oak tree disease
Oak Tree
oak tree diseases

Oak Tree Disease

Oak trees can be infected by several different diseases and pests. Some problems can affect all Oak types, while other malicious organisms prefer certain oak tree variants. There are also several diseases capable of infecting many different unrelated tree species from various families. Two of the most common oak tree diseases are Oak Wilt and Sudden Oak Death. In older specimens, dry rot can be a problem.

Oak tree disease – Oak Wilt

Oak Wilt is an oak tree disease caused by an organism called Ceratocystis fagacearum. Ceratocystis fagacearum is a fungus closely related to the three Ophiostoma fungi responsible for Dutch Elm Disease.

The Ceratocystis fagacearum fungus originated somewhere in eastern Russia and was spread throughout the world by human trade. Today, it is for instance a severe problem for oaks growing in eastern and central United States where it is present from Virginia to Minnesota and Arkansas. You can however find occasional oak wilt infections all the way down to Texas. Red oaks seem to be especially vulnerable to this oak tree disease. When white oaks become infested, they usually show more resilience and infested white oaks typically lives considerably longer than infester red oaks.

When an oak becomes infected with this oak tree disease, the tree will try to block any further spreading of the fungi by closing its own cambial tissue. This blockage will however also prevent water and nutrients from being delivered throughout the tree and the oak will eventually die.

Oak tree disease – Sudden Oak Death

Sudden oak death is a caused by an organism called Phytophthora ramorum. This oak tree disease is a water mould infection and there is still no known cure. Phytophthora ramorum is not only able to infest several oak species; it can kill several other tree and shrub species as well. Certain plants, such as rhododendrons and California Bay Laurel, will not die from the infection; the symptoms will be limited to non-fatal leaf problems.

The symptoms of this oak tree disease vary between different oak species. When Tan Oaks become infested, the first sign will for instance usually be wilting new shoots and old leaves that loose their colour and become pale. In Black Oaks and Coast Live Oaks, the first symptom of this oak tree disease will instead usually be a dark red or tar-black, slow flowing sap that bleeds from the surface of the bark.  

We do not know when and where this oak tree disease originated, but Phytophthora ramorum was found in European nursery Rhododendrons and Viburnum during the early 1990’s. As mentioned above, there is no available cure for this oak tree disease. Recent studies have however showed that regular wildfires might reduce the risk of Sudden Oak Death.

Oak tree disease – Dry rot

Older oak trees can be susceptible to dry rot. Dry rot can be caused by several different fungi, including Serpula lacrymans, Poria incrassata and Merulius lacrymans. The fungi infest the woody parts of the oak and break down the cellulose. It is not only oaks that can suffer from dry rot; virtually any piece of wood can become infested by fungi, including wood used in furniture or as building material. An old oak infested with dry rot may not show any exterior signs of poor health and this oak tree disease is therefore usually discovered after a strong storm when the entire oak has been brought down.

 

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Copyright 2005 oak-tree.info. Pictures based on a picture by wikipedia user MPF
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oak tree disease