|Within 14 days, 1 of the 5 tallow trees in my yard has completely succumbed to a fungus. It began by some of its leaves turning yellow and dropping, followed by wilting leaves. The leaves then dried up and turned brown
but stayed on the branches. Now there appears to be a soot type powder on the leaves and the tallow tree next to it is beginning to drop yellow leaves. But since I have a thriving garden and yard with this one exception I have no idea what to do.
|Tallow trees (Sapium sebiferum) are somewhat short lived (about 20 years). If your trees are much younger, the cause will likely be found in the root system. Such sudden death is a sign of a major collapse of the plumbing system of the tree. The tallow has few insect or disease problems. Nevertheless, something has shut down the root system.
I would suspect cotton root rot, but other root diseases are possible. There is no treatment or cure for most of these organisms. Unfortunately you are left to "wait and see". You can watch the base of the tree for mushroom growth or a white mat of fungal fibers under the bark indicating a root rot organism.
Another possibility, although a bit unusual, would be a gas leak underground or damage from a herbicide.