A biocontrol, a black beetle named Laricobius nigrinus being released in US studies is proving
Hemlock woolly adelgid (HWA) is spread by nursery stock, migratory birds, and deer
successful in controlling the winter stage of the hemlock woolly adelgid, HWA. However, as the pest is active and reproducing in spring, it continues to expand in the test areas.
Taylor Scarr of NR Canada said, “The next generation recovers and takes over.” As a result scientists from both the US and Canada are working together to collect other potential biocontrol agents for testing. The “new” insects are actually native to British Columbia, silverflies.
Scarr continued, “We are working with US researchers to look for biocontrol agents, go through the screening process and determine how to produce them in high enough numbers for release.”
Although the insects are native to Canada, the process for release is just as rigorous as if the insect was from overseas due to the change in ecosystems.
Sources of spread of HWA include nursery stock, migratory birds and deer. Natural winter decorations containing hemlock are also suspect and subject to quarantine regulations.
An arborist and a landowner are congratulated for their support after the 2012 discovery of the invasive pest in Etobicoke, Ontario. Scarr said, “An arborist spotted the pest and reported it. Rapid response is always the preferred option. The infestation was from infected nursery stock. It is easy to diagnosis when you know what to look for. The woolly masses along the twigs are HWA.”
Ontario’s second HWA find was in 2013 in the Niagara gorge. The cause was migratory birds. Nova Scotia continues to have a major infestation as the insect is thriving in their maritime climate.
— Pat Kerr