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California prepares for citrus greening

The California citrus industry is preparing for the deadly Huanglongbing disease (HLB) or citrus greening, and its primary vector (carrier), the Asian citrus psyllid (ACP).

Since the first psyllid was detected in a residential backyard near the Sweetwater Reservoir in San Diego County late last summer, 1,300 psyllids have been captured in San Diego and Imperial counties, according to the California Department of Agriculture (CDFA). CDFA has placed quarantine restrictions in the two counties.

Fortunately, all psyllids captured thus far in California have tested negative for HLB. The ACP feeds on citrus tree leaves and stems to spread the infection. HLB symptoms include lop-sided fruit, plus yellow, splotchy leaves. Infected trees eventually die. Researchers are working to develop HLB-resistant cultivars.

ACP and HLB have not been found in Arizona though the psyllid’s arrival is expected soon in Yuma County. It is several years after psyllids outbreaks are detected before HLB symptoms appear.

California’s 290,000-acre, mostly fresh-market citrus industry is valued at about $1.3 billion. Arizona’s 63,000 citrus acres produce about $63 million in annual income.

California officials have worked closely with Florida citrus leaders to glean information about the pest and disease’s destructive path across the Sunshine State’s 30 citrus-producing counties.

Florida officials discovered the first psyllid in 1998. Citrus greening was confirmed in 2005.

Florida leaders share tales of missed opportunities, destruction, and large financial losses from ACP and HLB. Michael Rogers, University of Florida entomologist, estimates that 3 percent to 4 percent of Florida’s citrus trees have HLB. Some trees have been removed.

ACP-HLB was an all-day topic in late March during the 93rd annual meeting of the Entomological Society of America (ESA) – Pacific Branch, where Florida and California citrus specialists provided the latest pest and disease details.

MaryLou Polek, vice president of operations, California Citrus Research Board (CRB), Visalia, Calif., outlined a list of accomplishments thus far for the California ACP-HLB Task Force formed in 2006.

The task force co-chairs include: Ted Batkin, CRB president; and Larry Bezark, who previously served as the CDFA Plant Health and Pest Prevention Services assistant director. Bezark currently is the CDFA Integrated Pest Control branch chief.

Polek most recently served as a CDFA plant pathologist and previously headed the agency’s citrus tristeza eradication program.

The task force’s steering/administrative committee is comprised of Joel Nelsen, California Citrus Mutual; Jim Cranney, California Citrus Quality Council; Mike Wooten, Sunkist Growers; Beth Grafton-Cardwell, University of California (UC); Helene Wright, USDA; Robert Dolezal, California Association of Nurseries and Garden Centers; plus Polek.

The group will determine overall goals and objectives, gather and organize the information provided by individual committees, act on the recommendations formulated by the committees, and produce a document (action plan) for use by state and federal officials.

The comprehensive plan will address pest and disease exclusion, early detection, and eradication of the Liberibacter species causing Huanglongbing disease and the insect vectors.

“We knew that if the Asian citrus psyllid was found in California that we needed to move fast,” Polek told the entomology group. “We have examined the needed pesticides and applied for special use permits.”

The science and technology committee is currently developing a regional management plan where California, Arizona, Texas, and Mexico citrus leaders will share ACP/HLB information.

Pest and disease battles require large financial war chests, Polek says. The USDA’s Animal and Plant Health Inspection Service’s Citrus Health Response Program is allocating more than $5 million to the cause. Some of those dollars are funding CDFA/USDA trapping, survey, and detection programs, plus pesticide treatments in Mexico.

The CRB is providing dollars through the board’s current assessments on boxed fruit. Growers last fall voted to increase the assessment from a nickel up to nine cents per box.

The seven, producer-initiated California pest control districts established in the 1940s are another funding source. The districts self-manage pest issues and have the authority to survey and remove or treat infected trees, Polek says. Five districts are located in the San Joaquin Valley, plus two in Southern California.

Another pro-industry effort is to form a state pest control district with the intent to form a pest and disease management control agency. The idea is to level the playing field for the California citrus industry so that each grower pays equally for ACP-HLB management programs.

“The long term goal is to support the USDA and CDFA’s roles to combat pests and pathogens in citrus,” Polek said. “We’re not here to take over their activities but to augment their efforts.”

CRB plans include a statewide program to educate and train personnel in ACP detection and HLB disease symptoms.

“The mantra is educate, educate, educate,” Polek said. “We plan to detect reservoirs of HLB-associated pathogens, collect as much plant material and as many psyllids as possible, and test it all. We want to make homeowners part of the solution.”

CRB will establish three testing laboratories: located at the San Diego County agricultural commissioner’s office, San Diego; the grower-owned Central California Citrus Tristeza Eradication Agency, Tulare, Calif.; and near the University of California (UC), Riverside campus. Questionable samples would be sent to a USDA-certified regulatory lab.

“Riverside is an excellent location for a lab,” Polek said. “As UC Riverside researchers develop different citrus-based diagnostic methodologies and technologies, the lab can develop the technology transfer to deliver the benefits to growers.”

The labs will test for multiple citrus diseases.

The CRB’s ACP-HLB focus will be commercial citrus, Polek says. Backyard citrus issues will be left to the CDFA. CRB will deploy GPS technology for all trees and tested samples; information will be maintained in a central database.

“Our goal is to generate a bar code for every tree where a trap is placed and where insect and plant tissue samples are collected,” Polek said.

CRB has created a draft database with trap, tree variety, and root stock information from about 50 fields.

CRB is basing its direction on the lessons learned in Florida and countries including Brazil.

“We want to look at the mistakes made by Florida and not walk down the same path,” Polek said.

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