The Herald (Brownsville)
Posted: Tuesday, November 3, 2015 10:28 pm
Nearly 70 years after it was eradicated in South Texas , traces of citrus canker have been confirmed in Rancho Viejo.
Survey teams of about 40 personnel from the U.S. Department of Agriculture, Texas Department of Agriculture, Texas A&M Citrus Research Center and an industry group, Texas Citrus Pests and Disease Management Corporation, began going door to door the week of Oct. 26 in search of infected trees.
Suspected citrus canker, a bacterial disease extremely destructive to citrus crops, was discovered on a lime tree at a Rancho Viejo residence on Oct. 16, according to Yindra Dixon of the USDA Animal and Plant Health Inspection Service.
A sample of the tree was sent to the TAMU Citrus Research Center and the USDA APHIS Plant Protection and Quarantine Program, and citrus canker was confirmed on Oct. 23, Dixon said.
The first step was to establish an initial “delimiting area” in a one-mile radius from the infected area, she said. Within that area, surveyors are inspecting as many citrus trees as possible to find out several things, among them how long the disease has been in the area, Dixon said.
Citrus canker can be spread by high winds and rain, neither of which has been in short supply in the Rio Grande Valley recently. The disease causes deformed, inedible fruit in addition to spots, scabs and defoliation, she said.
Citrus canker was introduced to the southern United States early in the last century and was eradicated in Texas in the late 1940s, she said.
“You guys haven’t seen it in over 50 years,” Dixon said. “That’s why we want to contain it as quickly as possible.”
George Nash, in charge of the inspection as emergency coordinator with the APHIS protection and quarantine unit, said the teams’ canvass of approximately 1,000 Rancho Viejo properties is about 75 percent complete.
Of the 22 samples analyzed so far only five have tested positive for citrus canker — all of them from lime trees, he said. The hope is that the Rancho Viejo is the lime-specific “W” strain rather than the “A” canker strain, which attacks virtually all types of citrus, Nash said.
The APHIS Center for Plant Health Technology will make that determination, though it could take two or three to weeks to get an answer, he said.
“That would be a lot easier for everyone if it’s just limes,” Nash said.
The CPHT will also do a scientific analysis of wind and rain patterns and topography to get an idea of where the disease could have spread and thus where to look next, he said. Nash thinks a quarantine is likely, though that decision will come from higher up, he said.
The delimiting zone could be expanded up to five miles, though that too will depend on what APHIS recommends, Nash said.
The last thing the Valley needs is another citrus disease. Growers and scientists were already battling citrus greening, or Huanglongbing , a serious, insect-borne disease wreaking havoc on the U.S. citrus industry.
Nash’s office is the lead surveyor on that disease as well and has set up 10,000 “sentinel sites” at residential properties across the Valley. APHIS confirmed the first case of greening in Texas at one of those sites, in San Juan , in January 2012. No cure has been found for the disease.
As for citrus canker, no one knows how it made its way to Rancho Viejo, though the disease is not known to occur in Mexico , Nash said.
“We’re still looking into how it got introduced,” he said. “With plant pathogens that will take a while.”