Laurel wilt is a heart-wood disease introduced (vectored) to the plant host via ambrosia beetles. It's been around for at least the past 15 years, in the eastern US. Any member of the Laurel (Laurales) plant family can be infected. There are treatments to both protect your Sassafras, Kalmia, Lindera, Sweetbay and Bay Laurels.
Infection is visible as distorted/puckering leaves, especially younger. These will brown as seen in the second pic of an infected Sassafras. The browning is due to the vascular tissue being infected and not being able to get water to the leaves from the roots. Illustrated by the increasingly diseased twig pics. The fungus enters the woody tissues via an ambrosia beetle and thus, the fungus can be found just under the bark.
Far too often, people tell me they contact a tree care company and the only solution to a sick tree they are given is removal. We have to think differently!! Trees are critical to our air quality and water quality. They are especially important in our cities and suburbs for these (and other) services they provide us. Housing and all types of development, typically 'mows' them down planting little saplings that will take decades to provide the same air and water quality improvement (not to mention saving on AC bills in the summer months). So, save em if you got em!
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Picture credits for the bark infection peel and the sassafras are:
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