What is Sudden Oak Death?

As you might guess from its name, Sudden Oak Death (SOD) is a sudden Oak killer. The disease often lives quietly in the tree for the first 1-3 years of infection without showing obvious symptoms. Then suddenly, the entire tree canopy can turn brown and die in 2-4 weeks!SOD is currently found in Northern California and spreading to Southern California & Southern Oregon. It has already killed over 1 million Oak trees and thrives when there’s more rain and moisture. With all the rain we had this past year, it’s feared that SOD was busy spreading faster and into new areas.

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Sudden Oak Death Symptoms
Check your Oak trees for these most common symptoms:

  • Discolored trunk & branches
  • Oozing sap
  • Leaf spots
  • Canopy dieback

The most sure fire way to know if your trees are infected is to get a lab test. Your Arborist can also provide an assessment and send in lab samples for you.
SOD_diagnosis

Left to Right: Discolored trunk, oozing sap, leaf spots, and canopy dieback.

Oak Species at Risk of SODBlack Oak, Coast Live Oak, Red Oak, Shreve Oak, and other Oaks from the Red & Intermediate Groups

Why Sudden Oak Death Creates Risks
Without a doubt, SOD is an issue when it kills your trees! But beyond that, here are some more causes for concern:

  • Branch and tree failures
  • Liabilities
  • Removal costs
  • Loss of wildlife habitat
  • Dead trees encourage wildfires!

After months of warmer weather, Oak trees are more likely to get stressed and succumb to SOD. And one of the last things you want now is dead, dry trees that add to wildfire fuel!
SOD_risks

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Sudden Oak Death Treatment
Using fungicides is only half the battle. The other half is having healthy trees. Healthy trees are stronger and have better defense against SOD! Here's what you'll find in our SOD prevention treatment.1) Phosphoric Acid

  • Fungicide & immune system stimulator

2) Biochar

  • Soil amendment to improve nutrient & water retention and tree health

3) Essential

  • All-natural source of nutrients & organic matter for better tree health
oak_before_after

Untreated oak (left) and 1 year after treatment (right).

Pro Tips
In addition to applying treatment, here are a couple more things you can do!

Remove other SOD Hosts

SOD also infects and is spread by plants other than oak trees. To minimize disease spread, remove the following plants within a 30 ft radius of your oak tree

SOD Hosts

Arrow Root, Azalea, Bay Laurel, Camellia, Peeris, Rhododendron

Avoid Heavy Pruning in Spring

Spring weather encourages spore spread and new infections, so hold off on heavy pruning. Small cuts are fine, but cuts 4" or larger are best done after spring.

Remember, ideal treatment time is fall, right between Halloween and Christmas, so get your trees treated before the busy holiday season.

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About the Author:

Sophia Huang is a Certified Arborist with the International Society of Arboriculture (ISA). She also holds a Qualified Applicator License (QAL) from the California Department of Pesticide Regulation. Sophia received a Bachelor of Science in Environmental Sciences from Santa Clara University, CA. Discovering her passion for urban trees, she went on to earn a Master of Science in Environmental Horticulture from Cal Poly, San Luis Obispo, CA. Her studies and research focused on urban tree identification, biology pedagogy, and using leaf traits as predictors of tree drought tolerance. She has peer-reviewed publications in The American Biology Teacher and Urban Forestry and Urban Greening. 

Sophia joined the A Plus Tree team in 2019 as an Urban Forest Specialist and is now their Marketing and Education Leader. Her role includes training the team and educating clients on urban tree care – tree pruning, planting, removals, pests, diseases, fertilizers, irrigation, and more! She also writes for the A Plus Tree blog and helps run their Tree Health Care program. 

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