June 4, 2019

Preventing Phytophthora Crown Rot In California Almond Orchard

The Challenge

The incidence of Phytophthora Crown Rot has increased dramatically over the last five years in tree orchards across California. Lower quality soils are often at the highest risk, and once disease symptoms are visible, it spreads aggressively. When a large almond producer came to Trace Genomics to test their orchard the objective was clear- find if they had the disease, and if so, identify management practices to mitigate their risks. The Orchard Manager had run other tests, including the ELISA, but because this test is not species-specific, their results were inconclusive.


The Solution

The Orchard Manager worked with Trace Genomics to perform a soil analysis of pathogen and soil health levels. The orchard was able to identify and quantify the levels of different Phytophthora species in their orchard’s blocks including:

  • Phytophthora cinnamomi
  • Phytophthora cactorum
  • Phytophthora cambivora
  • Phytophthora cryptogea
  • Phytophthora nicotianae
  • Phytophthora parasitica

Trace identified and quantified the different Phytophthora species in each sample and found high levels of Phytophthora cambivora in trees that were not showing symptoms. This factor was compared to the soil health indicators where Trace’s analysis found the aerobic to anaerobic ratio was low. These values are associated with waterlogging.

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Beyond Phytophthora the analysis measured other soil borne pathogens and identified low, non-harmful, levels of Pythium, Verticillium, and Armillaria. The soil health indicators showed normal nutrient and carbon cycling as well as normal oxygen levels.

Results From Trace Genomics

As a result of Trace’s soil analysis, the orchard managed the harmful species before Phytophthora Crown Rot was visible in their trees. Equipped with the findings, the Orchard Manager modified the irrigation schedule and adjusted the Metalaxyl levels to reduce inoculum levels in the soil. The orchard will continue to monitor the non-harmful pathogens (Pythium, Verticillium, and Armillaria) over the next season. Through these actions, the orchard prevented their risk of disease and protected their yield.

To find out the underlying issues in your orchard, email us at marketing@tracegenomics.com