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Funding for Diaprepes root weevil control facing budget ax

Chuck Badger believes pending action by the state of California could be penny wise and pound foolish, placing the 400-acre citrus operation he manages in Rancho Santa Fe, Calif. in San Diego County in difficult financial straits.

At issue are the proposed, across the board 10 percent budget cuts for all departments of government designed to offset the state's growing multi-billion dollar budget deficit. In the case of one California Department of Food and Agriculture (CDFA) program, the department plans to cut CDFA control costs for the Diaprepes root weevil (DRW), Diaprepes abbreviatus (Linnaeus), in Southern California by about 83 percent.

CDFA Public Information Director Steve Lyle said, “The proposed budget for 2008-2009 includes a $3.66 million reduction for Diaprepes root weevil activities, which would leave $590,000 for regulatory activities to control the pest.”

Current CDFA funding is spent on eradication (ground treatments), survey (visual and trapping), regulatory compliance, public outreach and research on biological control organisms, and alternative pesticides to use against the various DRW life stages, Lyle said. The funding is spent in Orange, Los Angeles, and San Diego counties. Approximately 75 percent of the funding is spent in San Diego County.

The DRW feeds on the leaves and roots of about 270 plants and trees. San Diego County has the highest infestation of the weevil in California.

About 150 lemon trees valued at an estimated $60,000 in tree and productivity losses have been lost so far on Badger's citrus operation due to the DRW. Badger, president of his company R.E. Badger & Sons, plus the San Diego County Farm Bureau (SDCFB), found his first DRW in an orchard in summer 2006. His concern is that CDFA-DRW funding cuts would trigger expanded infestation and even pricier containment and eradication costs in the future.

“The CDFA and others have conducted studies that show if private enterprise has to pick up the control costs that the weevil will probably spread,” Badger said. “We could be looking at billions of dollars worth of needed treatment if the weevil spreads in California. It's a penny wise, pound foolish decision.”

Current state DRW control efforts are working and should continue, Badger said. Proof of that is fewer DRW adults found in his citrus groves and the end result of fewer larvae.

Badger's sharp eye has seen the DRW cause reduced vigor in infected lemon trees. If weevil funding is cut, Badger is concerned that the control responsibility would shift to the private sector.

“I don't know if we could keep up with the treatment on the farm because of the expense,” Badger said. “I think we would eventually see the loss of a lot of citrus in San Diego (County) and wherever the weevil might spread. I think we have the opportunity to eradicate it right now. If we stop treatment and rely on the private sector, I'm not sure the job will get done.”

San Diego County agriculture has much at stake with the DRW, according to Gary Bender, University of California Cooperative Extension (UCCE) farm advisor, San Diego County. DRWs are found in a fairly contiguous area including Oceanside, Encinitas, Carlsbad, Fairbanks Ranch, and Rancho Santa Fe.

“About 800 production nurseries are in San Diego County and the spread of weevils could result in a quarantine of nursery products. That would be financially devastating,” Bender said. “If a quarantine was placed on a nursery, shipments could be halted for six months while soil treatments are being made.”

DRW adults feed on plants grown for food and as ornamentals. The main food crops affected in California include oranges, grapefruit, lemons, and avocados, although root larvae have not yet been found on avocados.

San Diego County has about 12,000 acres of citrus including about 3,000 acres in lemons. The weevil's taste buds prefer lemon trees.

All citrus along the coast in San Diego and Ventura counties could be at risk, Bender said. Ventura County is California's largest lemon producer. Unlike nursery stock, lemon trees with a DRW infestation can yield marketable fruit since adults and eggs are not found on the fruit.

DRW, also called the citrus root weevil and the sugarcane rootstalk borer, is currently found at 250 find sites in six quarantine areas in San Diego County, 72 find sites in four quarantine areas in Orange County, and 29 find sites in two quarantine areas in Los Angeles County.

DRW treatments began in September 2006 in Los Angeles County and in Newport Beach in Orange County. Treatments began a month later in Newport Beach West and Yorba Linda. San Diego County treatments started on the same dates in varying locations.

DRW factoids

Adult diaprepes root weevils are medium-sized, polymorphic weevils from three-eighths to three-quarters-inch long. The insect always has stripes and features a myriad of colors ranging from orange, yellow, gray, and black. Males are often smaller than the females.

Adults damage the leaves by chewing in semi-circles while the larvae feed on the roots and other below ground plant parts. The weevil is most likely spread by infested plant material since the insect is not a strong flier.

Whitish oval eggs are one millimeter in size and female adults will deposit eggs in clusters of 30-260. Each female may oviposit a maximum of 5,000 eggs. Eggs are laid between leaves and hatch in 7-10 days.

Diaprepes pupae are orange and pupate in a soil chamber for 15 to 30 days. From egg to adult takes five to 18 months. Newly emerged larvae burrow into the soil to feast on underground tree parts. Ten to 11 instars are completed in five to 15 months. Full-grown larvae are c-shaped and whitish.

Adult DRWs emerge after a rainfall or an irrigation event and are most active at dawn and dusk. The female lifespan is about 147 days compared to 135 days for males. Adult damage includes leaf notching and frass pellets.

The DRW entered the U.S. through three separate introductions from the Caribbean into Florida in 1964. Florida's annual losses and control costs in citrus total about $72 million, plus $2 million in vegetables and ornamentals. The weevil arrived in Texas in 2000.

UCCE efforts

Bender's associate in the weevil fight is Loretta Bates, UCCE staff research associate, San Diego County. Both are based at the UCCE office in San Marcos.

“Lemons are where we're seeing a lot of tree death and having to pull out groves,” Bates said. “In terms of cosmetic leaf damage on ornamentals, the DRW feeds heavily on coral and acacia trees in San Diego County.”

