Decidua

Decidua is a disease that effects @Dryads , Bark Druids , and Half-Dryads . It derives it's name from the natural term deciduous. Deciduous is used to reference the natural process of when plants shed leaves or limbs as part of a hibernation process. Normally the sentient plant folk tend to not be affected by this otherwise natural process.
Decidua was discovered several thousands of years ago when a few dryads began spontaneously loosing limbs. Not just limbs on their home trees but limbs on their bodies instead. There were tales of dryads arms falling to the moss covered ground mid conversation with other species. The stumps left jagged and dry. Decidua started to spread to other tree kind such as the male equivalent of the drayds, the bark druids. The half-drayd also suffered.
The diseases' first symptoms consist of a extremity pain. Loss of leaves is also an early on set sign. Dark barked tree kind will sometimes begin to loose color and lighten on the extremity that will be lost. Lighter bark kind, like the birch for example, do not get the grace of the extra warning.
A few fey have witnessed a lost limb in person and describe it as peculiar followed by terror. The tree kind will often experience pain and symptoms before the loss but there is no other warning as to what limb will fall where or when. There has been only one report of a tree kind loosing their head as an extremity. It has not been made certain if this was due to a logging mishap or a result of the disease.
It was a Pixie by the name of @Hood who found the remedy. His clan of pixies lived in the boughs of a grand dryad tree and small branches had began to fall leaving their dryad finger-less. Fearing their matron harmed and their home destroyed the pixies began searching for a cure. Unfortunately they were not able to find one before their dryad patron suffered further losses at the horror of a disease.
The cure was found within the Thundering Basin's lake. A specialty kelp grows there, and only there. By mixing it with other curative academical ingredients Hood was able to create a potion that can dissipate Decidua when the signs first arrive. The potion cannot grow back the missing limbs but does prevent anymore loss. It is not uncommon still to see a member of the tree kind missing an arm, a leg, a few fingers, or more as the disease has become recently treatable.
Further studies continue to find a cure, similar to the mortals vaccines.