In my job as a professional tree fanatic, I have recently
attended two educational sessions on alien tree beetles, the Asian Longhorned
beetle (left) and the Emerald Ash borer (right.) A brief report herewith:
Both of these insects are believed to have arrived in the U.S. via infested packing materials in shipments
from Asia. Their expansion in the Northeast
can be traced back to major shipping ports of entry, although the nearest
outbreak of the Asian Longhorned beetle, in Worcester, MA,
is an anomaly. The Asian Longhorned beetle has not yet been found
in Connecticut,
but the Emerald Ash borer turned up in Prospect in July.
Both beetles have caused large areas of the country to be
under quarantine by the USDA and its Animal and Plant Health Inspection Service
(APHIS). These quarantines restrict the transport of nursery stock, firewood,
logs, mulch or wood chips both in and out of the controlled areas. Currently in
Connecticut, only New Haven County
is under quarantine, but scientists at the Agricultural Experiment Station are convinced
that at least the Emerald Ash borer will be widespread in the state very soon.
Though these are just two of the 350,000 beetles known to
science,both have been exceptionally destructive. In Michigan alone, over seven million ash trees
have been destroyed by the EAB. The ALB, a more omnivorous beetle, known to
destroy thirteen genera, including maple, ash, horse chestnut, elm, mountain
ash, birch, poplar, willow, sycamore, cherry, elm, katsura and hardy mimosa, is
responsible for millions more tree deaths.
While the USDA’s response to the ALB has been to clear-cut
both infested and target trees of the ALB, the plan for EAB is to try to create
equilibrium by slowing the beetles’ spread and by treating the target trees.
So far, the Asian Longhorned beetle has been eliminated in
several regions, including New York City, New Jersey and Chicago,
by means of tree cutting. Early detection is thought to be the best defense.
Both beetles can kill a tree in three to five years. While
the ALB bores deep into its host tree, the EAB larva lives and feeds just under
the tree’s bark, creating wavy lines where it has fed on the growing portion of
the tree, known as the cambium. Ash trees locally often exhibit signs of Ash
decline, an umbrella term that covers response to air pollution, drought,
various fungi, and a mycoplasm-like organism that infests many ash trees.
This pervasive decline will make discovery of the EAB
problematic, since so many ash trees already look, as Dr. Kirby Stafford of the
Experiment Station said recently, “crappy.”
So what’s to be done? For local residents who value their
trees, including those poor, benighted trees growing along the right of way,
careful inspection is the best defense. The ALB chews its way out of its host
tree, leaving a round exit hole a quarter inch or more in diameter (see above). The EAB,
being much smaller, burrows out through a distinctive D-shaped hole, about an
eight of an inch wide (below).
Trees infested with ALB often have piles of sawdust or frass
at their base. Many trees will show a significant amount of dieback in their
upper canopy. Hotlines have been established for both beetles, but it is a good
idea to check the internet to verify what you think you are seeing.
For EAB, the best website is: www.ct.gov/deep/eab
and the hotline number is: (203) 974-8474.
Much has already been learned from other states’ experience
with these two beetles. Surprisingly, the biggest factor in preventing the
spread of the two beetles is not moving firewood away from the site where it
was cut. This is the major reason for the quarantine, since these insects can
live in cut wood for up to a year.
So, if you are buying firewood, make sure you know where it
was cut, and avoid wood from New Haven
County or anywhere outside of Connecticut.
