Citrus growers hear of progress in disease fight
By Kate Campbell
The Asian citrus psyllid can carry a fatal citrus disease. Research focuses on protecting commercial trees from the disease, known as HLB.
Given the number of research developments being reported in the fight to control the Asian citrus psyllid and find a cure for citrus greening, California citrus growers said they had reason for optimism following a briefing this week. The combination of the insect and the disease have devastated commercial citrus groves in Florida and Brazil, as well as in other locations around the world.
From the first sign of a threat to California's $2 billion citrus sector, growers, government agencies and academic researchers teamed up to address the threat. The goal has always been to keep citrus greening—also known as huanglongbing or HLB—out of California, said Robert Leavitt, California Department of Food and Agriculture director of plant health and pest prevention services.
Leavitt provided a situation report to the California Farm Bureau Federation Citrus/Avocado Commodity Advisory Committee, which met in Sacramento. He said 97 percent of residents in ACP quarantine zones have accepted treatment of their backyard citrus trees.
HLB has been detected in a backyard tree in Hacienda Heights, and Leavitt said the bacterial infection is likely in other, nearby citrus trees.
The psyllid was first detected in California in 2008, and its presence has led to quarantines in Imperial, Los Angeles, Orange, Riverside, San Bernardino, San Diego and Ventura counties.
In addition, about 163 square miles in Tulare County became a restricted area in December, to prevent movement of citrus fruit and citrus plants following detections of ACP in the Lindsay/Strathmore and Terra Bella areas. These restrictions, technically, are not considered a quarantine.
And Leavitt said Santa Barbara County has now joined Tulare County as the leading edge in the pest's advance up the state.
"We can suppress this pest, but we cannot eliminate it," Leavitt told members of the committee, which met as part of the CFBF Leaders Conference. "The long-term solution to preventing the spread of HLB is research."
While research continues, Leavitt said, CDFA is putting field coordinators in place to help deploy resources to emerging pest infestations.
"We're also moving to an aggressive bio-control program," he said. "We simply can't spray fast enough (to stay ahead of the pest)."
Insectaries at the University of California, Riverside, and now at California State Polytechnic University, Pomona, are gearing up to breed millions of tiny, parasitic wasps native to Pakistan. Researchers say they're finding the wasps can reduce ACP populations by as much as 80 percent when released in sufficient numbers.
Leslie Leavens-Crowe, a Ventura County farmer who chairs the Farm Bureau advisory committee, said she recently attended an international HLB conference to learn more about worldwide research efforts.
"There are so many different research avenues being explored, it gives me a sense of hope that we will find a cure," she said. "In the meantime, California growers are behind the world in terms of the level of pest infestation and HLB infections. HLB is a threat, but hopefully we'll beat it."
California Citrus Research Board President Ted Batkin told growers that headway had been made in finding mechanisms for early detection of trees infected with HLB, saying, "After five years of work, we're looking at several ways to detect physiologic responses in trees."
They include sensors that take air samples and can identify a tree's early response to HLB infection, providing positive or negative responses within minutes in the field. The equipment is about to go into commercial production for use in citrus groves.
"We are focused on perfecting early disease detection to find infected trees and take them out," Batkin said. "We're currently testing new sensoring technology in citrus groves in Texas," where the pest and disease have been found.
Through research, Batkin said, "We've been trying to use multiple approaches to finding answers. Now, we're connecting and cross connecting our research.
"I'm staking my (professional) life on it," he said. "We will be able to keep this disease out of our commercial groves."
He announced to committee members that he is stepping down from the research board, in order to devote his time to commercial development of electronic and biological technology that can be deployed as quickly as possible to protect citrus trees.
Researchers also are working to develop new pheromone traps to better attract the psyllid and provide improved warning of the pest's presence in groves.
This year, the federal government is putting about $10 million into research efforts, while farmers have been contributing to research costs through a 9-cent assessment on each box of oranges, lemons and other citrus fruit. The assessment has contributed about $15 million to research activities.
"That means we have to engineer resistance," he said, noting that Florida researchers are developing and working with federal regulators to gain approval for newly developed citrus stock.
"The only way to beat HLB is through research and from that standpoint, I'm actually encouraged," Santa Barbara County citrus grower Ken Doty said. "We knew the pest was coming our way and, by slowing the spread, we got more time to research and prepare. We've had a lot of experience with exotic pests and we're better prepared today than five years ago."
Batkin said researchers continue to look for disease-resistant citrus rootstock but so far, naturally resistant plants have not been found.
San Diego County citrus grower Wohlford Burnet said he also found the research update encouraging, because of how fast scientists and government officials have moved to address the problem and worked to develop technology intended to prevent future damage.
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(Kate Campbell is an assistant editor of Ag Alert. She may be contacted at firstname.lastname@example.org.)
Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.