- Wet wood or slime flux is a bacterial disease that causes seepage from the bark of large limbs or the main trunk of oaks and other shade trees. Infected wood is discolored and watery-looking, and the oozing sap has a foul odor that's caused by microorganisms growing in the sap. Slime flux is more prevalent in trees stressed by heat or drought. If the fluxing persists for a long time, the foliage on affected limbs may wilt or yellow.
- No treatments for slime flux exist, as of the date of publication. Inserting a drain pipe into trees to keep the sap off the tree bark was once commonly used, but that practice is no longer recommended. Slime flux usually clears up on its own with no real damage to the tree. However, if dead or loose bark is present where the sap is oozing, remove the bark and let the area dry. Don't apply a wound dressing because such products inhibit the tree's natural healing ability.
- Ramorum blight, also called sudden oak death, is caused by a fungus-like organism called Phytophthora ramorum. This disease first affected plants in Europe in 1993 and was discovered in California in 1995, where it has destroyed thousands of oak trees. The disease also affects other plants, including rhododendrons and viburnums. Infected plants develop cracks in the bark and cankers on their trunks and stems that ooze dark red or black sap. Unlike slime flux, the oozing sap has no foul odor. Infected trees may also develop leaf spots and twig dieback. In the United States, ramorum blight is most prevalent in cool, moist climates, such as northern California. If you suspect your tree has developed ramorum blight, have a tree expert examine the tree. Badly infected trees might require removal, a task best left to experts.
- The best protection against disease is keeping your oaks healthy and free from injury. Most kinds of oak trees grow best in full sun or light shade in moist, acidic soil, although water and pH requirements vary among species. Inspect your trees occasionally for signs of disease, such as leaf spots or galls, and water them well during drought periods. Most importantly, grow a ground cover or mulch around the base of the trees so you don't injure the bark with your lawn mower or weed whacker. Keep the mulch or ground cover 1 to 2 inches away from the bark. Bark injuries create an easy entrance point for fungal and bacterial infections.
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