Concern mounts as citrus pest threat increases

Issue Date: November 12, 2008
Kate Campbell

Daniel Arena, a state pest control specialist, uses a backpack vacuum to check for Asian citrus psyllids at a San Diego County nursery. Asian citrus psyllids can carry a disease that causes mottling damage to foliage and renders fruit inedible.

San Diego County nurseryman Mark Collins watched anxiously as a state pest detection specialist vacuumed his citrus trees. The new procedure helps officials find elusive Asian citrus psyllids—non-native pests that can carry a very serious plant disease, citrus greening.

Since the pest isn't attracted to conventional traps, finding it can be hit or miss, unless populations have grown to considerable size. So, to improve the chances of finding psyllid infestations early, officials have added vacuuming to their existing trapping and inspection protocols.

The first Asian citrus psyllids found in California turned up in traps in late August, near the Sweetwater Reservoir in San Diego County. That triggered an immediate state and federal quarantine in the area. Now, host plants may not be moved out of the 1,200-square-mile quarantine zone—transporting cut greens, green waste and citrus fruit also is strictly regulated.

Last month, another Asian citrus psyllid infestation turned up in Imperial County, about 100 miles away from the San Diego infestations. The psyllids were trapped in a citrus grove and residential areas near the Mexican border.

So far in southern San Diego County 12 psyllid infestations have been found on residential properties within the quarantine zone and they have been treated at residential sites. No infestations have been found at commercial locations, and none of the psyllids trapped in California have carried citrus greening disease.

The psyllid, shown in extreme close-up, has been found in two Southern California counties.

Three of Collins' seven Evergreen Nursery operations are within the San Diego County quarantine zone. Collins said he can only sell citrus trees for local landscaping within the designated quarantine area.

These days his nurseries are hung with pest traps, plants are tagged and numbered and continuously inspected—for the psyllid and other damaging, non-native pests that plague San Diego County agriculture.

"We have four retail outlets and the psyllid restrictions on citrus alone have cost us many thousands of dollars," said Collins, who operates the county's largest retail nursery business.

But he said the seriousness of this pest and the disease it can spread warrants an aggressive response. Experts agree and say citrus greening disease may be the most serious citrus disease in the world.

The disease currently is devastating Florida citrus groves. The value of the 2007-08 Florida citrus crop fell 19 percent to $1.2 billion, due in large part to the impact of citrus greening disease.

There is no cure once a citrus tree is infected with the bacterial disease and Florida farmers are bracing for further, significant production declines in coming years.

Because this pest and disease threat are so significant, leaders of California's $1 billion a year commercial citrus sector are taking steps to address the problem. Growers are voting now on a per-box assessment to support research on the pest and the disease it can spread.

They've also been meeting with U.S. and Mexican officials to discuss a coordinated response to the threat, since the psyllids already infest many locations in Mexico.

"As our colleagues in Florida have sadly experienced, this pest and the disease are devastating," said Mike Wooten, vice president of corporate relations for the Sunkist Growers citrus cooperative. "It's nothing less than catastrophic. By their own estimates, within five to seven years, the citrus industry in Florida will no longer be viable."

The only long-term hope is research, citrus growers say. The concern, however, is that it may take too long to find a solution to save California citrus production.

To help fund emergency research, Wooten said citrus growers are voting on an increased assessment on production. Currently, growers are assessed at 3 cents per 60-pound field carton. Funds go to the California Citrus Research Board.

The vote should be completed in the next few weeks under the direction of the California Department of Food and Agriculture. If passed, the maximum assessment would be 9 cents, but initially growers probably would be assessed at 5 cents a carton.

"We're recommending our growers support the increased assessment," Wooten said. "Obviously it's a financial cost, but it's a self-protection tool we absolutely must have."

Wooten said citrus groups and farmers have asked the U.S. Department of Agriculture to set up a cooperative effort with the Mexican government to treat for the psyllid on both sides of the border. Treatments reportedly have started in Tijuana.

A delegation of U.S. citrus leaders traveled to Mexico City last month to encourage a cooperative approach to attacking the pest. Leaders representing U.S. citrus production agreed to share research and control plans with their Mexican counterparts and meet again in December.

The states of Texas, Georgia, Mississippi, South Carolina and Alabama have all detected the Asian citrus psyllid but not the citrus greening disease, also known as huanglongbing or HLB. Florida and Louisiana have both the pest and the disease.

"Everyone who grows citrus on the North American continent is at risk," said Ted Batkin, president of the California Citrus Research Board.

Meanwhile, at Evergreen Nursery in San Diego County, Mark Collins hunches over the bag of vacuumed material from citrus trees in his nursery and looks carefully at what was found—some leaves, a ladybug, dust. He says he's relieved that nothing threatening has turned up yet, but knows that could change quickly.

"Containing and eradicating pests is a high priority," Collins said. "I don't want any bad bugs around, to say the least. It's a real worry."

For online information about the Asian citrus psyllid and citrus greening disease, see

(Kate Campbell is a reporter for Ag Alert. She may be contacted at

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