatly increase the effectiveness of traps.

Learn more about traps for Asian Longhorned Beetles

Researchers have also tried acoustic detection for Asian Longhorned Beetles. When Asian Longhorned Beetle larvae feed inside a tree, they produce a distinctive sound that can be detected by sensors attached to the tree.

Dogs have also been successfully trained to detect Asian Longhorned Beetles in the United States and Europe. They are able to smell odors from the frass on tree trunks, or roots.

Asian Longhorned Beetle Management

Eradication

Removing and burning hosts trees has been the only proven, effective, method to eradicating Asian Longhorned Beetle infestations. This has to be done early after infestation to be sucessful though, and it is not always a popular option with the public.

Public efforts have been made to emphasize preventing the spread of Asian Longhorned Beetle through minimizing potential pathways for introduction and developing early detection methods.

Cultural Control

In some parts of Asia, “trap” trees are used to protect other trees from Asian Longhornerd Beetle.  Elaeagnus angustifolia L. and Acer mono are planted within Populus plantations to attract the Beetles. These trees are then removed and burned. Becuase the Populus trees are not preferred, they typically remain safe from infestation. However, when trap trees are not fully removed from a population, they can increase Asian Longhorned Beetle populations after the first year. Tilia mongolica is another popular trap tree that can attract adults from 10m away.

Host Resistance

Efforts have been made in plant breeding to develop cultivars of trees that are resistant to Asian Longhorneed Beetles and other borers.Populus deltoides ‘Lux (I-69/55)’ is one such cultivar that has higher water content in its sapwood which can kill eggs or inhibit development. Interplanting susceptible and resistant cultivars can greatly reduce the risk of Asian Longhorned Beetle infestation.

Biological Control

Biological controls such as natural predators and parasitoids, or entomopathogens are typically safer for the environment than chemical control methods and hav ebeen used in China. However, for the United States and Europe, where eradication of Asian Longhorned Beetles is sought, biological control is not seen as a desirable option. Many of the natural enemies of Asian Longhorned Beetles in Asia, could negatively affect population of other non-invasive wood boring species in Europe or the United States.

Some entomopathogens have had success against Asian Longhorned Beetles. Beauveria brongniartii has shown to increase mortality, however, researches have into found a North American or European isolate, so there is hesitation to use it outside of Asia. Metarhizium anisopliae has also been tested, but with less promising results. Fungal entomopathogens are also difficult to implement, as they often can not withstand extreme temperatures or other environmental factors.

Entomopathogenic nematodes have shown to have some promise in reducing Asian Longhorned Beetle Populations, however they are not currently a viable option, because methods have not been found to apply them to a tree in a manner in which they can find larvae inside.

In Asia there are many predators and parasitoids of Asian Longhorned Beetles. Dastarcus helophoroides is a parasitoid with a broad host range of cerambycids that has been used in Asia, but because the host range is so large, it is not a good option for introduction to other locations.

Sclereodermus guani is another parasitoid that is highly effective against Asian Longhorned Beetles in Asia, however, it is known to attack honeybees, so it is not considered a viable option.

Some native European hymenopteran parasitoids have been found to feed on Asian Longhorned Beetles, even though they are invasive. Studies are currently underway to assess the viability of these parasitoids for wider rearing and release.

Chemical Control

There are several chemical control options for Asian Longhorned Beetles. Cypermethrin is used frequently in China to kill Asian Longhorned Beetles. Clothianidin, dinotefuran, and thiamethoxam have also been used, as well as neonicotinoids, azadirachtin and imidacloprid. Imidacloprid, when injected into trees, can produce an anti-feeding response in larvae. These insecticides do not always translocate evenly within a tree, and can sometimes have negative effects on other insects. Given this, and the relatively high cost of broadly using insecticides, have made this option undesirable for large scale management.

Early detection and destroying trees remains the most effective strategy for eradication. Further studies are needed for biological and chemical controls, before widespread implementation in United States or Europe.