Quarantine Update: Hemlock Woolly Adelgid

By Allison Kanoti Forest Entomologist, Maine Forest Service

Adapted from an article printed in the February 2010 SWOAM newsletter

It is decidedly winter here in Maine; most life forms have slowed down to take the edge off the challenges of the season. Not so for the hemlock woolly adelgid (HWA). After sleeping through the summer (aestivating), it began feeding around the time the leaf peepers left.

As it feeds, the adelgid adds to its woolly coat. Eventually, the ball of fluffy wax surrounding the insect can exceed 0.25-inch in diameter. At its largest girth, the wax coating is fluffed up by the hundreds of eggs it conceals. Those eggs, and the crawlers that hatch out of them, are the reason Maine has a quarantine.

In the late 1980s, as they watched the devastation caused by HWA in neighboring states, forest health staff in northern New England decided to fight its spread. No federal quarantine existed on the insect, so the states worked together to establish quarantines on live hemlocks and other hemlock products.

In Maine (and in other states with quarantines) there are strict limits on movement of live hemlock from infested areas, and less severe restrictions on movement of other hemlock material. Live hemlock material has a high risk for spreading HWA whatever the season. All stages of adelgid can survive to produce eggs and offspring on live hemlock material. Only one insect is needed to start a new population (all North American HWA are female), and low populations of adelgid are difficult to find.

For other hemlock products, the risk of spreading HWA changes with the season. In March, when eggs are first deposited, the risk is relatively high. It remains high through July when eggs and crawlers, the stages of the insect that can survive without live host material, are abundant. By August, the majority of the crawlers have settled, and the risk of spread on forest products is low. For this reason, landowners within the HWA quarantine are urged to market their hemlock forest products between August and February. During those months, landowners will have the most markets available and the lowest risk of spreading adelgid, both to and from their woodlots.

The change in risk for hemlock cut or held within the quarantine area is addressed in compliance agreements administered by the Maine Forest Service. The agreements and quarantine rules mandate:

• All material harvested within the quarantine area, regardless of type or season must either stay within the quarantine area or go to a facility with an agreement to handle potentially infested hemlock material.
• Chips/hogfuel/other uncomposted material with bark may be moved year round but must be moved in a completely enclosed vehicle.
• Round wood (logs, stumps, etc.): From March through July (high risk period-eggs and crawlers abundant): Hemlock logs and other round wood must be inspected and found apparently free from hemlock woolly adelgid before it can leave the quarantine area. Inspections of the stand prior to harvest are recommended, as the result of the inspection could impact the type of product that can be marketed. From August through February (low risk period-eggs and crawlers less likely to be abundant): Hemlock logs and other roundwood can be moved without inspection.

The Maine Forest Service Forest Health and Monitoring Division maintains compliance agreements and conducts inspections within the state. Canada, New Hampshire and Vermont also quarantine material coming from areas infested by hemlock woolly adelgid.

Most forest land in Maine does not fall within the quarantine area for hemlock woolly adelgid. The adelgid is restricted to southern and coastal York County. The quarantined towns in Maine include Eliot, Kittery, Ogunquit, South Berwick, Wells and York. Much of the hemlock’s range south and west of Maine is also quarantined.

Landowners throughout the southern half of the state (where climate favors HWA survival) should maintain vigilance in monitoring for this pest. Those near and within infested towns should take steps to reduce risk of introducing HWA to their properties or spreading it to neighbors’ land. These include removing bird feeders during the high-risk period (birds are a primary mode for long distance spread of the insect), trimming hemlock foliage likely to come in contact with other potential vectors (vehicles, etc.), and timing harvests to occur during the low-risk period (to reduce risk of spread to and from your woodlot on harvesting equipment).

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