QuestionQUESTION: The bark on my live oaks appears to be splitting and falling off. More noticeable when you look at almost all the trunks and branches they are all grooved where a portion on bark had fallen off and the tree had mended itself. The problem appears to have been progressing for quit while.
What disease or parasite could cause this damage and will I be able to reverse the damage or at least stop the progression. The trees are in the neighborhood of 50 to 70 feet high.
ANSWER: Sounds like one of the canker diseases. If you could a picture would really help. Most cankers are not much of a problem but one can be. Hypoxylon canker can over time kill the tree.
The canker is caused by one or more species of fungi in the genus Hypoxylon. Found in the outer bark areas of living and healthy trees, the fungi are normally of little consequence. However, Hypoxylon can severely injure or kill trees weakened by factors such as drought, root disease, mechanical injury, logging or construction activities. These agents of stress enable the fungus to move into the xylem and produce cankers on the branches and trunk. Apparently, the fungus is activated by reduced moisture in the xylem and bark. Once this low moisture threshold is reached, the fungi quickly spread. Especially in drought areas, Hypoxylon fungi are often associated with tree death. Other fungi found in weakened trees may also play a role.
Trees infected with Hypoxylon often develop severe injuries on the branches or trunk. They may also exhibit crown dieback. Large patches of bark of infected trees often slough off along the trunk and major branches revealing the fungus fruiting bodies . In spring or early summer, powdery greenish to brown or gray masses of the spores (conidia) are produced on the surface of crusty, fungal tissue patches (stromata). These stromata are the most obvious signs of Hypoxylon canker. They vary from less than ?inch to 3 feet long or more, running along the stem and main branches. In the summer or fall, these stromata thicken, harden, and turn silver or bluish-gray to brown or to black depending on the Hypoxylon species. Small slightly raised dots may be found on the surface of these masses. These are the tops of small chambers where a second type of spore (ascospore) is produced.
Cankers are usually a sign of the tree is under stress.
There is no known control for Hypoxylon canker once symptoms begin to appear. Because the disease is internal and kills the sapwood of the tree, fungicide sprays are completely ineffective.
Valued trees in home landscapes should receive additional care during drought periods. Watering should begin before injury occurs. Apply one inch of water per week during the summer. Place a pan under the tree and turn the sprinkler on and when the pan has 1 inch of water in it stop. Fertilization at the rate of one pound of 13-13-13 per inch of trunk diameter should improve the vigor of drought stressed trees and make them less susceptible to disease attack. Fertilize now and again in the Fall. The fertilizer should be spread on the soil surface beneath and 20% beyond the drip line of the crown of the tree and watered in good. If you fertilize right before a good rain storm you will not need to water.
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QUESTION: We just purchase the property but yes the house was just build 4 years ago and it may appear to be the stress and drought that is causing the canker. Will try to fertilize and water to save the beautiful trees. thank for your expert advise. Will send pictures.
Will cutting back the crown and any branches help restore the health of the tress?
AnswerCutting the dead limbs will decrease the amount of fungi spores but cutting the live limbs will weaken the tree. The tree will need all the foliage it has to produce food for the root system that in turn will transport water and minerals to the foliage . I would not prune the tree.
