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Don't Let Disease Kill Off Your Beautiful Trees

Tree diseases can be fatal and spread quickly between trees. Removing the dead trees often doesn’t fix the problem, since the infection will generally have already spread to surrounding trees. Two common tree diseases in West Michigan are Oak Wilt Disease and Beech Bark Disease.

Oak Wilt Disease

What is Oak Wilt Disease?

Oak wilt disease is caused by a fungus that plugs the water-conducting system of oak trees. To block the spread of the fungus, trees produce gums and resins which also plug the system, causing infected trees to die quickly. Oak wilt disease is mainly a problem of red oak trees, which can include the group of northern red oak, black oak and pin oak. These trees will die within just a few weeks of becoming infected. White oaks are more resistant so the disease will progress slower.

How Does Oak Wilt Spread?

Diseased trees pass the fungus to adjacent healthy trees through root grafts. The fungus can also be carried to other areas by sap-feeding beetles, which carry the fungus spores from infected trees to freshly wounded (pruned) healthy trees. The fungus can also be spread in firewood. Infected firewood can form spore-producing pads under the bark which attract sap-feeding beetles. The beetles will feed from those pads and can transfer oak wilt spores to healthy trees, sometimes miles away. Trees become infected when the spores enter fresh wounds in the bark.

How Can You Prevent Oak Wilt Disease?

If you have plans to trim your oak trees or cut down some limbs, be sure to hold off between April 15th and July 15th, and just to be safe, even after July 15th. Sometimes a tree wound can’t be prevented, such as if high winds cause a branch to break. And some cases, wounding a tree is accidental, such as a lawn mower or equipment damaging the bark. Prevention is as easy as being aware of your surroundings to not accidentally damage the tree, and to hold off from pruning between mid-April and mid-July.

Controlling the Spread of Oak Wilt

Controlling the spread of the oak wilt fungus between healthy and infected trees is simple in theory but difficult and expensive in practice. To avoid spreading the fungus, root grafts must be severed between healthy and infected trees. Simply cutting down the tree is not an effective way of stopping the fungus from spreading, because the fungus stays alive in the root system and can spread to healthy trees. Cutting down an infected tree before the root grafts have been severed can actually speed up the movement of the fungus to surrounding trees.

Beech Bark Disease

What is Beech Bark Disease?

Beech bark disease is caused by an infestation of very small insects called beech scales. These insects are only about one millimeter long and feed on the trees sap. An infestation can be identified by a white waxy appearance from the beech scales secretions. The infestation is devastating and generally overwhelms a tree. The second part of the disease is that when the beech scale facilitate the introduction of Necteria fungus. This infection will then create tarry spots which ooze a brownish fluid. It is possible for the tree to save itself by isolating the infected area but the sheer magnitude of most beech scale infestations are so great, it gives the tree little hope of survival.

How Does Beech Bark Disease Spread?

In the past, the most prevalent spread of the disease is the beech scale insect being carried by wind and birds that have them on their feet and feathers. In more modern times, the spread of the disease is more often due to firewood that is being carried between areas.

How Can You Prevent Beech Bark Disease?

Individuals can help the control the spread of beech scales by not transporting firewood from place to place. Also, removing diseased beech trees can salvage other trees and may reduce the insect population, to allow resistant or partially resistant trees a better chance of survival.

Controlling the Spread

Because of the volatility of the fungal-infection, there is no sure-fire way to control the disease once a tree has been infected. One way to help is to control the beech scale population. Insecticides are not a viable solution as the insect has a shell that protects it from them. Scientists have had some success applying dormant or horticultural oil multiple times which deprives the insects of air. Also, injections of certain insecticides into the trunk or root of the tree has show some success.

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