Citrus Greening Disease, or Huanglongbing (HLB), is a serious threat to the commercial citrus industry. Just ask Florida citrus producers who suffered a devastating blow when the disease was first detected there in 2005. Since then, the state’s citrus acreage has declined from 748,555 acres in 2004 to 531,493 acres in 2012, a 28 percent loss.
To date, the Florida citrus industry has invested $66 million in 129 research projects run by 30 doctoral scientists looking for a solution to the disease. Still, the Asian Citrus Psyllid (ACP), the moth credited with infecting citrus trees with the disease, is still present in Florida, and the flying culprit is spreading.
The moth -- and the disease -- has since been discovered in citrus trees inGeorgia, South Carolina, Louisiana, Texas, and most recently, California.
It has been just over a year since HLB was discovered in a commercial citrus grove in the fruit-rich Rio Grande Valley of Texas. Almost immediately quarantine was established in the Valley to help prevent the disease from spreading, and that quarantine remains in effect today.
While early detection of ACP in the Valley is being credited with helping to greatly contain the disease, a comprehensive management plan continues, with Valley growers and state and federal authorities spending hundreds of thousands of dollars in an attempt to keep the problem in check and in search of a better way to stamp out the problem. While the expensive fight against HLB is helping to save the Texas citrus industry, no one is lowering their guard.
“The outbreak of citrus greening in Florida and the resulting damage to the citrus industry there served as a wake up call to other citrus producing areas including Texas, California and Arizona,” said USDA tropical researcher Dr. Robert Mangan, former acting director of the now-closed Kika de la Garza Subtropical Research Center in Weslaco. “Until science can develop a better defense against the disease, control and management of infected areas remain a concern.”
Indeed, control and management of the psyllid that carries the disease -- and the disease itself -- is problematic. Fighting HLB involves constant monitoring of psyllid movement including specially designed traps. When psyllids are found in traps in a new area, a system of spraying of adjacent citrus groves is performed to eradicate them, and this adds considerably to the input costs producers must bear in order to produce healthy fruit.
Fortunately the disease is not spread by the fruit, but can be spread from transporting citrus tree cuttings or leafy material to uninfected areas. As a result, plant nurseries within and near quarantine zone are prohibited from shipping citrus plants.
But state and federal quarantines and grower management and control may not be enough to contain the problem. Officials are now enlisting the aid of homeowners in the Valley and up the sub-tropical coastline of Texas to join in the fight against ACP and greening disease.
In a press release last week, Texas A&M AgriLife Extension Service horticulturist Barbara Storz in Edinburg said last week that all commercial citrus trees in the Valley infected with HLB have been destroyed to prevent spread of the disease, but the Asian psyllid can still be found in all corners of the Valley.
“Twenty one citrus psyllids, the insects that transmit the disease from tree to tree, have tested positive for citrus greening. These ‘hot’ psyllids have been found from one end of the Valley to the other, from Brownsville to Mission. What we don’t know is where these psyllids are picking up the disease,” she reports.
Storz said the psyllids could be picking up the disease anywhere, from infected trees across the border in Mexico to residential backyards where homeowners maintain “ornamental citrus trees”. These trees are generally not monitored for psyllid movement, and that could be problematic.
In November, Texas AgriLife officials in the Coastal Bend warned homeowners to be on watch for signs of HLB in ornamental citrus trees, which can be found in large numbers in Corpus Christi. Now officials in the Valley are once again encouraging homeowners to become more aware of their citrus trees.
“There are lots of efforts to manage this pest in commercial orchards, but we need homeowners involved,” she said. “Psyllids are especially attracted to flushes, or new tree growth. Since trees are flushing right now, this is a perfect time for homeowners to treat their trees. Which insecticides to use and how to use them will be discussed at the March 7 meeting.” Storz said.
That meeting is scheduled at the San Juan Memorial Library, 1010 S. Standard St beginning at 6 p.m. Sponsors of the meeting include AgriLife Extension, the City of San Juan, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service, the Texas Department of Agriculture, Texas A&M University-Kingsville and Texas Citrus Mutual.
More information about psyllid control can be found online at http://hidalgo.agrilife.org . Click on the Gardening tab. For more information on the meeting or citrus greening call 956-383-1026.