A huge unknown is whether the DRW could move northward into the citrus-producing counties in California's San Joaquin Valley where freezes occasionally occur. In Florida, the DRW hasn't moved into the state's northern region. The theory is the tropical insect can't survive cooler temperatures, but that's not been proven.

Another unknown is whether the DRW could cross into citrus groves in the low desert areas of California's Imperial and Coachella valleys, or even further into Yuma County, Ariz.

“I don't think the weevil could tolerate the high heat and low humidity associated with the low desert climates since the Diaprepes root weevil is a tropical insect,” Bates said. “The weevil is taking hold in San Diego County because the climate is closer to its native habitat.”

Bender and Bates are collectively working to study and track the impact of DRW on agriculture. Bates is also conducting educational meetings with farmers, city park employees, and others.

“If you look at a 4-year-old lemon orchard, the Diaprepes root weevil larvae are in the soil eating the roots away,” Bender said. “Once the tree can't pickup water and nutrients due to the damage, the tree starts to lose leaves. You can actually see through the tree's canopy.”

With damaged roots comes the potential for fungal pathogens entering the plant including Phytophtora and Fusarium root rot.

DRW population surveillance equipment used by CDFA and UCCE includes Tedder, cone, and skirt traps — plus sleeve cages.

“The Tedders trap is very effective,” Bates said. “Since these weevils have a strong instinct to crawl upward when they come out of the ground, the weevils think the trap is a tree, then crawl in the container and can't get out. Tedders traps are placed along roadsides along with emergence-type traps.”

Insecticide sprays

According to the University of California Statewide Integrated Pest Management Program, active insecticide ingredients for adult control include bifenthrin, fenpropathrin, carbaryl, cyfluthrin, and cryolite. The active ingredient for larvae control is Imidacloprid, plus two types of beneficial nematodes, Heterorhabditis indica and Steinernema riobrave. Egg control is based on the ingredient diflubenzuron. No known treatment exists for pupae.

CDFA spraying has definitely reduced adult DRW numbers, Bender said. Yet for larvae, results have been disappointing so far. Bender said, “We don't think the chemicals are penetrating down to where the larvae are.” Data collected by Bender and Bates shows that larvae may bury themselves 12 inches under the soil and travel 4 feet out from the tree trunk.

Bender is trying other chemicals with and without beneficial nematodes on the soil around lemon trees to determine if the larvae can be controlled.

The cooperation between UCCE and CDFA on DRW control has been excellent, Bates said.

A portion of the UCCE San Diego's DRW control efforts is funded through a 2007 $56,000 CDFA grant, partly used to fund Bates' research and outreach. Bender has received written notice from the CDFA for additional grant monies in 2008-2009. Bender hopes to hire a staff person to manage DRW control in nurseries. What's unsure is whether the dollars will actually appear given the CDFA-DRW financial cutbacks. Earlier grants were funded by the Citrus Research Board and CDFA.

Biological options

The use of several biological control agents in Florida has shown promising results against DRW including the nematodes Heterohabditis indica and Steinernema riobrave and a fungus Beauveria bassiana. Seventy-eight percent to 91 percent of the egg mortality in 2004 was attributed to Aprostocetus, an ectoparasitoid wasp of diaprepes eggs released from 2001-02.

Appeals to state

In a Feb. 22 letter to Gov. Schwarzenegger, SDCFB President Badger said the DRW-budget situation puts the majority of farmers in San Diego County at risk.

“Now ranked as the 12th largest farm economy among all counties in the nation, farming has an estimated impact to our local economy of $5.4 billion according to the County's Department of Agriculture, Weights & Measures,” Badger said. “Without decisive action here, we fear that that the Diaprepes root weevil will spread throughout California.”

Badger referenced a CDFA report dated Aug. 5, 2007 that concluded the spread of DRW in California could cost citrus and avocado losses to producers and consumers between $1.6 billion and $3 billion annually, and $90 to $102 million annually to nursery producers and consumers.

Badger said an unchecked population of DRWs in California will result in the possible loss of productive farmland, loss of organic farms, damage to farmers and the economy measured in billions of dollars, the need for farmers to apply new amounts of pesticides, and the increased use of pesticides by the public.

San Diego County nursery owner and Farm Bureau leader Janet Silva Kister testified in Sacramento on the need for continued DRW funding to the Assembly Budget Subcommittee on Resources, and has talked with CFDA Secretary of Agriculture A.G. Kawamura and the governor's budget staff.

“They all agree with us that the Diaprepes root weevil should be eliminated, but the money isn't there,” said Eric Larson, SDCFB executive director. “We know the state is in a fiscal crunch, but that doesn't mean the state can then turn away from its responsibilities. Not spending today to eradicate this pest will lead to untold damage and the massive use of pesticides in order to live with this pest throughout the state.”


For Chuck Badger, eliminated DRW funding could cause the operation to rethink whether growing citrus will be financially viable in the future.

“If the state cuts the funding, we would definitely rethink citrus,” Badger said. “The only problem is with so many hosts for DRW I'm not sure what else we would consider. That's what's so scary about this pest.”

For more information, UC Davis has a DRW brochure on its website at


4 photos


Diaprepes weevil.jpg

Cut-line: THE DIAPREPES root weevil is a serious threat to the nursery, citrus, and other agricultural sectors in California's San Diego County. The area's climate is similar to the weevil's native home in the Caribbean.





Bender, Bates.jpg



CU weevil.jpg

Cut-line: ADULT DIAPREPES root weevils are medium-sized, polymorphic weevils that are three-eighths to three-quarters of an inch in length. The insect always has stripes with colors ranging from orange, yellow, gray, and black.

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