New Blight Alarms California Olive Growers

The California olive indus­try has been alerted to an alarm­ing new dis­ease that appears to be spread­ing among olive cul­ti­vars com­monly used for oil pro­duc­tion. At a recent board meet­ing of the Olive Oil Commission of California (OOCC), it was reported that the pathogen Neofabraea had been observed on both Arbosana and Arbequina trees.

The dis­ease is akin to ​“bulls eye rot” in apples and pears being grown in the pacific Northwest. The pathogen was pre­vi­ously iden­ti­fied by U.C. Davis researchers in Sonoma County on olive fruits at two com­mer­cial orchards in Sonoma County in 2013, affect­ing the Coratina and Picholine vari­etals.

The newly affected region includes the Sacramento Valley and Delta: Glenn County, just north of Sacramento, and San Joaquin County to the south. Symptoms include defo­li­a­tion, twig lesions, and leaf spots, and both humid grow­ing areas and El Nino appear to pro­vide favor­able envi­ron­ments for the dis­ease.

“It’s new to California and it’s alarm­ing, for sure,” said Florent Trouillas, a Cooperative Extension spe­cial­ist in plant pathol­ogy at U.C. Davis. ​“It appeared out of nowhere. This is def­i­nitely some­thing the indus­try needs to be pre­pared for.”

Trouillas said the research on Neofabraea, specif­i­cally focus­ing on olive oil olives, was ini­ti­ated this past spring in the San Joaquin area where it hass been recur­rent. ​“It’s quite seri­ous when you find the dis­ease has affected entire rows of trees. And we haven’t yet vis­ited any groves where table olives are grown.”

The OOCC research com­mit­tee is now into the prob­lem and fund­ing is likely to be sought to inves­ti­gate the rot and its biol­ogy and come up with solid strate­gies that grow­ers can imple­ment to con­trol it.

Given the dev­as­ta­tion caused by the Xylella fas­tidiosa pathogen that has rav­aged more than a mil­lion olive trees in south­ern Italy over the past two years, the boom­ing California olive oil trade should be on high alert as more is learned about the new blight.