The Asian citrus psyllid is the primary vector of HLB which Osama ElLissy says is ldquothe most devastating disease of citrusrdquo

The Asian citrus psyllid is the primary vector of HLB, which Osama El-Lissy says is “the most devastating disease of citrus.”

USDA/APHIS specialist says — Insect, disease ‘could take out citrus industry’

The phrase ‘Life on the Inside’ sounds like a movie about a convicted felon sentenced to prison without parole. In reality, the phrase represents the new status quo for U.S. citrus nursery growers.

In the real world of citrus nursery production, growing citrus plants in approved protective structures is becoming an economic and regulatory mandate to protect the citrus industry from insidious pests and diseases that threaten its future.

The U.S. citrus industry today employs 110,000 people from Florida to California, with an economic value of $12.3 billion nationally, including wholesalers, retailers, and other industries. About $4.7 billion is generated in annual wages.

The top pest and disease combo that continues to threaten worldwide citrus production is the Asian citrus psyllid (ACP), Diaphorina citri, and the bacterial Huanglongbing disease (HLB), Candidatus Liberibacter asiaticus, also called citrus greening.

The ACP is the primary vector of HLB, but the disease can also be spread through grafting. ACP adults and nymphs carry the bacteria. The insect usually feeds on new plant flush.

Adult psyllids are small 1/8-inch to 1/6-inch brownish insects, similar in size to an aphid. The insect feeds with its head down, almost touching the surface of the leaf.

“HLB is not just one of the most devastating citrus diseases — it is the most devastating disease,” says Osama El-Lissy, director of emergency and domestic programs in the plant protection and quarantine unit with the USDA-Animal and Plant Health Inspection Service (APHIS) in Riverdale, Md.

“HLB will not only impact the industry economically — it will take out the industry,” he says. “There is no cure for HLB. An entire orchard can die in three years. That’s total destruction in a short period of time.”

 A host of pests and diseases, including HLB, citrus canker, citrus black spot, and sweet orange scab, confront the U.S. citrus industry. Florida citrus growers battle all four organisms.

According to El-Lissy, losses to the Florida industry total about $300 million annually from pests and diseases. Growers spend $500 per acre per year in pest control and citrus diseases have increased production costs by 40 percent. The industry has been able to survive these extra costs through higher fruit prices.

HLB-caused tree death is tied to blocking nutrient movement through the phloem, the living tissue that carries organic nutrients to all parts of the plant. The tree is choked and eventually starves to death. HLB symptoms include blotchy leaf mottling, yellowed leaves, and small, misshapen, sour-tasting fruit that is unmarketable.

The three HLB strains include Asian, African, and American. Brazil has the American strain, while the U.S. has the Asian version.

Florida citrus acreage has fallen from about 800,000 acres to 539,000 acres; about 120,000 acres have been abandoned due to pests and diseases, El-Lissy says.

Florida grows citrus mostly for juice. California is the nation’s second largest citrus-producing state, with 253,000 acres, followed by Texas, with 27,000 acres and Arizona, with 22,000. California fruit is sold mostly for fresh consumption.

Texas, Mississippi, and Alabama have detected the ACP, but not HLB. Florida, Georgia, South Carolina, and Louisiana have both.

HLB was first discovered in China in the early 1900s. El-Lissy drew a troubling road map of the rapid spread of the ACP and HLB worldwide. The disease was confirmed in Brazil in 2004, and the first U.S. find was in Florida in 2005. Over the past two years, it has been found in Central America, other southern U.S. locations, and in a handful of places in Mexico. Each HLB find in Mexico has been closer to the U.S.

“You can see a trend, and it’s headed this way,” El-Lissy says. “The situation in Mexico is quite troubling. Some citrus growers there are considering replacing citrus with sugarcane. The Mexican government is providing financial assistance to help growers with these decisions.”

California citrus industry leaders state verbally it is not a matter of if, but when, HLB is found in the Golden State.

The ACP was first found in California in the fall of 2008 in San Diego County near the U.S.-Mexico border. The pest moved to the counties north and west. Quarantines for the pest, or situations related to the pest, involve Imperial, Los Angeles, Santa Barbara, Riverside, Orange, and San Bernardino counties.

All California ACP finds have tested negative for HLB. The insect has not been found in the Central Valley, a major citrus production area.

The ACP has been intercepted in packages coming into California containing fruit and plants, including citrus, ornamentals, herbs, and cut flower bouquets shipped from other states and countries.

Federal and/or state ACP quarantines are in effect for the entire states of Texas, Louisiana, Mississippi, Alabama, and Hawaii, plus portions of California, Arizona, and South Carolina. Quarantines for ACP and HLB are in place in the entire states of Florida and Georgia, plus Puerto Rico.

California’s citrus industry is benefitting from the ACP-HLB lessons learned the hard way by other states and countries. Citrus leaders are actively engaged in planning and pooling financial resources to fight the threat.

“We have to partner,” El-Lissy said. “We must have a solid way to coordinate, communicate, leverage resources, and pull everything together to handle the disease in the most effective and practical manner. Everyone is pooling resources to move us forward to deal with the disease.”

Nationwide, the short-term strategy is to slow the spread of ACP and HLB from infested areas to healthy areas, and to suppress the ACP.

California’s offensive includes routine inspections of 47,000 yellow panel sticky traps, 6,000 visual tree inspections, and testing 15,000 plant tissue samples. Traps are placed in a project area at a density of 100 traps in the core and 50 traps per square mile in the surrounding eight square miles of an ACP find.

Within 400 meters of an ACP find, citrus trees and host plants are treated with a foliar application of the insecticide Tempo, which kills the ACP. The host tree or plant is also soil-drenched with the systemic insecticide Merit to protect against psyllids over an extended period.

El-Lissy says the protection of foundation citrus nursery stock is critical for the long-term health and survival of the citrus industry. Part of the solution is a clean nursery stock network.

“The citrus nursery stock sector is the foundation of which the citrus industry is based,” he says. “If the nursery

El-Lissy says the protection of foundation citrus nursery stock is critical for the long-term health and survival of the citrus industry. Part of the solution is a clean nursery stock network.

“The citrus nursery stock sector is the foundation of which the citrus industry is based,” he says. “If the nursery stock system gets HLB, then you lose the whole system. We need rules in place that are effective, efficient, but yet practical, in order to safeguard the nursery stock system.”

APHIS regulations will require U.S. citrus nursery stock production in a pest-exclusion area screen house designed to prevent pest and disease penetration. The screen size must be 0.3 square millimeters or less in size. Each protective screen facility will be inspected.

El-Lissy says the long-term solution to HLB will involve a national coordination of research aimed in part at breeding HLB-resistant plant cultivars.

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