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Joseph F. Boggs, Ohio State University Extension, Hamilton County/Southwest District; James A. Chatfield, Erik A. Draper, |
Examples of Treeage Categories
Insect and mite galls provide good examples of Treeage Category 1 problems. Ash inflorescence galls are caused by the eriophyid mite, Eriophyes fraxinivorus. While these conspicuous brownish, lumpy, and unsightly galls look like small witches' brooms growing just beneath the leaves, only the flower parts are affected, so no real injury is done to the tree.
The bright red, globose, pouch-like bladder galls caused by the eriophyid mite, Vasates quadripedes, on the upper leaf surfaces of red and silver maples are another good example of a Category 1 mite gall problem.
There are more than 800 types of galls that may occur on oaks. However, only two are considered damaging to the host. Woolly leaf galls are a good example of a very apparent oak gall that causes no damage to the tree.
As its descriptive name implies, the woolly leaf gall looks like someone stuck a dense wad of light brown wool to a leaf vein. The galls are produced by the cynipid wasp, Andricus fullawayi, and are found on the underside of leaves where they are usually attached to the midvein, although they occasionally arise from lateral veins. They range in size from pea-sized to the diameter of a quarter.
When oak leaves turn color in the fall, the galls often detach and fall to the ground. Large numbers littering the ground beneath an oak tree may cause concern, but no harm has been done to the tree.
Tar spots are a good example of a Category 1 disease. In their book, Diseases of Trees and Shrubs, Sinclair, Lyon, and Johnson open their description of these diseases with the sentence, "Tar spots are among the most showy and least damaging foliar diseases." In summer, the fungus produces shiny, 1/4 to 1-inch diameter black spots on the upper leaf surface. The disease gets its name from the tar-like appearance of the spots. Indeed, as with many Category 1 pest problems, looks can be deceiving.
Dutch elm disease connects two beetles with fungi to produce a Treeage Category 2 problem. The native elm bark beetle, Hylurgopinus rufipes, and the European elm bark beetle, Scolytus multistriatus, are both capable of vectoring the fungi, Ophiostoma ulmi and O. novoulmi. These disease-causing fungi eventually cause xylem vessels to become incapable of transporting water. For almost all intents and purposes, once infected, American elms will die regardless of attempts to control or remove the infected parts.
Cultural problems may also be sorted into Treeage categories. A mature maple tree that has been badly "topped" and is in severe decline is a good example of a Category 2 problem little can be done to restore the loss of vigor that usually follows this destructive pruning practice.
Eastern tent caterpillar (Malacosoma americanum) is a good example of a Category 3 problem. This insect shows-up early in the spring, produces webs between branch breaks, and feeds on newly expanding leaves. High populations of caterpillars can completely defoliate trees, requiring the tree to expend energy to refoliate.
Common bagworm (Thyridopteryx ephemeraeformis) is another Category 3 problem. Season-long feeding by this defoliator may strip needles and kill branches on conifers or entire trees. Both insects can be controlled with properly timed insecticide applications.