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20130705 ACP-adults-laying-eggs featureMISSION—According to USDA Animal and Plant Health Inspection Service citrus greening is one of the most serious citrus plant diseases in the world. Once a tree is infected, there is no cure.

Until recently, this critical citrus disease that kills the tree itself, was found in Florida and California, but not the Rio Grande Valley. That changed a year and a half ago when, in January 2012, citrus greening disease was found in two groves in San Juan, according to Texas Citrus Mutual President Ray Prewett.

A New York Times article published last month states USDA (United States Department of Agriculture) crop estimates for Florida’s citrus production this year have been downgraded for five consecutive months, ascribing most of the losses to greening disease. Greening was first detected in Florida in 2005 and has spread to all 32 citrus-growing counties throughout the state, devastating the citrus industry. Florida citrus growers have vigorously tried to combat the disease, spending over $60 million on research trying to eradicate greening. But no solutions have been found.

The disease could completely wipe out the $9 billion citrus industry in Florida if a solution is not found soon.

Huanglongbing (HLB), or citrus greening, is not dangerous to humans or animals, but the fruit produced by an infected tree is not useable, depending at the stage of the disease. After a period of a few years with infection, the tree will eventually die.

Citrus greening is transported by a tiny insect – the Asian citrus psyllid – and is responsible for ruined citrus crops through much of the United States, including Florida and California.

20130705 ACP-InfoBox“It is a work in progress. We are close to getting all the infected trees removed,” Prewett said. “We know this is a long term challenge.”

Prewett added some residential homes in the general vicinity were infected as well. Groves that are infected are immediately placed under quarantine, as well as groves within a five-mile radius.

Rio Grande Valley growers hope to slow the disease, but unfortunately, their efforts are delayed by abandoned groves and groves that are not treated for psyllids.

“We are concerned that we have groves out there that have been bought for development and are not being cared for. There tends to be higher levels of psyllids in those groves,” Prewett said. “Over the next several months there will be a lot more public outreach. The growers are stepping up and getting more involved.”

New technology is being developed to assist in the search for infected trees. Prewett said Texas A&M University-Kingsville Citrus Center in Weslaco is researching the disease. He said growers are also trying to learn from Florida and other areas that have been devastated by the disease.

Prewett explained that $60 million has been spent in Florida in research alone, but no cure has been found to for the disease. Dennis Holbrook owner of Mission-based South Tex Organics said research is moving forward with everything from genetically modified trees to technology.

A machine is being developed to assist growers in sniffing out the greening disease, according to Holbrook. The advanced technology has been 100 percent accurate in the testing process for spotting greening disease.

Other advances include something that resembles a DNA test for humans to determine whether a tree is affected by greening. Holbrook said this test is still in the trial process and is being developed by a company in Austin, but has not been approved by USDA.

Multiple avenues are being researched to assist in the early detection of diseases in fruit, but Holbrook said recent research shows once the disease hits the foliage it goes to the root system before it reemerges.

“There is a latency issue; it takes two to four years before it shows indication of the disease,” Holbrook said. “That leaves a place for another insect to feed off that tree and deposit into another tree. If we have early detection you reduce transmission.”

Holbrook said currently the only real option is to bulldoze the orchards that contain the disease, and basically start over.

“Florida has thousands of acres that have been abandoned or infected” by greening disease, said Holbrook. “In Florida, the fruit has been half green and half orange, the fruit never completely matures,” he said. “That part is just thrown away, it can’t be used for any purpose. Here in Texas, we don’t have fruit in that condition.”

20130705 ACP-DSC 0006Even after a tree contracts the disease, some fruit is still edible. Owners of the few citrus groves quarantined in San Juan were able to save the unaffected fruit.

“The thing about greening, even though the tree is infected, the remaining or surrounding fruit can be utilized,” Holbrook said. But precautions have to be taken.

The quarantine process allows growers to harvest the edible fruit, but leave any portions of the plant and fruit that is affected by the disease. Holbrook said the fruit has to be sprayed prior to harvesting to prevent spreading the psyllid to other areas.

“The fruit has to be clean of any twigs and leaves, and once placed in the truck for transportation it has to be covered and protected,” Holbrook said. Once the fruit is taken to the packaging shed it has to be segregated until it runs through packaging. “Anything that may have slipped by is collected, double bagged and taken back to the grove,” he said.

According to Holbrook, fruit that has been taken by greening disease basically does not mature and stays sour. He added, the plants infected in the Rio Grande Valley have been removed, which is why growers don’t see fruit in the advanced greening process. But psyllids in the area have been shown to be carrying the disease.

“There could be potentially other sites that show up within a time frame. We are just kind of watching and waiting. We encourage people who are not spraying for psyllids to spray, because they are putting the rest of the industry at risk.”

For more information on how to check if citrus plants show signs of the disease, visit the Texas Citrus Mutual website at and USDA’s website

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