The Arnold Arboretum’s famed Hemlock Hill has been severely impacted by the adelgid, and more than 100 trees have been lost. (They opted against an attempt to introduce ladybugs, as was done at Hemlock Gorge.) The Arboretum staff are undertaking an extensive research program that is described in some detail at their web site: https://arboretum.harvard.edu/plants/hemlock-hill-history-management-and-research/