Extension Educator, Horticulture
Every spring we get calls at the Extension office about sick trees. Some trees leaf out fine but quickly the leaves die. So does that mean it's time to play taps?
First, we need to know if the tree is dying or just playing dead. A vital piece of the puzzle is, "What kind of tree is it?" Different tree species have different problems.
Some trees like to play dead. For instance trees such as sycamores and ash can look pretty sad right now. If you look around town you are sure to see a few trees with just a fringe of green leaves on top. The rest of the branches appear dismally naked. Each year sycamores (or is it "sickagain?") get the fungal disease anthracnose to some degree. It is however worse in years when we have cool wet springs. Even though we had a dry period earlier, sycamores are showing anthracnose symptoms.
The fungus can kill the first set of leaves so sycamores appear to leaf out late or have sparse leaf cover. It can also cause stem cankers that result in branch dieback. Sometimes small dead branches will litter the ground under a sycamore. Different forms of the anthracnose fungi can also infect ash, maple and oak.
Anthracnose can be fairly severe in ash trees. Often ashes appear healthy but not as full of leaves or more dramatically it can cause the first set of leaves to drop. However, ash can get a couple of more serious diseases called ash yellows or verticillium wilt so check the branches for life.
To determine if branches have the ability to leaf out again, look for live buds on the twigs. Live buds should appear green and plump. Also try scratching the new growth with your thumbnail. Stems should look green and moist. If the buds and branches are dead, the tree may have a more serious problem.
Keep in mind not all problems with trees are caused by infectious diseases or insects. When new leaves are damaged by cold and high wind, they can appear to be suffering from insect damage. Late frost damage usually appears on the tops of the trees where anthracnose appears in the lower canopy. Several of my trees looked horrible after our cold spell and high winds, but are now showing signs of new leaves. With weather damaged leaves, there is no pattern to the damage and the holes in the leaves are jagged. Leaves with wind damage may also have straight-line rips in the tissue. If leaves are damaged while still in the bud, a uniform pattern may appear as they unfurl. Maples often show a great deal of leaf tatter.
If you are not sure the cause of the problem, samples can be taken to the U of I Plant Clinic, 1401 St. Mary's Road, Urbana 61802 ($12.50 fee) Phone: 217-333-0519, http://plantclinic.cropsci.uiuc.edu/ for proper sampling. Provide stem and leaf samples. For leaf samples - Collect early and late stages of infection. Press leaves between heavy paper or cardboard. Do not put in plastic.
Samples can also be taken to the nearest U of I Extension office. http://www.extension.uiuc.edu/
We don't have tree defibrillators, so our ability to revive a tree is limited. Generally the best management option is to promote good tree health; water during drought periods, remove dead or dying branches and fertilize if necessary in fall. Make sure trees are not planted too deep. Three to four inches of wood chip mulch is helpful but keep mulch away from the tree trunk.
Fungicide sprays are not effective for anthracnose once symptoms appear. Fungicides for the most part prevent infection so they have to be applied before infection occurs. Generally anthracnose is not life threatening and trees will eventually re-leaf.