By Stacy Kish
The Asian longhorned beetle, Anoplophora glabripennis, is a wood-boring insect that is capable of destroying 30% of the urban trees in the United States at an economic loss of $669 billion. Infestations of this invasive beetle have been found in Ohio, New York, New Jersey, Massachusetts, and Illinois, and they have been shown to feed on more than 100 different tree species, with a preference for maples, poplars, aspens, cottonwoods, and willows.
Now a new, open-access article in the Journal of Integrated Pest Management (JIPM) provides a comprehensive overview of the ALB, including a review of its biology, life stages, distribution, ecology, and methods of detecting and controlling it.
“There have been several reviews of ALB that were more for scientists, but this one is more for managers — people who are dealing with them,” said co-author Melody Keena, a research entomologist with the U.S. Forest Service. “This is a good summary of the scientific backing for everything the cooperative eradication programs are doing. They can point the public to this document for more information, especially because it’s written for JIPM in language that non-scientists can understand.”
As its name implies, the invasive ALB is originally from Asia. Adults are quite large, measuring up to 39 millimeters in length, and their long antennae can be as much as twice the length of their bodies.
“These are big beetles,” Dr. Keena said. “Some of the larvae can be the size of a woman’s little finger. They can be substantial, and a single ALB larva can consume 1,000 cubic centimeters of wood.”
The supplementary tables in the JIPM article will be particularly helpful for managers, according to the authors. The first lists nearly 160 different trees on which the ALB can feed, oviposit, or complete development under field conditions. Another lists tree species that are not considered to be ALB hosts, so they may be good choices for replanting efforts.
Because of their size, one might think that detecting the ALB would be easy. However, they tend to stay quite high in the trees, which means that teams of trained surveyors or tree climbers are required to look for the telltale signs of an infestation, which include boreholes, exit holes, frass, and sap oozing from tree wounds. Other means of detection include sniffer dogs and pheromone traps.
When detected, the most effective means to eradicate the beetle from an area is to burn or chip the infected trees and grind the stumps. However, this approach is costly and may be controversial with the public.
One possible control method that may be promising in the future involves spraying an entomopathogenic fungus (a fungus that kills insects) on tree trunks and branches, along with trail pheromones that would be used to lure them to the trees.
“It’s the old idea of attract and kill,” Dr. Keena said, “but it’s got a little ways to go” as scientists at Cornell University work out different spray formulations and how to use the pheromone with it.
The eradication programs and other control methods take advantage of the ALB’s tendency to stay in a tree for long periods of time.
“They don’t love to fly and will often stay with one tree as long as it’s viable,” Dr. Keena said. “So they don’t spread as much as other insects, like the emerald ash borer.”
In China, they have taken advantage of this by using some trees as “traps” in a forest to attract the beetles. Then after infestation, they are cut down and burned before the adults emerge.
In its natural habitat, the beetle is kept in place by host tolerance of native trees and by natural enemies. However, the idea of introducing another species into a non-native habitat is perhaps even riskier than the initial unintentional introduction of the beetle, so scientists are looking for parasites of native wood-boring beetles to determine their efficacy on the ALB. The jury, however, is still out on this approach.
Most commonly, the public is the first to notice, investigate, and alert officials about infestations. This is important because the sooner these beetles are detected, the better.
“We highlighted early detection as an important part of the eradication program because the faster they are found, the less they have spread,” Dr. Keena said. “Traps baited with pheromones and plant volatiles (plant smells) that our research group developed are a newer tool that is helping to detect this beetle, but all infestations found in the U.S. to date have been spotted by the public and brought to the managers’ attention.”
The authors hope that forest managers and others will put this insect profile to use.
As Dr. Keena said in an interview, “When JIPM’s Co-Editor-in-Chief Marlin Rice invited me to write this article, I invited Peter Meng, a Pennsylvania State University graduate student to take the lead, because JIPM articles allow graduate students to take a lot of their literature searches results and thesis introductory material and put it into a format that’s actually used by somebody.”
The failure to control the spread of the ALB could be disastrous for native forests and urban trees in the U.S. If you suspect the ALB to be in your area, contact your local forestry office for assistance.
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