Three Western citrus nurserymen support the construction of insect-proof protective structures to protect plant stock from possible future infestations of the Asian citrus psyllid and its vectored disease, citrus greening.

Whether all nurserymen can financially afford the structures is a concern.

Protective structures could become mandatory for California citrus nurserymen. State Senate Bill 140, the Citrus Nursery Stock Pest Cleanliness Program, would give the California Department of Food and Agriculture the power to prescribe standards of cleanliness for nursery stock.

A proposed regulation could require that all mother plants be kept in insect-proof protective structures by 2012, and increase trees be placed under structures by 2013.

The Asian citrus psyllid (ACP) was found in California’s San Diego and Imperial counties last year. While citrus greening (Huanglongbing disease, HLB) has not been detected in California, the ACP typically spreads HLB. The disease causes certain tree death and ruins the citrus. Neither has been found in Arizona.

The pest and disease have devastated Florida’s citrus industry. Nurserymen in Florida, Spain, and Brazil have instituted mandatory insect-proof houses to keep the psyllid and HLB out.

The Dillon family of Fremont, Calif., is well aware of the perils of citrus pests and diseases. Floyd Dillon launched Four Winds Nursery in Ventura County in the 1950s; an operation he later moved to Fremont to avoid a quarantine tied to citrus tristeza virus.

Today grandson Don Dillon, vice president, operates the 22-acre wholesale citrus nursery. Sixteen additional acres are located in Winters, managed by Dillon’s sister Mary Ellen Seeger and husband John Seeger.

The family sells 50 varieties of citrus for retail valued at about $5.5 million annually.

“We’ve always been concerned about disease issues and have supported certification programs to keep nursery stock clean; whether for commercial or retail use,” Dillon said.

Dillon is keenly aware of the ACP and HLB issue. Experts predict it is just a matter of time before the insect heads north to the large commercial citrus growing region in the Central Valley where about 75 percent of California’s commercial groves are located.

“The regulation on mandatory protective structures is up in the air,” Dillon said. “We’re being told that if an insect lands in our nursery then our nursery stock might be put on indefinite hold even in the absence of the HLB bacteria. There would be no compensation for inventory which would put you out of business. It is a concern.”

Dillon supports building insect-proof structures to keep ACP and HLB out of nurseries, but is wary of the high costs. He says a regulation should be mandatory for all nurserymen to keep them on the same level playing field and keep all plants healthy.

“At the end of the day I would support a mandatory program,” Dillon said. “I think that’s the smartest thing to do. It’s easy to say that we have basic support for a mandatory program. To actually go to the large expense to purchase insect-proof structures is very intimidating.”

Recommended insect-proof protective structures include screenhouses featuring screen mesh and greenhouses constructed of hard plastic or glass. Dillon is unsure which option he might adapt. Dillon does not currently have an insect-proof structure.

Could Dillon financially survive a large capital outlay?

“We ask ourselves that question everyday,” Dillon said. “Once we learn more about what type of structures we would have, we would pencil it out to see where we stand. At the end of the day I would need to recoup some of the increased costs through higher prices for the trees I sell.”

Dillon said a new structure in the $10 per-square-foot range could total about $400,000 for a one-acre structure.

“The biggest challenge I would face is whether to continue growing larger-sized trees in an indoor environment. That could be very expensive,” Dillon said. “We would have to re-evaluate our entire operation and what sized trees we would grow.”

Dillon, as well as other Western nurserymen and industry leaders, attended an ACP-HLB workshop in Riverside, Calif., in June, where protective structures were discussed.

Mark and Stacey Loghry, fourth generation citrus nurserymen, own and operate Sunset Nursery in Yuma, Ariz. Most of their 5- and 15-gallon, and 24-inch nursery stock is sold to independent retailers. Some lemon and Minneola trees are sold to commercial growers.

The Loghrys are further ahead than many Western nurseries in adapting to insect-free structures. The Loghrys last year converted an open flat-shade structure to an enclosed, flat-screen structure to house the nursery’s finishing operation.

The Loghrys recently took delivery of an arch screenhouse from AgraTech, a greenhouse manufacturer in Pittsburg, Calif. The structure will serve as the propagation and seed house. A 4-foot polycarbonate stem wall will be installed at the ground level with the remainder of the walls and the roof made of screen.

“Temperatures in Yuma can reach 120 degrees during the summer,” Mark said. “The screen roof will allow the heat to escape through the roof instead of held inside.”

A soft-plastic liner can be rolled over the roof and the walls during the winter months to maximize heat use. The Loghrys are using 50-by-25-size mesh in the screenhouses, the standard size used in many Florida protective structures. A protective structure for the source (mother) trees will be the family’s next purchase.

The Loghrys predict the new structures will increase growing costs by about 40 percent. The structures could create efficiencies that might offset a portion of the increase. Part of the higher costs would be passed on to customers.

Mark said, “When you’re looking at higher production costs then you have to consider growing some smaller trees to sell instead of all larger trees.”

“A smaller, less expensive tree might be more appealing to some consumers,” Stacey added. “We will expand our size options, but we’re hopeful our customers will continue to purchase larger trees. We’re banking on it.”

Sunset Nursery will be one of a few growers of 24-inch citrus trees in the West.

The Loghrys support a mandatory requirement for protective structures for all Western citrus nurseries.

Fourth-generation citrus nurseryman Steve Maddock owns and operates Maddock Nursery in Fallbrook, Calif., near the San Diego-Riverside county line just off Interstate 15. The citrus and avocado nursery grows nursery stock mostly for commercial growers, plus some trees for retail and landscaping.

Maddock is uncertain about his future as a nurseryman with or without the ACP and HLB issue. Wildfires destroyed much of the nursery in October 2007. The financial loss totaled several million dollars.

“We’re still picking up the pieces,” Maddock said. “We want to continue in the citrus nursery business.”

The enormous loss has left the family uncertain on whether they could afford insect-proof structures.

“We’re not sure if we’re in a position to make these upgrades for the new growing protocol,” Maddock said. “Hopefully we could ease into it in stages; if not we may have to walk away from it. We’re real thankful for the years we had.”

Maddock already has his budwood operation located inside a greenhouse.

Maddock is concerned about other threatening factors. The available water for the nursery from the Metropolitan Water District was reduced by about 40 percent last year. Supplemental groundwater is very salty and a reverse osmosis system to remove the saline is costly.

Maddock’s son, John, who also attended the workshop, hopes to continue the family legacy; a future that’s still to be determined.

email: cblake@farmpress.com