The chestnut blight fungus usually cannot attack the roots of chestnut trees, because other microorganisms in the soil attack the blight fungus. One can take advantage of this phenomenon and cure individual blight cankers by moving soil up onto the trunk of chestnut trees. You do this by placing a soil compress (or mud pack) over the canker.

The blight fungus attacks chestnut trees by forming cankers on their stem. A canker is a region of dead bark on a tree. Chestnut trees are killed by blight when a canker completely encircles the stem, cutting off the flow of water up from the roots to the leaves and the flow of sugar down from the leaves to the roots. Trees can have multiple cankers, and each one is capable of encircling the stem. To protect trees from blight using soil compresses, it is necessary to treat each canker on the tree. Furthermore, continued vigilance is necessary to detect and treat new cankers on the tree. In general, soil compresses offer a means of prolonging the life of chestnut trees; they are not a general cure for the disease. As trees increase in size, it becomes increasingly difficult to treat all the cankers on the tree, especially higher in the tree, and it also becomes more difficult to detect cankers that need to be treated.

For a soil compress to work, the soil must be held in place over the entire canker and kept moist. You can do this by covering the compress with shrink wrap, sold at building supply stores. The 4" rolls are easiest to handle.

The other important requirement is to have the compress extend at least 1 foot beyond the top and bottom edges of the canker, so that the canker doesn't expand beyond the edge of the compress before the soil microorganisms have a chance to attack the blight fungus.

The easiest way to apply a compress is to make gooey mud from soil around 10 feet from the tree and stick it to the cankered area, completely encircling the stem. Sometimes you can stick the mud to the tree by forcefully throwing handfuls at the stem. Be sure to completely cover the stem. Then wrap the mud firmly with the shrink wrap and completely seal.

Every month, check the top and bottom edges of the compress to make sure the canker has not expanded beyond the edges. Remove and reapply the compress after 1 year.