Farm Progress

If the citrus disease Huanglongbing is found in California, in residential or commercial citrus, there will be mandatory tree removal and area-wide treatment to knock down ACP in residential and commercial citrus. California would be the first state to take this approach in the fight against ACP and HLB.

Cecilia Parsons, Contributing Wrter

March 12, 2012

4 Min Read

California’s agriculture department will take on a formidable foe in an effort to protect the state’s $2 billion dollar citrus industry.

In an announcement at the March 8 Citrus Showcase in Visalia, CDFA’s director of Plant Health Inspection, Robert Leavitt, said the trapping and detection activities for Asian citrusp will shift to the state on April 1. The proactive move, according to Leavitt, is to put regulatory muscle in the program.

The Citrus Research Board has been the lead agency in the ACPtrapping and detection as well as educational outreach to urban areas. Asian citrus psyllid, vector of the deadly citrus disease, Huanglongbing, has a foothold in the east Los Angeles area and has been found in a total of five Southern California counties. The disease, also known as citrus greening, has not been found in California. Both ACP and HLB are present in Florida where the industry has lost 200,000 acres of citrus. Worldwide, the disease has infected more than 100 million trees. There is no cure for HLB and trees not removed eventually die. Fruit from infected trees is small and misshapen.

Leavitt also announced that if the citrus disease Huanglongbing is found in the state, in residential or commercial citrus, there will be mandatory tree removal and area-wide treatment to knock down ACP in residential and commercial citrus. California would be the first state to take this approach in the fight against ACP and HLB.

“Area-wide treatments and removal are key to the eradication,” Leavitt told citrus growers.

“This is the difference with Florida, they started too late; here we’re going to be proactive.”

Leavitt said CDFA is committed to working with the citrus industry and fighting ACP “tree by tree, grove by grove.”

According to Joel Nelsen, president of California Citrus Mutual, the recent discovery of HLB in Texas triggered the change in lead agencies. Other changes include a redirection of treatment efforts to better protect commercial citrus.

Sampling for HLB will be done in areas where ACP populations are heaviest. Leaves from suspect trees are tested and there is now a 48-hour turnaround time for results. Leavitt said homeowners would be notified that the state would remove their infected trees. They would not be compensated, but there has been discussion of replacing the citrus tree with another type of tree. All plant material would be chipped and taken to a landfill. In the case of commercial citrus, infected trees would be burned or chipped depending on the location. All citrus trees adjacent to infected trees would be tested for the disease and removed if necessary. Florida lost their fight with HLB because they did not mandate removal of residential trees, leaving the infection to spread.

Parasitic wasps

Citrus grower Nick Hill applauded the ongoing efforts to combat ACP. For the last three years, the strategy has been to knock down populations and conduct an educational outreach to urban residents. Hill said that effort has been very successful with a nearly 100 percent acceptance rate for spraying back yard citrus trees where ACP has been detected.

Hill heads the Citrus Pest and Disease Prevention Committee, formed by the state legislature in 2009 to develop a citrus pest and disease work plan. The committee is also charged with setting the carton assessment to pay for the trapping and spraying as well as the outreach programs. Currently, growers pay 9 cents per 40-pound carton to fund the program. Budget for 2011 was $15 million.

Last year, 72,809 residential sites were treated and 11,000 yellow sticky traps were placed in urban areas. There were 2,800 samples of ACP tested for the HLB virus and 1,000 tissue samples tested.

In other states with ACP populations, the HLB virus was detected about five years after the pest was first discovered.

The situation for California citrus growers is scary, Hill admitted, but he believes that with mandatory tree removals plus continued ACP suppression, they have a fighting chance.

Leavitt said the state is reaching out to organic growers in an effort to help them keep their certification if chemical control is necessary in their groves. If effective organic-approved sprays are available they could be used instead, he said.

Potential for bio control of ACP is another positive result of work by UC researchers. Mark Hoddle of UC Riverside brought back two species of parasitic wasps from Pakistan in 2011 and recently received clearance to release one specie — Tamarixia. The wasps target ACP.

Since release, Hoddle and other researchers are trying to determine if Tamarixia are reproducing in the field.

Richard Stouthamer of UC Riverside told growers that the mass-rearing process for the wasp in the laboratory is aimed at genetic diversity that will result in hybrid females being released.

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