There are many hemlock trees around the lake. If you noticed that several branches are loosing their needles and, in general,the hemlock tree looks unhealthy they may infected. Around the lake the two most common and deadly pests are the Woolly Adelgid and Elongated Henmlock Scale. The Woolly Adelgid looks like little white woolly attachments on the needles. The Elongated Hemlock Scale can be observed on the lower needle surface and is extremely small. They are light yellow brown to brownish orange. Below are two links that describe the pests in greater detail and what you can do to control them. Here are links to some futher information. Prevention and treatment includes spaying the trees with an oil.