According to a blog post by the Olive Oil Commission of California (OOCC), several board members have reported evidence of a new disease that appears to be affecting California olive trees.
Below are pictures by University of California Plant Pathologist Flourent Trouillas, which illustrate symptoms in twigs and leaves from infected orchards that may help growers determine if this problem occurs in their olive orchards.
According to Trouillas, the putative pathogen, known as Neofabraea, was initially reported in ‘Coratina’ and ‘Picholine’ cultivars in two commercial orchards in Sonoma County in 2013.
OOCC board members report it is being found in some orchards located in the Sacramento Delta growing areas on ‘Arbosana’ and possibly ‘Arbequina’ varieties, and may be more prevalent in humid growing areas.
It is apparently related to the “bulls-eye rot” pathogen in apples and pears. Symptoms in olive include defoliation, leaf spots, twig die-back, and twig lesions.
The OOCC Research Committee will be looking at this problem and may consider funding of research to investigate the pathogen identity and biology, as well as control strategies for this new disease.
In the meantime, growers are encouraged to take a look at the photos below to help determine if this disease is present in your orchards. If you believe you see evidence of this new disease, the OOCC recommends you contact your local University of California Cooperative Extension farm advisor.