Texans asked to help keep citrus canker in check

By Rod Santa Ana, Texas A&M AgriLife

After finding citrus canker in the Lower Rio Grande Valley, experts want the public to know the facts of the disease because they can play a big role in limiting its damage.

Dr. Olufemi Alabi, a Texas A&M AgriLife Extension Service plant pathologist in Weslaco, said the first thing the public should know is fruit from a tree with citrus canker is safe to eat.

“Citrus canker creates lesions on the stems, leaves and eventually the fruit of citrus trees,” he said. “The fruit is still edible. The blemishes do not affect the internal quality of the fruit, but they do reduce its commercial, fresh fruit marketability.”

Citrus canker is a bacterial disease discovered in October on lime trees at a residential area in Rancho Viejo, a small community near Brownsville.

The disease is not new to the area or the U.S., having caused major losses in citrus production in Florida and other areas for years. Brazil is also struggling with citrus canker.

A one-mile delimiting area has been established around the positive site at Rancho Viejo to allow surveyors to determine how widespread the disease has become, Alabi said. The area is not quarantined, but is mapped for intensive surveying.

“Scientists from the U.S. Department of Agriculture’s APHIS, or Animal Plant Health Inspection Service, in partnership with local scientists and the citrus industry, are scouting for other infected trees, and they are trying to determine the strain of citrus canker we’re dealing with,” he said.

There are several strains that differ greatly in their host range and severity, he said.

“Hopefully, we’re dealing with a strain that is not as virulent as Strain A, which is a very potent strain. And there’s a strain that affects only limes. I’m optimistic that what we have is not a serious strain, and this will not be a serious problem here.”

Citrus canker is especially threatening to the Lower Rio Grande Valley because its citrus industry produces fruit largely for fresh fruit market sales. Most of Florida’s citrus goes to juice.

“Even though the fruit is safe to eat, consumers shy away from fruit that is blemished, so we’re hoping we had a small outbreak of this disease and that it is of a weaker strain.”

Alabi said comparisons cannot be made between the citrus canker devastation in Florida and the find in South Texas, for now.

“Citrus canker has been around for ages,” he said. “In fact, it was reported in the Kingsville area back in the 1940s. It was said to have been eradicated and until now, there had been no other reports of it in Texas.

“But we have to remember that plant diseases are influenced by environmental factors. We cannot expect diseases to behave here as they do in Florida or in any other citrus producing area,” Alabi said.

There is no effective cure for citrus canker, Alabi said. While some growers have been known to treat their trees with copper, the substance is toxic to trees with constant usage.

Regardless of the strain of citrus canker detected near Brownsville, scientists are treating the area like a crime scene, careful to not disturb the area in such a way that would promote the spread of the disease.

“Human activity is usually the major culprit in the spread of plant diseases,” Alabi said. “We often introduce a new disease to an area by moving infected trees or plant material. In the case of canker, human activity is a real threat, because the disease spreads via bacterial lesions that can be carried by the wind and rain or on a person.”

It’s possible to inadvertently carry canker bacteria cells on one’s hands, clothes or vehicles, including farming implements, pickups and cars.

“It’s important that if you live within the one-mile delimiting radius that you decontaminate yourself after leaving a site with infected trees,” he said. “Washing hands, clothes and vehicles with disinfectants is advised.”

To prevent the spread of canker in Florida, Alabi said “canker washes” are common where vehicles drive thru a fine mist of a weak bleach solution for decontamination.

The good news is that no new cases of canker have been found in the almost 70 acres of commercial citrus orchards within a five-mile radius of the Brownsville site where canker was discovered, he said.

“The canker was discovered by APHIS employees who have routinely been scouting Valley citrus trees for years,” Alabi said. “And growers have assured us that they are willing to do whatever is necessary to contain the disease.”

Dr. Juan Landivar, director of the Texas A&M AgriLife Research and Extension Center at Weslaco, said cooperation from the public is critical.

“We know we can always count on growers to take the necessary measures to manage plant diseases, but because so many citrus trees are on private property, it is important that the public gets informed and involved in helping to keep the Valley’s famous citrus industry healthy,” he said

Alabi urged the public to call the appropriate agricultural authority if they suspect a citrus tree has citrus canker.

“Don’t take samples,” he said. “Just call and someone will be out to check on the tree. Not all lesions on leaves or fruit mean that the tree has citrus canker. Insect damage, for example, can cause lesions. But to be on the safe side, call in an expert.”

It is also important that homeowners cooperate with surveyors by allowing access to trees for inspection, Alabi said.

“We all have a role to play to ensure that we continue to grow superior citrus fruit in the Valley,” he said.

To report suspicious trees, call the Texas Department of Agriculture at 512-463-9885 or the U.S. Department of Agriculture’s APHIS at 956-205-7702 or submit a report online at www.saveourcitrus.org.

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