In 2013, the Hemlock Woolly Adelgid was discovered by Park Naturalist, Dale Luthringer in Cook Forest State Park. HWA is an invasive species that was accidentally brought to the United States from East Asia in the 1960’s. It feeds by sucking sap from Hemlock trees. If the Hemlock trees are left untreated, HWA can kill a Hemlock tree in as little as 5 years or more depending upon the tree’s size and vitality. Treatment for the Hemlock Woolly Adelgid involves several measures
Imidacloprid is an insecticide that is administered near the base of the tree. The insecticide moves up through the base to the trunk of the tree to the feeding sites. The insecticide is not a one time treatment plan, and does need to be reapplied approximately every 5 years.
A predatory beetle from the Pacific Northwest is also being released on to Hemlock trees. The beetles’ eggs are left on HWA larvae and when the eggs hatch, the beetles feed off of the Hemlock Woolly Adelgid. The beetles initially disperse up the tree and then away from it 40 meters per year.
In addition to these treatment measures, Mother nature assists the Hemlocks by providing long durations of extreme cold temperatures that naturally kill off the infestation. Unfortunately, with increasing warmer temperatures due to climate change, these cold spells are becoming less frequent.
