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HWA and EHS?

Many of us are aware of Hemlock Woolly Adelgid (HWA), but have you ever heard of Elongate Hemlock Scale (EHS)?


EHS is an insect that can spread to hemlock trees. It forms brown scales in an elongated oval shape on the main body of the hemlock needle. Similar to HWA, EHS steals the hemlock needles’ nutrients. This in turn causes the needles to turn yellow and eventually fall off. In a heavy infestation, the hemlock tree can die from being defoliated.

Unlike HWA, EHS can spread to other tree species than just hemlock, including species like fir, spruce, and other economically and culturally important tree species dominant in the upper peninsula. EHS can also spread by birds and wind, so it can very easily spread throughout an entire stand.


Elongate Hemlock Scale

Hemlock Woolly Adelgid

While EHS has not been on the radar of many forest managers within the U.P., annually rising temperatures in the winter months is causing a growing concern that EHS and HWA alike will have a greater opportunity at getting into our forests and then establishing themselves. This is thought to be because HWA is said to die if it is exposed to temperature less than zero degrees Fahrenheit. If either spreads to the U.P., massive damage to our forests both economically and ecologically could occur as these are fairly fast spreading invasives with limited, accurate control methods.

So, the next time you find yourself in a stand of hemlock trees, take a look around and see if your notice EHS or HWA as early detection is our best bet at combating both of these invasive plant species.

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