Exotic Pests

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(Host) Commentator Charlie Nardozzi says that we need to be on the lookout this summer for a couple of unwelcome visitors to our trees and shrubs.

(Nardozzi) As many gardeners have noticed, mild spring weather has favored the widespread outbreak of summer shrub and tree pests such as tent caterpillars and viburnum leaf beetles. Although their feeding can cause defoliation and stress to plants, it’s other more exotic tree pests that haven’t breached Vermont’s borders that have agricultural and forestry officials worried.

While nature has developed natural checks and balances for native pests or ones that have been in the environment for years, pests imported from foreign shores usually have few natural predators, so can wreck havoc on our greenery. All a gardener has to do is watch the Japanese beetles feeding on roses to understand the danger an imported pest can bring.

Over the years, Asia has been the source of many varieties of flowers, trees, and shrubs. Unfortunately, they’ve been exporting a few other wild things with the plant material.

The Asian Long Horned beetle was first discovered in Brooklyn, New York in 1996. This one inch long, black with white-spots and a long antennae beetle attacks many hardwood trees. Left unchecked it can kill a tree within 5 years. The concern is that one of its favorite hosts is our beloved maple tree. Quarantines in areas that have experienced long horn beetle outbreaks such as Brooklyn, Chicago, and Jersey City seems to have limited the spread of long horned beetles for now. Still forestry officials warn people not to transport firewood across state lines since the long horn beetle might be hitching a ride.

Another new Asian import is the Emerald Ash borer. It was first discovered in Michigan and Ontario in 2002 and has spread to Ohio and Maryland. In two years it has killed more than 6 million ash trees in Michigan alone. The insect is a metallic green, wood-boring beetle. It favors green, white, and black ash trees. Often the tree is dead within a few years of the initial attack.

Finally a more immediate threat is an exotic pest of hemlock trees that has invaded southern New England states. The hemlock woolly adelgid is a small, sucking insect often found in a cottony white mass on the underside of hemlock needles. Although diminutive in size, it can kill a healthy hemlock tree in a few years. Hemlock is an important lumber tree as well as vital for wildlife habitat, stream bed erosion control, and deer yards. This spring a shipment of hemlocks from out of state was found to have the adelgid insect on them. The state Department of Forests, Parks, and Recreation has been trying to locate the 800 hemlock trees that were sold from that shipment to destroy the insect before it gets released into the wild.

Although officials are doing what they can to control the spread of imported pests, it’s ultimately up to gardeners and homeowners to keep a sharp eye out for damage to their trees and shrubs. If you purchased a hemlock tree this spring from a local nursery, call the Forests, Parks and Recreation Department to have them inspect for the adelgid.

This is Charlie Nardozzi in Shelburne.

Charlie Nardozzi is an all-around gardening expert with a special fondness for tomatoes and roses.

These agencies have more information on the woolly adelgid:
Vermont Agency of Natural Resources
University of Vermont Extension Service
Vermont Department of Agriculture
U.S. Forest Service

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