Citrus growers, packers discuss disease threat


Issue Date: August 24, 2016
By Cecilia Parsons
Kenneth Freeman of Laux Management in Porterville cleans citrus leaves and branches from a hedging and topping maching before it leaves a grove for another location. Thoroughly cleaning equipment represents one tactic for preventing spread of the Asian Citrus psyllid.
Photo/Cecilia Parsons
Bob Blakely of California Citrus Mutual notes growers’ comments during a meeting where citrus growers and packers discussed ways to slow the spread of the Asian citrus psyllid into the San Joaquin Valley, and hold off the fatal citrus disease the psyllid can carry.
Photo/Cecilia Parsons

What will California citrus growers and packers prepare to do to eradicate a pest most have never seen themselves, and fight a disease they have only read about?

Meetings held at three San Joaquin Valley locations last week sought to determine the actions growers and packers will take to stop the spread of the Asian citrus psyllid into the state's top citrus-production region.

Huanglongbing, the fatal citrus disease the tiny pest can carry, has devastated Florida citrus production and threatens California citrus. Though the disease—also known as HLB or citrus greening—has not been found in California commercial citrus, it has been detected in more than two-dozen residential citrus trees in Southern California.

"We're trying to gauge growers' knowledge about ACP and HLB and what they are willing to do to slow down infestation," said Nick Hill, a Tulare County citrus grower and chairman of the Citrus Pest and Disease Prevention Program. Hill was one of three speakers who engaged in discussion with growers during a meeting in Visalia. He said he believes citrus growers are facing the reality of the serious threat the psyllid poses.

Calling HLB "a 'death sentence' for California citrus," the grower organization California Citrus Mutual is asking everyone involved in growing, packing and shipping California citrus to take action to slow the psyllid's spread and prevent HLB from invading commercial groves. The organization said the fight against the pest/disease combination has reached a critical point.

Increasing numbers of the psyllids have been trapped in recent months along the Highway 99 corridor. Neil McRoberts, a University of California, Davis, plant pathologist and panelist at the meetings, said the overwhelming likelihood is that psyllids are coming into the valley on bulk citrus shipments from infested areas.

Tarping bulk loads of citrus moving out of quarantine areas, wet-washing fruit in the field and treating fruit prior to harvest are all mitigation measures required in compliance agreements to move citrus fruit out of quarantine areas. But speakers said different levels of compliance by growers, packers and shippers, plus lack of enforcement, have allowed the psyllid to hitchhike its way north from infested parts of Southern California.

Hill said there have been reports from packers and shippers about a lack of equipment for field-washing fruit and concerns about the time and cost to tarp bins of fruit on trailers.

Many growers speaking at the meeting agreed tougher measures should be taken to slow the psyllid invasion.

The area-wide management plan for coordinating psyllid treatments in the San Joaquin Valley has had varying degrees of success with grower cooperation, and CCM President Joel Nelsen said all growers and packers need to be vigilant about fruit movement.

Area-wide psyllid treatment coordination by growers is one of the strategies already in play. Grower liaisons work with other farmers in their area to synchronize psyllid treatments. That strategy is more effective, speakers said, because psyllids readily move from treated to untreated citrus.

All forms of citrus plant material moved out of a quarantine zone are under scrutiny. That includes leaves in bins of citrus fruit; nursery stock and budwood; and leaf litter that accumulates on topping and hedging machines.

Citrus-growing areas of Riverside, San Bernardino and Ventura counties are infested with the psyllid. The California Department of Food and Agriculture continues to test live catches to determine if the insects carry HLB.

CDFA treats residential properties adjacent to commercial citrus, if 75 percent of the commercial citrus is being treated as part of an area-wide management program. Residents can opt out of CDFA pesticide treatments, but Victoria Hornbaker, citrus program manager for CDFA, said nearly all are cooperating and allowing their property to be treated. In addition, releases continue in infested residential areas of a wasp that parasitizes the psyllid.

Presently, the only mandatory portion of the program is removal of trees that test positive for HLB. Hornbaker said most residential homeowners with infected trees on their property are cooperating with tree removal. Those who aren't, receive a visit from law enforcement officers, who have a warrant to remove the tree.

Hornbaker said CDFA's main focus is to find and remove HLB-infected trees. The agency is surveying citrus trees in psyllid-infested areas in Los Angeles County. Any citrus tree that tests positive for HLB will be removed and destroyed.

As for shippers that do not have proof that requirements for the compliance agreement have been carried out, Hornbaker said CDFA could turn trucks around at Castaic. They can also pull compliance agreements, so shippers may not ship fruit until mitigation measures have been taken.

Nelsen and others agreed that early detection technology for HLB infections is a key to removing sources of the disease. McRoberts said experience in Florida shows that for every tree found infected, there are up to 10 infected trees nearby that aren't detected. Reliable tests that find 95 percent of trees are at least a year away, McRoberts said.

Mexico remains a source of HLB infection, he noted, so he said it is not a matter of if the disease moves north via infected plant material or psyllids, but when.

Nelsen said CCM, other grower organizations and CDFA are preparing a response plan to address HLB in California.

Grower assessments are funding education and eradication efforts and the U.S. Department of Agriculture is also helping fund the fight to protect California citrus.

Additional grower/packer meetings are scheduled in Santa Barbara next week, and in Santa Paula, Riverside and Palm Desert in September, to discuss strategies for prevention of HLB. Dates and locations can be found at www.citrusinsider.org.

(Cecilia Parsons is a reporter in Ducor. She may be contacted at ceciliaparsons8@gmail.com.)

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