Joint Conference of the International Organization of Citrus Virologists XXI and
the International Research Conference on Huanglongbing
March 10-15, 2019
Georgios Vidalakis, chair of NCPN-Citrus, has been recognized by the American Phytopathological Society for his outstanding contributions to regulatory plant pathology and crop security. Read more at the link below:
- The citrus industry worldwide is being challenged by the spread of Huanglongbing (HLB), a graft-transmissible disease associated with species of the bacterium Candidatus Liberibacter, which is vectored by the Asian citrus psyllid (ACP), Diaphorina citri.
- NCPN-citrus has grown to include 10 centers in 9 US states and territories with citrus foundation blocks maintained in protective structures to exclude ACP and HLB and other vectors and citrus diseases.
- NCPN support allowed high throughput citrus diagnostics to flourish, which in return led to the increased availability of pathogen-tested citrus propagative materials, thus reducing infection rates in commercial citrus and promoting the use of NCPN produced materials among citrus enthusiasts and hobbyists.
- NCPN supports the Citrus Clonal Protection Program (CCPP) at the University of California, Riverside, the citrus center that was the birthplace of basic citrus therapy and bioindexing technologies, establishing a citrus germplasm model system adopted by all citrus centers around the world.
- To prevent the spread of citrus diseases, always use trees produced by licensed reputable nurseries that are using NCPN-produced pathogen-tested citrus propagative materials. Do not move citrus trees or tree parts within or into the US.
“Four Wind Growers is a four-generation old family-owned citrus nursery based in Watsonville, California, with additional growing grounds in winters, CA. In 1946, a curious soon-to-be nurseryman named Floyd Dillon decided to develop a California version of the dwarf apple and pear, and chose citrus. Floyd learned that researchers at UCLA and UC Riverside were already experimenting with new varieties and different rootstock-scion combinations to improve disease resistance, production, control tree size or modify other characteristics. Dr. Bill Bitters and other citrus researchers worked with Floyd to create dwarf trees that had attractive foliage and tasty fruit. After several years of experimentation, Floyd founded Four Winds Growers.
Today, dwarf citrus is a common sight in nurseries throughout the West and is grown successfully in containers throughout the world. The adaptability of dwarf citrus to container growing has made them increasingly popular outside of traditional citrus growing areas. They are most easily moved indoors for winter protection and outdoors in the warm seasons. In addition, dwarf citrus has become important to gardeners whose gardening space is limited to patios, balconies and small porches.
We have a four-generation experience from our nursery indicating that the only way to run a citrus nursery business properly is to use clean stock material and for this reason we source our material from the Citrus Clonal Protection Program (CCPP) at the University of California. Clean nursery stock is the foundation for any kind of clean plant systems. We propagate the trees and make so many each year that if we were using infected materials we would spread infections very quickly. Starting with clean plant material is therefore vital for any downstream agricultural operation to be successful.
At Four Wind Growers, we also have a long history of testing the trees, starting in the old days when Tristeza was spreading and causing great losses, and more recently with the HLB threat in California. This is very important as we keep monitoring our plant material and make sure that what we use is clean. Support from NCPN allows us to test trees that are inside the screen house using new testing methods, and giving us an opportunity to identify and eliminate potential problems as early on as possible in the citrus production chain.
Thanks to the CCPP and NCPN, an even more robust common plan was developed in recent years for California, giving us high levels of confidence in our material because of where it is sourced. A proactive approach from NCPN and the nurseries gave us opportunity to act before HLB becomes a problem in California.
As we look to the future, it is ever more attractive to be able to obtain plant material from the CCPP as the CCPP is currently collaborating with Florida to import rootstocks that appear to be HLB tolerant. The importance of these programs in providing clean plant material is paramount as nurseries will be able to receive new varieties to combat HLB and have confidence that they are clean.
In a broader sense, having access to new varieties and varieties of special interest from a trusted source such as the CCPP is part of the strategy to prevent the spread of diseases, as the CCPP assists in importing and cleaning these varieties making it possible to bring them to market. The availability of clean budwood of new varieties has allowed us to maintain competitiveness for four generations, and we currently employ over 50 people.
We appreciate that it is important for the general public and hobbyists to have access to varieties that would otherwise be available only from sources that are not trusted. The first discovery of HLB in California was indeed from a backyard tree made using plant material that had not been pathogen-tested. In a further effort to saturate the market with clean plant stock, we started selling to retailers so that we can provide the general public with clean citrus stock.
Support from NCPN helps us in being a thriving business, currently growing over 250,000 quality dwarf citrus trees for containers and home gardens each year. We also provide over 60 varieties of fine citrus trees, including a selection of rare and unusual citrus that may not yet be available in retail nurseries.”
Nate Jameson, Brite Leaf Citrus Nursery LLC, Florida
“We citrus nurserymen all believe that for our industry to stay profitable, we must start with disease-free plant material as part of controlling our costs and keeping production profitable.”
“…not every citrus producing state has the knowledge base or the programs in place to recognize citrus diseases much less prevent them from spreading. NCPN is a proactive program that works by preventing the spread of disease versus a reactive program that endeavors to remove a disease after it has spread.”
“NCPN is providing the information and support funding and is improving citrus health. This is important funding which will have a long term positive impact toward feeding the world's population into the future.”
On a global scale, one of the most important issues within citrus is the disease known as Huanglongbing (HLB), caused by several species of bacteria (Candidatus Liberibacter spp.) and vectored by phyllids, primarily the Asian citrus psyllid (ACP) (Diaphorina citri). In the U.S.A., the disease has devastated citrus production in Florida and is now threatening other citrus growing regions within the network. In April of this year, NCPN-C chair Georgios Vidalakis provided an update on the HLB situation at the 20th International Organization of Citrus Virologists Conference in Chongqing, China. The vector was first discovered in San Diego, CA in 2008 and has spread as far North as San Mateo County. This resulted in wide spread ACP quarantine efforts and ACP ‘task forces' to implement control measures in California. The first HLB positive tree was identified in the Los Angeles area of Hacienda Heights in 2012. The second HLB positive tree was not found until 2015 approximately 15 miles northwest of the first positive tree; now 12 additional trees have been identified within this same area. All trees have been removed and destroyed. Collaborative efforts continue in research and ACP/HLB testing within industry, state, and federal entities to combat this threat.
Recent NCPN-affiliated publications on citrus crop viruses:
da Graça, J., Douhan, G., Halbert, S., Keremane, M., Lee, R., Vidalakis, G., Zhao, H. 2016. Huanglongbing: An overview of a complex pathosystem ravaging the world's citrus. IJPB 58:373-387 http://dx.doi.org/10.1111/jipb.12437