UC Delivers

Research on new celery virus identifies control measures

The Issue

From 2007 to 2009, celery crops in coastal California were damaged by an apparently new problem. Affected plants showed extensive yellowing and deformity of the leaves, as well as distinct, large brown to tan elongated lesions on the petioles. Such petiole symptoms prevented the celery from being marketable and resulted in crop losses of up to 40 percent. The symptoms were striking in appearance and did not match those caused by any known celery pathogen in California. The disease was first detected in Santa Clara and Monterey counties and later was found in Ventura County.

What Has ANR Done?

UC Cooperative Extension farm advisors initiated an investigation and assembled a collaborative team that included the California Celery Research Board, USDA-ARS researchers, and the California Department of Food and Agriculture. They determined that the problem was caused by the viral pathogen Apium Virus Y (ApVY). This was first report of ApVy virus on celery in North America. In order to develop control strategies for celery growers, the team conducted research into the biology of ApVY, including nature of the virus pathogen, means of spread, host range, natural reservoirs of the virus and susceptibility of celery cultivars.

The Payoff

Research on new virus results in control measures for celery growers.

Researchers conducted field surveys and found that the virus was present in several central coast and south coast counties. While celery was the most severely affected crop, related plants such as parsley and cilantro were also infected. A key finding was the discovery that poison hemlock, a weed that is also in the Apiaceae plant family, was widely infected and appeared to be a reservoir source of the virus. Inoculation studies using many celery cultivars revealed that some selections were less susceptible and developed only limited symptoms. Importantly, ApVY is not seedborne in celery. Based on these studies, growers were advised to remove or otherwise control the poison hemlock weed; if such steps are not possible, celery plantings should be moved to different areas. Aphids spread the virus from the weeds to celery, so spraying for and managing this insect is important. Highly susceptible celery cultivars should not be planted in places having a history of ApVY problems. Some tolerant cultivars are available and were used by growers. The adoption of some of these measures may account for the significant reduction of ApVY incidence in 2010.

Contact

Supporting Unit:

Steven T. Koike,(831) 759-7350, stkoike@ucdavis.edu
Oleg Daugovish, (805) 645-1454, odaugovish@ucdavis.edu