Beetles Released for Hemlock Health

It was a perfect May evening in Newtown, blue skies and warm temperatures. A number of friends and members of Protect Our Pollinators had gathered just beyond the Newtown dog park where a line of hemlocks displayed the white, woolly-looking clusters, evidence that these trees had been infected with Hemlock Woolly Adelgid (HWA). Left unchecked HWA can destroy enough hemlock needles to put the tree in serious condition in just a few years.

So, it was beetles to the rescue as two containers of St (Sasajiscymnus tsugae) beetles were about to be released into the tree branches. These beetles are native to Japan where they act as predators and keep the adelgids under control. However, St beetles are not native in the U.S. and are raised here by one grower in Pennsylvania (Tree-Savers) who is the supplier of St beetles to sites in the eastern U.S. states.

These tiny beetles are shipped in round plastic containers which contain up to 100 beetles, a damp wafer-like sponge, and some excelsior material, all of which were kept in a cool place where the beetles had become quite inactive. But once they were exposed to the warmth of a sunny day, they showed that they were ready to call Newtown their new hometown – and that they were ready for a meal.

Third-grader Josie Rivera holding beetles.

Third-grader Josie Rivera, a lover of science and especially insects, was more than happy to help with the release. As a container of beetles was handed to her, she intently focused on her “charges” as she helped to attach the contents of the plastic container to the tree. Once done, she was all smiles, knowing that she had helped the beetles and the trees.

The release of St beetles has been done by the Connecticut Agriculture Experiment Station since the early 1990’s. Success of this program is evident by healthy hemlocks in hundreds of acres of state forest and park lands that have been saved through the release of this beetle. 

The St beetles feed only on adelgids, making them a perfect bio-control method in that they do not impact non-target species. Luckily, they survive Connecticut winters, making them a sustainable control measure since new beetles do not have to be released the following spring. They are smart enough to leave some adelgids to allow for food for future generations, but eat enough adelgids to provide for health of the hemlocks. 

Protect Our Pollinators was proud to initiate this project, with the approval of Newtown Land Use and the help of Dan Holmes who identified the site and made it accessible for the event.

Written by Mary Gaudet-Wilson