Two insects threatening health, appearance of Rancho Santa Fe citrus trees

By Joe Tash

Two tiny pests that feed on citrus trees pose a big risk to Rancho Santa Fe and surrounding areas, including increased fire hazard, diminished property values and a blight on the region’s scenic appeal.

Rancho Santa Fe alone is home to an estimated 60,000 to 80,000 citrus trees, mostly lemons, said Chuck Badger, owner of R.E. Badger and Sons, a local company that manages groves and agricultural lands for property owners.

The pests in question are the diaprepres root weevil, also known as the citrus root weevil, and the Asian citrus psyllid. Adult weevils feed on the leaves of citrus trees, while the larvae do the most damage, burrowing underground and eating the tree’s roots, said Badger.

The psyllid poses the biggest risk, because it can carry a bacterium called huanglongbing, a disease fatal to citrus trees. Huanglongbing, or HLB, means “yellow shoot disease” in Chinese. So far, the bacterium has not been found in San Diego County, although it has been detected in Los Angeles County. The Asian citrus psyllid itself is present in San Diego County.

Commercial groves in Rancho Santa Fe, Olivenhain and other parts of San Diego County have been treated for the pests for some time, said Badger, but untreated backyard citrus trees could provide a foothold for the pests.

“It’s the backyard trees that haven’t been treated at all for weevil or psyllids that have us concerned,” said Badger.

Badger and officials with the Rancho Santa Fe Fire Protection District have recently addressed the Committee on the Natural Environment, part of the Rancho Santa Fe Association, to raise awareness about the pests.

Changes in weather patterns have given the pests traction, allowing them to spread more rapidly, said Bill Beckman, chairman of the environmental committee.

“We need to respond to shifts in the weather … and do the right thing to reduce the fire hazard and the spread of diseases, and consider the aesthetic impact of dead and dying trees on our beautiful community. People need to be thinking about these things,” he said.

Treatment to control both pests costs about $6 to $8 per tree, said Badger.

A twice-yearly regimen of treatment is recommended to control both the root weevil and Asian citrus psyllid, said Enrico Ferro, a Valley Center avocado grower who serves as grower liaison for San Diego County for the California Department of Food and Agriculture.

Those treatments, in late winter and late summer, together not only reduce the spread of psyllid, but kill other pests, and improve the health and appearance of backyard citrus trees.

“It really knocks out all the bad guys before the spring flush,” when new leaves sprout on citrus trees, Ferro said.

Some companies offer a reduced price when a number of homeowners in a neighborhood have their trees treated at the same time, Ferro said.

The Asian citrus psyllid is particularly dangerous because the bacterium that it can carry kills trees, and is not curable. In Florida, he said, HLB has wiped out more than half of the state’s citrus groves.

“It’s important to everybody,” he said. “We don’t want to let this pest take over.”

The bugs have already damaged local groves. In Rancho Santa Fe, the fire protection district has sent out more notices in recent years to homeowners, requesting them to remove dead or dying citrus trees, said Conor Lenehan, fire prevention specialist and forester.

While some homeowners have elected not to water their groves because of the escalating costs of water, in other cases the weevil and psyllid have damaged the trees.

“The dead and dying orchard becomes a huge fire hazard,” said Lenehan. “It puts their structure in greater danger — it’s harder to defend from a fire.”

Ferro recommended two websites for those who want to learn more about the Asian citrus psyllid and how to manage the pest: citrusinsider.org and ucanr.edu/sites/acp.

In addition, the San Diego County Farm Bureau website offers a list of licensed pest control businesses that can treat for root weevil and Asian citrus psyllid. Find the list at https://www.sdfarmbureau.org/ACP/PCB.php. Contact the farm bureau at 760-745-3023.