ARS | Publication request: Phytosanitary Status of California Citrus

Submitted to: Society of Citrus Nurserymen International Congress
Publication Type: Proceedings
Publication Acceptance Date: October 1, 2008
Publication Date: N/A

Interpretive Summary: The citrus industry in California has been relatively free of serious citrus diseases for decades due to the efforts of the University of California and the California Department of Food & Agriculture. The Citrus Clonal Protection Program (CCPP) is the backbone of a registration system that provides pathogen-tested, true-to-type budwood to the industry. This has resulted in a very low incidence of non-vectored diseases of citrus. The most important vectored disease of citrus in California is tristeza, caused by the Citrus Tristeza Virus (CTV) and vectored by various aphids. The Central California Tristeza Eradication Agency (CCTEA) monitors the production areas of citrus in California for the presence of CTV. Positive trees are removed. This has resulted in a very low incidence of tristeza in California. Although the current health status of California citrus remains high, there are various threats to this status. These threats include diseases of citrus exotic to California, notably Huanglongbing, as well as potential changes in the transmissibility of endemic CTV strains.

Technical Abstract: The California citrus industry continues to maintain a high phytosanitary status, albeit one with serious external threats. Propagative materials in California originate with the Citrus Clonal Protection Program, a University of California program that provides pathogen-tested, apparently clean base materials. The use of CCPP-derived materials ensures that newly planted trees are in a high-health status. Two vector-transmitted pathogens, Citrus tristeza virus (CTV) and Spiroplasma citri, are endemic in the production area. CTV is currently managed in certain areas under a program (Central California Tristeza Eradication Agency) with the goal of identifying and removing CTV-positive trees. The functioning of this program ensures that CTV incidence is very low (< 0.1%) in participating districts. Other pathogens such as Citrus psorosis virus and various citrus viroids are also present but only at low incidences. CCPP-derived propagative materials have been tested for specific exotic pathogens and are apparently free. Threats to the continued healthy status of the California industry include exotic diseases, particularly Huanglongbing, and potential changes in the transmissibility of endemic CTV strains.