One of the most chattered about insects of the last decade has been the Asian longhorned beetle (Anoplophora glabripennis). The Asian longhorned beetle (ALB) is a wood-boring beetle native to China, Japan, Korea and the Isle of Hainan. Most entomologists and forestry professionals believe ALB entered the U.S. in the New York area around 1996. ALBs are hardwood borers, and due to their aggressive feeding habits, they pose a high level of threat to an array of desirable trees. ALB infestations are often compared to chestnut blight, Dutch elm disease, pine wilt disease and mountain pine beetle in the scope of their potential damage.
Geographic distribution in the U.S.
In August 2013, Asian longhorned beetles had been confirmed in many northeastern states including New Hampshire, Vermont, Rhode Island, Connecticut, Massachusetts, New York, Pennsylvania and Delaware. Infestations have also been detected in West Virginia, Ohio, Michigan, Tennessee, South Carolina, Mississippi, Oklahoma, Indiana, Iowa, Minnesota, Idaho and Washington.*
Asian longhorned beetles are large beetles, with adults measuring .75 to 1.5 inches in length. They have black, shiny bodies with irregular white spots and long black and white striped antennae that are up to two times the length of their bodies. Depending on the weather, adults can be present from late spring to early fall. Both males and females have up to 20 irregularly placed, distinctive white spots on their black wing covers. Their legs are bluish-white in color. Because of their size and weight, flight activity is somewhat limited, although they have the capacity to fly short distances.
A wide range of host trees, both stressed and healthy alike, are susceptible to infestation from ALBs. Hosts include sycamore, plane tree, maple, horse chestnut, birch, Rose of Sharon, poplar, willow, elm, locust, mulberry, chinaberry, apple, cherry, pear and citrus trees. This list is not exhaustive, and it is not unusual when other hardwood species are the target of attack. Nursery stock, felled logs, green lumber, campground firewood, cut stumps, exposed roots, hanging and stacked branches and piled debris are subject to infestation.
Several other beetle species can be mistaken for ALBs. The white-spotted pine sawyer is found throughout much of the East Coast, from southern Canada to the Carolinas and along the U.S./Canada border. Male white-spotted pine sawyers are shiny to metallic black with one white dot at the base of the wing covers. Females are brown to tan with a speckled appearance, but also possessing a white dot at the base of the wing covers. The difference between the two is that ALBs do not have this single white dot, instead they have many white spots on their wing covers. Also, while ALB is primarily a hardwood feeder, white-spotted sawyers typically attack conifers. However, they are also large in size and are present throughout much of the summer.
Another look-alike sawyer beetle is the fir sawyer. It is usually located on the West Coast, a counterpart of the white-spotted pine sawyer. It too is a conifer feeder, infesting Douglas fir, the true firs, and pine trees of many species. White-spotted pine sawyers are also relatively large beetles, with adults ranging from .75 to 1.25 inches in length. They have a similar life cycle to ALBs, with adults emerging in late spring and remaining active throughout most of the summer.
As with the white-spotted pine sawyer, fir sawyers have a white dot present at the base of their wing covers in contrast to the many white spots on the wing covers of ALBs. Further, fir sawyer beetles have a rough and dull appearance, while ALBs appear smooth and shiny.
In the Midwest to the middle south, ALBs can be confused with cottonwood borer. Cottonwood borers are widely distributed from the eastern U.S., north to New York and west to New Mexico. Larvae and adults feed on willow and poplar trees, with Eastern cottonwood being their preferred host. Adults are black and white checkered with black antennae. They are 1 to 1.5 inches in length, making them one of the largest longhorned beetles in the U.S. Adults emerge from late spring to midsummer, depending on the weather, and live for about a month.
Cottonwood borers can be distinguished from ALBs by their solid black antennae; ALB antennae have white bands. Further, cottonwood borers have white strips behind the head, whereas this area of the ALB is black.
In midsummer, females lay eggs into oval grooves they have chewed into the bark. They lay 30 to 70 eggs that hatch in 10 to 15 days. Upon hatching, larvae bore into the tree and begin feeding on the cambium and sapwood, which creates hollowed out galleries beneath the bark layer. Because the larvae are feeding on the vascular tissues, the tree cannot properly transport nutrients and water.
After reaching the adult stage, additional injury results when beetles bore out through the bark creating 3/8-inch or larger-diameter exit holes. Tree sap can often be seen oozing from these exit holes, with coarse sawdust, or frass, evident on the ground or lower branches. Adults usually stay on the host tree from which they emerged, but may disperse short distances to a new host.
Damage and diagnosis
ALB infestations can be very destructive. An infested tree usually dies from borer feeding and vascular system collapse within a year or two. When diagnosing a tree suspected to be affected by ALB, it’s helpful to keep these telltale symptoms in mind:
- Sawdust on the tops of lower branches and around the base of the tree
- Dime-sized holes in the bark that may ooze sap
- Dieback of the upper crown
- Unseasonable yellowing of leaves
Of course, dieback of the upper crown and yellowing of leaves can be symptoms of other maladies, such as disease, drought or soil compaction, so thorough inspection is necessary when dealing with ALB infestations.
Unfortunately, the only effective method of ALB control is to remove and destroy the infested trees. If you suspect the presence of Asian longhorned beetles, contact your local forestry officials immediately so they can take the necessary steps to contain the infestation.
* Source: National Agricultural Pest Information System (NAPIS). Purdue University. “Survey Status of Asian Longhorned Beetle – Anoplophora glabripennis (2010 to present).” Published: 08/20/2013. http://pest.ceris.purdue.edu/map.php?code=INALQCA&year=3year Accessed: 08/25/2013.