Invasive Species of the Week: Asian Long-Horned Beetle

I feel obligated to begin my series of spotlights on individual invasive species with the one I am currently working with - the Asian Long-Horned Beetle.

Seen here, the ALB is generally an inch to an inch and a half long with a black body and white spots. The feet and legs of the adult beetle tend to be blue-ish. Their antennae can be quite long - as much as four inches.

Originally from Asia (where it is known as the Starry Sky Beetle), ALB came to the United States in the late '90s in wood-packing material. Since it left Asia, it has also been found in Canada and parts of Europe (Austria, France, Germany, Italy). In the United States, it was first discovered in Brooklyn. It has also been found in New Jersey, Chicago, and two different parts of Massachusetts.

Here you can really see the blue feet.

ALB is an invasive species that is uniquely threatening to the trees it reproduces in. Its reproductive cycle is quite harmful to even healthy trees. The female chews a spot on a tree for each egg she lays - 30 to 90 for each mating. The eggs hatch within a few days and as the larvae develop they chew their way through the tree into its heartwood. This means that the beetle is disrupting the phloem and cambium layers of the tree, essential for transporting water and essential nutrients from the roots up to the canopy and out to the branches. The larvae develop into pupae within the heartwood of the tree and finally hatch into adult beetle sometime during the winter months. The adult then chews its way back out to the surface, destroying more of the tree as it goes. They emerge anywhere between April and October and leave perfectly round exit holes roughly the size of a dime.

Here we see a perfectly round exit hole (they lie flush with the tree's bark on all sides much like a bullet hole would) and a few rust-colored oviposition sites where the female chews the bark to lay an egg.

ALB's favorite host trees include Acer (Sapindaceae), Populus (Salicaceae), Salix (Salicaceae), and Ulmus (Ulmaceae) - otherwise known as Maples, Poplars, Willows, and Elms, some of the most populous trees in the eastern United States' hardwood forests. Without a natural predator, ALB manages to spread with relative ease in this country, despite the fact that it cannot fly long distances on its own due to its size. Larvae and pupae have been transported in firewood and cut timber. Adult beetles can cling to traveling cars. Once infested in a host tree anywhere near other hosts, the beetle can easily spread through an entire stand - or a forest.

Luckily for us, most of the current infestations of ALB have been in urban landscapes where it is relatively easy to find, treat, and eradicate the beetle before it can spread much farther (Brooklyn, Chicago, Jamaica Plain). However, there are two important cases where this beetle can and could have gotten away from us to infest entire forests. The first case where this might have happened was in Toronto. Here, the government recognized how important it was to contain the spread of ALB and they ordered a complete removal of host trees in the affected area. It worked; ALB is no longer in the area (although they continue a vigilant survey to maintain this status).

The second case is right here in my current hometown - Worcester, Massachusetts. An infestation of ALB was discovered here in 2008 - with some evidence indicating that the beetle may have been here since as long ago as 1997. Since that time, five towns in the area have been declared infected (Worcester, Boylston, West Boylston, Holden, and Shrewsbury), and more than 30,000 host trees have been removed. There is a quarantine in the area denying individuals transport of host material out of the quarantine zone unless it has first been inspected by the USDA. There is also an ongoing eradication effort being conducted by the USDA. I am a part of this effort, being one of the ground surveyors working for a contractor to the USDA in the area. I have heard numerous estimates about the potential damage the beetle could cause if it gets away from us here in Worcester - the most horrifying being the billions of dollars of economic damage if they infest and ultimately damage the majority of our maple-dominated forests. (Imagine the effects of no more maple syrup or anything else associated with those trees.)

There are currently 12 host species in this area: Maple, Poplar, Elm, Willow, Ash, Mountain Ash, Birch, Hackberry, Sycamore, Horsechestnut/Ohio Buckeye, Katsura, and Mimosa. In Canada, Rose-of-Sharon was also listed. There are also several other species that are questionable hosts (beetles may have infested them in a lab situation - or laid eggs in them that never hatched). For our part, we are conducting a thorough ground survey of all the host trees within the quarantine zone. Any suspicious tree are climbed by USDA climbers. All positive trees are cut, chipped, and their stumps ground to eight or so inches below the surface.

A replanting effort is in place with the goal to replace every host tree being cut. Replacement trees include: Serviceberry or Shadbush, Ironwood, Southern catalpa, Turkish filbert, Ginkgo, Honey locust, Kentucky coffeetree, Tuliptree, Dawn redwood, White oak, Swamp white oak, Bur oak, English oak, Japanese lilac, Bald cypress, Basswood, and Little-leaf Linden.

* USDA site about their ALB eradication program (APHIS)
* Mass.gov's information site
* An excellent identification site with many common look-alikes
* Washington Post article providing a brief overview of invasive insects in the US and the damage they could cause