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TREE PROBLEMS...TREE PROBLEMS...OH SO MANY TREE PROBLEMS!
My phone's been ringing off the hook from people with tree problems. Here are some of the biggest problems being reported:
Ash trees leafing out poorly. Most likely, the cause is weather-related, says Deb Brown, University of Minnesota extension horticulturalist. A combination of a severe winter followed by an extended hard freeze in early April caused initial terminal leaf buds to freeze. Trees had to produce new leaves from secondary leaf buds and this accounts for the delay. I had several red oak trees that suffered the same plight - their initial leaf buds froze and the small leaves shriveled and dried up in mid-May.
Ash trees dropping leaves. The cause is a fungal disease called anthracnose that occurs most springs. Cool, damp weather during May spreads the fungus and ash leaves (along with oak, maple and some other species) turn yellow or brown, or shrivel, and often drop to the ground.
With large trees, prevention and control are nearly impossible, since fungicide must be sprayed on the tree starting at bud formation and continued throughout the spring and early summer. In most cases, it's not worth the bother, as most trees will produce new leaves. If anthracnose occurs too many years in a row, a tree can be weakened to the point of dying.
Bur and white oaks leafing out late. This problem occurred on several mature bur oaks on my property and they are now fully leafed out. The cause apparently was the early April hard freeze that froze the first set of leaf buds; trees had to grow a second set of leaves from secondary buds. These trees are in definite need now of at least two inches of rain - four or five inches would easily soak into our parched ground if it fell gradually over several days.
Bur and white oaks failing to leaf out. Several 100+ year-old oak trees near my home are completely barren or have leaves only on the lower third of the tree. I discussed this problem with Dr. Peter Bedker, Dial U plant pathologist, and he said the problem is fairly common throughout east central Minnesota.
These trees have fallen victim to excessive stress, Bedker says, brought on by two severe winters, two years of extremely hard freezes in early April, and two successive summers of well-below-average rainfall. In Bedker's opinion, these trees will not recover and may as well be converted to firewood.
Vertical splits on trunks of maples. Although homeowners often notice these splits in spring or early summer when they mow their lawns, the problem occurs in late winter when afternoon sun causes trunks of young maples to heat up and then cool rapidly when the sun sets and temperatures drop below zero. The result is vertical splits in the bark. Some of these splits will heal over time. Best prevention is to wrap trunks in November and leave the wrap in place until April.
Worms eating leaves of birch trees. The culprit here is birch leaf miner - tiny worm-like larvae that feed between the leaf surfaces on white (paper) birch. One caller said most of the white birch in Shakopee were infested. Partial defoliation usually isn't fatal, but control is possible if trees are sprayed when larvae first hatch. White birch are considerably more susceptible to birch leaf miners than river birch.
Trees dying near house. In most cases, the cause is construction damage. I'll save my sermon on this subject for another column, but suffice it to say that any contractor who doesn't do everything possible to protect tree roots from severance and compaction should be publicly flogged.
Spruce trees dying from bottom up. Colorado blue spruce are susceptible to rhizosphaera needle cast and cytospora canker fungal diseases. Rhizosphaera is more common and kills needles and branches from the bottom up. The disease is most common in low and damp areas where moisture evaporation is slow. Prevention is possible if chlorothalonil, a protective fungicide, is sprayed every spring when new needles are half elongated (early June) and again when needles are fully elongated (early July). White spruce are moderately resistant and Norway spruce are resistant to rhizosphaera needle cast.
Young trees dying. In a spring like this year's, I'd suspect inadequate moisture first. We're in a drought (1.9 inches of rain at my house since the snow melted!), and young trees need to have their roots soaked once a week until they're established. While you're at it, let the hose run once a week around the base of more mature trees, too, at least until we get a soaking rain.
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