How to diagnose, treat damage to trees

09/27/2013 3:28 PM

09/28/2013 9:22 AM

We dodged one bullet with all the rain that followed all the drought this summer: Most trees did not succumb to root rot, Jason Griffin of the John C. Pair Horticultural Center said. The subsoil was so dried out from the drought that it was able to accept the heavy rain that fell during the summer.

But many trees are suffering and will continue to suffer from the effects of drought, while others show the damage of diseases and insects, or of other afflictions that are man- or weather-induced.

Dail Hong of Hong’s Landscape & Nursery said he was working in one neighborhood this week where half the red maples were suffering from sunscald, drought stress and borers, and the top of the trees had died out because of it.

“It’s not one problem – it’s three different factors,” he said.

Tree damage can become apparent quickly but more often takes its time to become evident, meaning that it’s a good idea to regularly monitor your trees so that you can detect problems as soon as possible.

When you note something that doesn’t look right – holes in or spots on leaves, missing bark, debris under the tree – scour for any evidence of possible causes, such as tiny insects on the undersides of the leaves.

One comforting thing for people at this time of year is that while fall is a time for planting, it isn’t the time to try to correct insect or disease problems, extension agent Bob Neier said. Trees are starting to shut down for winter and have done most of their photosynthesis, so it won’t help them at this point to treat them. (Evergreens that keep their leaves are another story.)

Next spring, after the weather has warmed up fully and trees have a chance to start growing again, you can assess damage.

If you need help diagnosing a tree problem, there are several options. You can take samples to a garden center or to the Sedgwick County Extension Center at 21st and Ridge Road. If you note a problem with leaves, for example, don’t bring in a pile of leaves, extension agent Bob Neier said. Instead bring in a branch that’s a foot or so long with leaves attached. If possible, bring examples of the problem in the phases that it’s displayed (how it started out and progressed), he said. Also note what part of the tree is affected. Photos on your cellphone or printed out also can help with a diagnosis.

Or call a certified arborist. Some charge for a diagnosis, and some don’t, so call around for rates and availability. For people who aren’t regular customers, arborist Jeff Otto of Longhofer Lawn & Tree Care says that a visual inspection can run $35 to $50, unless it requires getting up high in a tree, in which case it costs more. He said that the money helps cover the costs of continuing education for arborists.

Here are just a few of the problems you may be seeing on trees; see photos for some other examples.

String-trimmer damage

Accidentally hitting the base of a tree once with a string trimmer might be OK, but persistent weed-whipping is the result of ignorance or apathy and can lead to the death of a tree, arborist Jeff Otto said. Keep areas under trees grass-free and mulched.

Drought

Can show up as all kinds of stress, including small leaves and a thin canopy.

Bark damage

“I’ve seen a lot of maples but others too that have bark damage and scorch especially on trees 4 inches diameter and under,” Neier said. That’s from sunburn on the west side of the tree, where you can see telltale peeling off of the bark. If at least three-fourths of the bark is intact, there’s a chance the damage can heal over, Neier said.

The care you want to give such a tree applies to other young trees, too: Remove the grass about 3 feet out around the tree, put wood chips down, and fertilize with a tree fertilizer at the label rate once the tree starts losing leaves, usually in late October. “If it’s in a well-fertilized lawn, you won’t need to fertilize the trees, too. That should be sufficient.”

Squirrel damage

Squirrels can strip bark from a tree, causing damage including dead leaves in the canopy. There’s no good solution. You can try pepper spray, but you have to be able to get it all the way up to where the squirrels are feeding, and anytime it rains, you have to spray again, Neier says. Squirrels can also be trapped, but then you have a live squirrel to dispatch.

Twig dieback on oak

“Recently we have seen twig dieback on pin and other oaks caused by a fungal disease called Botryosphaeria canker,” Ward Upham of K-State writes in K-State’s Horticulture 2013 newsletter. “Affected trees show wilting or flagging of terminal growth on the ends of branches. Dieback usually extends 4 to 6 inches down the twig, with leaves bending back toward the twig before turning brown. Dead leaves remain attached to the tree. If you look closely at the twig, you should see a rather marked transition from healthy to diseased tissue. Take a knife and scrape away some of the outer bark tissue. Healthy tissue is light green. Diseased tissue tends to be brown to black.

“Botryosphaeria canker differs from oak wilt in that only the tips of branches are affected. Oak wilt affects whole branches. This disease causes such minor damage that chemical control measures are unwarranted. Dead twigs on small trees may be pruned off if desired.”

Mycosphaerella leaf spot on ash

A wet summer often produces an outbreak of Mycosphaerella leaf spot on ash trees, Upham said. It displays itself in small brown spots that can grow to blotches and can cause a tree to drop its leaves early. It may look bad, but it does not hurt a tree, he said.

On the horizon: emerald ash borer

Emerald ash borer, an insect that has killed millions of ash trees in the East and parts of the South, has been detected as close as Johnson County in Kansas and is not a threat in the Wichita area yet as far as we know.

Certain insecticides can be applied to valuable ash trees to try to prevent emerald ash borer damage, but the Department of Agriculture doesn’t recommend treatment unless ash trees are within 5 miles of where the borer has been found.

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