Public Comment Period Open Until Feb. 23, 2018

  • Hemlock Woolly

by Piera Siegert, State Entomologist, NH Dept. Agriculture, Markets & Food

The hemlock woolly adelgid (HWA) quarantine – a joint quarantine by the Dept. of Agriculture, Markets & Food and the Dept. of Natural and Cultural Resources – is currently under review. The benefit of the HWA quarantine has been reduced over time as HWA populations have become established across the state, with natural dispersal of the insect outweighing the contribution from the human-assisted movement of potentially infested nursery stock and wood products.

A small insect from Asia capable of killing hemlocks, HWA can be spread through the movement of infested hemlock material as well as through natural dispersal by wind, birds, and other wildlife. HWA was introduced to the United States in the mid-1950s and is now established from Georgia to Maine. In New Hampshire, a quarantine on hemlock nursery stock and wood products was enacted in 1988 to protect the state’s hemlock resources and reduce the opportunity for introduction of this pest through trade. First found in Portsmouth in 2000, HWA has now been detected in 120 towns across the state and from every county except Coös. The original quarantine was periodically revised as new HWA detections occurred within the state and nationally. While historically the HWA quarantine was successful in reducing the number of new HWA introductions, its value has waned as HWA populations have slowly become established across the state. Today, most new detections of HWA in New Hampshire tend to be correlated with natural movement of the insect rather than trade.

Eliminating the HWA quarantine does not eliminate all state HWA regulations and protections. HWA is a prohibited invasive species and subject to the state’s invasive species rules and penalties related to movement and distribution of this pest (Agr 3802.01). As a dangerous insect, HWA is regulated under the state’s nursery stock rules and detection during a nursery inspection will result in a stop sale order of hemlocks until the risk is addressed through treatment or disposal (Agr 2501.04). To maintain nursery stock as low-risk for transporting HWA, the state recommends following best management practices (BMPs). BMPs for nursery stock would include buying from reputable suppliers, routine inspections of imported hemlocks for HWA and other pests, treatment of hemlocks with signs of infestation, maintenance of customer records, and providing information about maintaining hemlock health to customers. HWA can be treated in landscape trees through use of targeted pesticides.

The Division of Forests and Lands responds to detections of HWA in forested settings. Their program includes annual surveys, cultural controls, pesticide applications, BMP recommendations, and a bio-control program.

A public comment period will be open until close of business, Friday, February 23rd. Comments may be submitted by email (, fax (603-271-3692), or mail (ATTN: Piera Siegert, Div. Plant Industry, 29 Hazen Dr., Concord, NH 03301). More information about HWA, its status in NH, and BMPs are available on, as well as the Division of Plant Industry’s webpage.