Updated: May 8, 2019
...not caused by the west-coast, sudden-oak-death (SOD) pathogen - that's what I am seeing in east TN, this spring and summer. I've seen it primarily on red oaks but it occurs on white as well as pin, tulip poplar, elms and lot more. One disease will show browning leaves that drop in the wettest part of spring and summer. The other disease will show browning leaves that stay on the tree in the heat of summer. Both symptoms come on suddenly and the tree can die within the year or even a few weeks. You can treat if caught early enough - so call me if you see the symptoms below in either the spring or late summer!! Supplemental watering is critical to help oaks that are suffering and to deal with the drought we have had in TN several summers now. Even if your oaks' do not have SOD or oak wilt but the pervasive anthracnose - they can succumb if also being hit with drought multiple years. More than 2 weeks without rain during the growing season - I recommend supplemental watering.
There are SEVERAL diseases called 'oak wilt' and often used synonymously with 'oak scorch'. There is no way to determine what microbe is causing the disease without laboratory work (e.g. PCR/fingerprinting or growing the disease in a lab for microscope evaluation). Some microbes are more responsive to treatment than others; all are chronic meaning re-treatment is necessary and the lifetime (longevity) of the tree is likely reduced. A combined chemical treatment and biofertilizer is how I approach this disease. No treatment can EVER be guaranteed. We are dealing with complex systems. How long has the tree been infected? By which organism is it infected? Are there multiple infections? Is there other non-visible tree damage? Has the tree suffered chronic bad nutrient access due to soil conditions or planting location? These are questions that can't be answered without very expensive equipment, laboratory analyses, and/or very invasive probing. BTW - I recently sent a sample to a pathology lab that used only visual exploration of the leaf material to diagnose. This time of year (spring) plants can be asymptomatic. They don't show the bacterial or fungal disease symptoms. Infection can only be determined through molecular or chemistry-based (ELISA) approaches. Insist on having this kind of work done. It's what we are paying for!
Research on the bacterial caused Oak Leaf Scorch (the deadly one) shows that prolonged tree survival is increased by up to 7% with the combination of beneficial microbes and antibiotic treatments.
Please note, photographs are from University of Maryland Extension Service.
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