Farmers cautious after virus found in residential citrus
So far, no new quarantines have been triggered. It’s unclear how agricultural officials handled the infected trees. Hornbaker said CDFA and USDA re- main in “an information-gathering stage.” She noted the state has been surveying “the core area” around the detection site in Tulare County and will expand its sur- vey activities to Fresno and Kings coun- ties in the coming months to determine the extent of the virus. Key citrus stakeholders—including growers, regulatory officials of citrus-pro- ducing states, industry representatives
and residents of private property that CDFA has surveyed—have been informed about the virus detection, Hornbaker said. In addition, USDA has informed Japan and Taiwan, both of which import California citrus fruit. “Fruit is not a pathway for virus spread,” Hornbaker said, “and these countries have not expressed concerns.” Matt Watkins, director of farm opera- tions for Bee Sweet Citrus, a grower-pack- er-shipper in Fowler, said some of the
By Ching Lee California citrus growers are on the lookout for a new disease threat to their orchards. The U.S. Department of Agriculture has confirmed findings of citrus yellow vein clearing virus, or CYVCV. It was first de- tected in March in residential citrus in the city of Tulare during routine tree surveys by the California Department of Food and Agriculture. It represents the first discov- ery of the virus in the United States. The virus has not been detected in commercial orchards, CDFA said. “We’re still learning a lot about it,” said Imperial County farmer Mark McBroom, who chairs the state Citrus Pest and Disease Prevention Program. CDFA describes the virus as “a disease of quarantine significance to the United States,” as it can lead to “significant eco- nomic losses” and “cause serious damage to most citrus species” by diminishing fruit marketability. It has also been re- ported in grapes, beans and weeds. Before being found in Tulare, the dis- ease was restricted to Pakistan, India, Iran, Turkey and China, where it is in nearly all citrus-producing areas, ac- cording to CDFA. The virus is transmitted by aphids, in- cluding the green citrus aphid, cowpea aphid and melon or cotton aphid. The cit- rus whitefly also is a vector. Plants become infected as insects feed on the foliage. The virus is so called because leaves of in- fected young lemon and sour orange trees show a water-soaked appearance and yel- low, clear veins on their front side. The leaves may also display crinkling and warping. Symptoms vary depending on citrus va- riety, viral strain and environmental con- ditions, especially temperature, according to CDFA. Some infected trees show irreg- ular ringspots on leaves and mosaic-like patterns on the fruit. The virus can be as- ymptomatic in some cultivars. In infected lemon and sour orange trees, CYVCV is less pronounced in the summer. In severe infection, the fruit is malformed, and trees die back. Tulare County Agricultural Commissioner Tom Tucker said there are protocols for invasive pests and dis- eases. But with CYVCV being new to California and the U.S., federal and state officials have yet to determine an appro- priate response. Victoria Hornbaker, CDFA director of the Citrus Pest and Disease Prevention Division, said the department “continues to conduct intensive delimitation surveys to better un- derstand the current presence and poten- tial impacts of CYVCV.” This work will help CDFA and USDA develop “an appropriate regulatory approach,” she added. Because the virus is spread by insects that are known to be present in California, McBroom said it “makes it much more challenging to get your arms around it,” as eradicating the vectors “would be next to impossible, if not impossible.”
What’s encouraging, he said, is that CYVCV doesn’t appear to be “as detri- mental as HLB,” referring to huanglong- bing, or citrus greening, which eventually kills the trees. With CYVCV, fruit from the infected residential trees remains edible and “doesn’t appear different”—at least in the early stages—even though their leaves display symptoms, McBroom said.
See CITRUS, Page 9
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