Saturday, May 19, 2012

Tree Disease in Eastern Ontario ~ Oak Wilt


Oak Wilt is a fungal disease, quite similiar to Dutch Elm Disease,  though more easily manageable, left unattended it can easily and quickly kill off your trees.  It affects all Oak types but is highly susceptible to the Red Oak family of trees who offer the disease the least resistance.

It was first discovered in 1944, in Wisconsin, and its highly believed that it originated in the USA as no other countries have been able to track the path of origin to any other source.  Though reputed to have been around since the early 1900's, it wasn't until the mid~1980's the the threat began to gain a firm foothold into the Oak tree family, as more people turned to building their homes in Oak woods.

Beetles that carry the Oak Wilt fungus do not have chewing mouth parts and they require some method of an open wound entry so that they can invade.  Hardwood vascular wilt diseases prevent water from essential areas of the tree by blocking the system needed to transport nutrients.  Oak trees will often produce tyloses, those balloon~like growths found on the tree which aid in blocking off of pathogens and prevent infections from spreading, doing such, inadvertently destroys the tree as essential nutrients are also blocked from reaching their source.

Fungus Mat
Early symptoms include wilting leaves from the top of the tree which will spread downwards, oftentimes the leaves will turn bronze in colour, appear water~soaked at they begin to fall off their branches, as well as, discoloration of the vascular tissue, brown streaks or spots that can be seen under the bark into the sapwood.  Depending upon the environment and Oak tree type, a normal death will usually occur within two to six months.

OWF is spread in two ways:  the transfer of spores from diseased to healthy trees by insect vectors and the transferal of the disease by root grafts.  If the conditions are right, after the tree dies, spores are created on fungal mats that form under the bark of the tree.  A~sexual spores called endoconidia, which are barrel shaped produced in chains, will form waiting for compatible mating types.  When this performance occurs sexual spores called ascospores are produced, which because of their fruity fragrance, draws certain types of sap beetles to visit, feed and breed, thereby picking up the fungal spores.  The symbosis between fungus and insect acts in the transmission of infecting otherwise healthy areas of trees that are unable to be affected by root grafts.

Root grafting is the number one method of the diseases' spreading, as trees within 50 feet of an infected tree can easily be infected, creating a chain~reaction that can only be broken with proper care and treatment.

If you believe you have discovered this disease in your Oak trees, please call a professional tree specialist to handle your needs.  The cutting and removal of the Oak tree can cause devastating affects on the other Oak trees you may have in your area by accelerating the root grafting; without the host to continue feeding, the disease will find the next source and this could become costly on many levels as whole groves of trees can become infected and die.





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