Celery growers and pest control advisors working with celery and related crops are advised to be aware of a new virus disease on celery.
In 2007, a few commercial celery plantings showed symptoms that were not typical of the common viruses that are occasionally seen in celery.
Symptoms on lower leaves were variable and could consist of yellow or brown line patterns, yellow blotches, brown lesions, mosaics, or in some cases distorted and twisted leaflets. Celery petioles could exhibit brown, sunken, and elongated lesions.
In 2008 the virus problem reappeared and has been confirmed in Monterey and Santa Clara counties.
When celery sap was examined under an electron microscope, thread-like virus particles were observed. Further research using molecular methods indicated that the celery was infected with a virus named Apium virus Y (ApVY).
This is the first report of California celery infected with ApVY. However, ApVY may not actually be new to California. In 2003, cilantro plants from fields in California showed mosaic, vein clearing, and stunting symptoms. The virus in the cilantro was also identified as ApVY.
Very little is known about ApVY. This pathogen has been reported on Apiaceae weeds in Australia and celery in New Zealand. The virus is aphid borne.
Other aspects such as host range, whether it can be seedborne, detailed characterization of the virus itself, and how the disease develops still need additional investigation. Our research in 2008 already identified a possibly important alternate host of ApVY, the weed poison hemlock.
The occurrence of this novel virus illustrates that new, emergent plant pathogens occasionally show up in California, and that vigilant observation and accurate diagnoses are called for in such situations.
The resulting research effort now in place also demonstrates the benefits of multi-agency teamwork, as University of California, USDA-ARS, California Department of Food and Agriculture, and the celery industry are partnering together to gain an understanding of this new problem.