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    Oak Wilt

    Oak Wilt: is a disease that enters the vascular system of Oak trees and kills them rather rapidly.  Obtained from current research, the Red Oak family tends to be the most susceptible to this fungal infection.  The Red Oak family consists of Red Oak, Pin Oak and Northern Pin Oak.  Oaks in the White Oak family, also, are able to contract the disease but can sustain a much longer lifespan with the disease, usually 2-3 years.

    Signs of Oak Wilt:  The first signs, that will be visible, can be noticed in the canopy of the tree.  Leaves will begin to wilt, turn dull, and then begin to turn a yellow or brown color.  Wilting begins at the end of the branches where leaves will begin to shed and is most prominent in the crown during the early stages.  This process usually takes place during early summer and sometimes as early as May.  Since this disease is very aggressive the process of declination takes place rapidly.  If the tree is in the Red Oak family it can die off in as quickly as 1-2 months, and on average it will take only one summer.  Trees in the White Oak family have been known to last several years, with only a few branches dying per year.

    Spread of the disease: Being that the fungus becomes a part of the tree by traveling through its vascular system; it makes it very easy to spread the disease to other trees.  The quickest and most common transfer of Oak Wilt is through root grafts.  A root graft is the intermingling and connection of roots, which typically will only take place between trees of the same species. However, there have been a few cases where trees of opposite species have created a root graft.  Oak Wilt can also spread through pollination.  Spores are created and released through the sap of the tree, which attracts insects, more specifically “picnic beetles”, which will then collect the spores from the infected tree and carry them to healthy trees.  This transfer is less common, because in order for the spores to enter the tree there has to be an open wound on the tree. This is why pruning or removal of oak should only be done during the dormant seasons, November-February, to help prevent future spreading.  The “picnic beetles” are at their highest abundance during the growing season May-July and are still slightly active during the months before the first frost.  Transporting firewood can also aid in the spread of this disease to other surrounding areas.  The department of Natural Resources forestesters advise holding oak firewood fore several years before transporting it.

    Prevention:  Currently there are no cures for trees that have already been infected, there are only preventative measures that can be taken to reduce and eliminate the spread.  These methods consist of; the removal of infected trees, and then burningc, burying or covering the trees with plastic, and trenching around the infected trees.   Trenching needs to be done 4 feet deep to insure that any root grafts that have been made are severed.  Treatment is another preventive measure that can be taken to keep the fungus from infecting an Oak tree.  The treatment currently used is a fungicide that is injected directly into the living oak tree.  With one treatment, Red Oaks will remain symptomless for up to 2 years.  However, this treatment can be expensive, so it is typically only used on high value trees.

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