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Sudden Oak Death, first reported in 1995 in California, is a rapid decline and death of oaks due to a newly identified fungus, Phytophthora ramorum. The fungus causes bleeding bark cankers on the trees -- the cankers are reddish-brown to black and “bleed” red to black sap.

Pest of the Month: Sudden Oak Death

By Jesse Lee


 

Los Padres National Forest Sudden Oak Death mortality. — Photo by California Oak Mortality Task ForceWhat does it look like?


Sudden Oak Death, first reported in 1995 in California, is a rapid decline and death of oaks due to a newly identified fungus, Phytophthora ramorum. The fungus causes bleeding bark cankers on the trees — the cankers are reddish-brown to black and “bleed” red to black sap.


Infected trees show a decline in health, most notably a significant browning of the leaves, within four weeks. Actual tree death is more prolonged, sometimes up to two years after infection.


 


Host material and range


P. ramorum infection and the resulting Sudden Oak Death occur throughout California and southern Oregon on tanoaks, coast live oaks and California black oaks. The fungus also attacks other hosts such as Camelia, Rhododendron, huckleberry and bay laurel.


Because other trees and shrubs are so susceptible to P. ramorum, the fungus could potentially spread throughout the United States.


 

Bleeding canker, Monterey County. — Photo by Ian Smith, University of Melbourne


Current threat


Since the first reported cases of Sudden Oak Death, the disease has destroyed tens of thousands of oak trees. The cankers caused by the fungus split the bark and lead to death while the crown dies back — the leaves turning rapidly from green to brown.


Once weakened by the fungus, the tree is open to infection from secondary diseases, causing even faster death.


 


Prevention tips


Ensuring that trees are healthy — with plenty of nutrition and water for increased vigor — remains one of the best options for prevention of Sudden Oak Death. In addition, proper care and precautions should be taken so as not to spread the disease.


 


Treatment tips


There is no cure for Sudden Oak Death, but there are a variety of treatment steps that can be taken to help manage and control the disease.


Fungicide treatments can help boost the trees’ natural defenses and vigor, protecting the trees from infection and slowing the rate of disease progression. A phosphite treatment can be injected or sprayed and should be applied in fall or spring, within two months of infestation, for best results


 

Tanoaks with Sudden Oak Death. — Photo by Steve Tjosvold, UCCE Santa Cruz 


What can you do?


More information on Sudden Oak Death, including signs to look for, treatment and prevention tips and research can be found at the California Oak Mortality Task Force Web site at www.SuddenOakDeath.org  


Jesse Lee is with Epic Creative, Wis. Article provided by Mauget, a leader in micro-injection and micro-infusion tree care. Contact Mauget or visit www.Mauget.com to learn more about Sudden Oak Death, steps taken to prevent and control it, and proper fungicide application and use.

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