First discovery of citrus disease tests state's plans


Issue Date: April 4, 2012
By Kate Campbell
The citrus disease known as HLB causes symptoms including leaf mottling; here, symptoms are seen on grapefruit leaves.
Photo/ J.M. Bové, INRA Centre de Recherches de Bordeaux, Bugwood.org

Saying they have plans in place, government and private officials began response this week to the first discovery in California of a lethal citrus disease.

Agricultural inspectors fanned out across the Los Angeles County suburb of Hacienda Heights after a backyard citrus tree and an Asian citrus psyllid tested positive for the incurable citrus disease known as Huanglongbing or citrus greening.

Pest treatments began in the area last week, immediately after confirmation of the disease, and arrangements were made for the tree's removal.

HLB disease had not been previously detected in California, although psyllids have been found in a number of Southern California counties since 2008 and quarantines are in place. The psyllid has carried the disease in other locations where HLB has attacked trees. The infecting bacteria were confirmed in a psyllid sample and plant material taken from a grafted lemon/pummelo tree in a residential neighborhood of Hacienda Heights.

The disease has caused widespread damage to commercial citrus groves in Brazil and Florida. It was detected in Texas citrus in January.

The advancing threat prompted California citrus experts to begin developing rapid response plans in 2006 and growers, processors and shippers have funded laboratory facilities for rapid testing of psyllids and plant tissue for the pathogen.

"We have plans in place that address every scenario. Now we've got our game face on and we're going to get on with it," said Ted Batkin, president of the California Citrus Research Board.

California Department of Food and Agriculture Secretary Karen Ross said the department is moving swiftly to protect the state's citrus growers, as well as residential trees and the many citrus plantings in parks and other public lands throughout the state.

"We have been planning and preparing for this scenario with our growers and our colleagues at the federal and local levels since before the Asian citrus psyllid was first detected here," Ross said.

HLB bacteria attack the vascular system of plants in the citrus family, but do not pose a threat to humans or animals. The psyllid can spread the bacteria as it feeds on citrus trees and other related plants.

Once a tree is infected, there is no cure. Trees typically decline and die within a few years. The disease also can be spread from infected trees to other citrus on budwood that is grafted onto new rootstock.

Experts call HLB the world's most devastating citrus disease. Symptoms of a diseased tree include yellow shoots, with mottling and chlorosis of the leaves. The juice of the infected fruit has a bitter taste and the fruit's skin may retain some green coloration even though it is ripe. Infected trees eventually die.

"We have a lot to protect here in California," said Robert Leavitt, CDFA plant health and pest prevention director. "We immediately began surveys for about a half mile around the detection site, looking for other citrus trees that showed symptoms, and began treatment sprays in the area."

CDFA said it has asked the U.S. Department of Agriculture for emergency, expedited quarantine and eradication authority, and said a public meeting was set for Hacienda Heights residents on April 5.

Leavitt said officials were making arrangements to remove and dispose of the infected tree, which he called an "essential" step. CDFA also placed a hold on the shipment of all citrus nursery stock within five miles of the detection site.

Helene Wright of USDA said a federal investigation unit traveled to the community to try to figure out where the infected tree originated and to determine the need to close any pathways for diseased plant material to enter the state.

"We also work closely with the county and the state to help prevent host materials from moving out of the quarantine area, except under some very specific circumstances," Wright said.

Commercial citrus growers are well aware of the threat, Batkin said.

"What we are telling the public is that we need to continue our diligence in our detection systems to find infected trees early so they can be dealt with," he said, adding that there "undoubtedly" are more infected trees that have yet to be identified.

"The events that infected the single tree we're working on now more than likely occurred in numerous locations of the state," he said. "We have long predicted that the bacteria exist, and more than likely in Southern California. This is a given. It's what has happened historically around the world."

Now, Batkin said, the approach to the disease discovery is to put out the message to residential property owners that HLB will kill their trees and those of their neighbors, and therefore infected trees must come out.

"We're asking homeowners to help us find the psyllid and reduce the populations so it doesn't move the bacteria around," Batkin said.

CDFA said treatment for HLB will be conducted with the oversight of the California Environmental Protection Agency and will be conducted safely, with advance and follow-up notices provided to residents in the treatment area.

Officials said if Californians believe they have seen evidence of HLB in local citrus trees, they should call the toll-free CDFA pest hotline at 800-491-1899. For more information on the Asian citrus psyllid and HLB, visit www.cdfa.ca.gov/phpps/acp/.

See related story, spinach genes may help citrus trees resist fatal disease.

(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at kcampbell@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.