A bacterial disease that has infected 75% of Florida's citrus trees and made inroads in California — ruining fruits' shapes and flavors and ultimately killing the trees — has a stronghold in the Rio Grande Valley.
Known as citrus greening, it first appeared two years ago with a handful of infected trees in the border city of San Juan but is now showing in alarming numbers, mostly in a "hot zone" in the mid-Valley.
So far, the disease has only been found in one residential tree in the Hacienda Heights area of Southern California. But the psyllids have spread throughout the region, and a massive quarantine prohibits the movement of citrus fruit and trees out of the area.
Despite the regulatory net, the bug has hitchhiked its way to the central San Joaquin Valley, having been caught in insect traps in Fresno and Tulare counties. To keep the psyllid in check, farmers have sprayed their groves and the state has treated residential trees where the psyllids have been caught.
A quarantine also has been put in place that covers 870 square miles of the central Valley's citrus belt.
Texas Citrus Mutual, a growers' trade group, said the disease had been detected in 430 trees in commercial groves and 207 in residential backyards as of last week. More than 100 of the infected trees were found in La Blanca , an unincorporated community north of Donna.
Hundreds more were found in orchards and a former nursery to the south.
"The question weighing heavily on the minds of growers and many others in south Texas is whether Texas can avoid a catastrophic situation for our citrus industry, which wasn't the case for our eastern neighbors in Florida," Texas Citrus Mutual President Ray Prewett said.
The disease's latency period makes it difficult to know how long a tree had been infected, he said.
"Trees will have the disease in a lot of cases for at least two years before they show symptoms," he said. "If they don't show symptoms, you can't fully even run tests."
Also known as huanglongbing, or yellow dragon disease, citrus greening causes misshapen, off-tasting, green-tinted fruit and ultimately kills trees. It is carried by the Asian citrus psyllid, a type of jumping lice that originated in Asia and made its way to the Western Hemisphere.
While Texas' citrus industry is tiny compared with Florida's, the Rio Grand Valley's sweet oranges and trademark red-fleshed grapefruit have an annual local economic effect of $150 million.
Both growers and scientists say Texas has, unlike Florida, been able to take preemptive steps against the disease, and Congress and the U.S. Department of Agriculture have allocated millions of dollars for research into methods to stop its spread. The industry has funded a Spanish- and English-language awareness campaign.
"They've been detected at a reasonably early stage (in Texas). It might be two years after infection, but it still hasn't spread through the whole tree," said John da Graca, director of the Citrus Center at Texas A&M University-Kingsville.
At present, all of Hidalgo and Cameron counties are under quarantine, and the USDA is continuing "door to door" testing.
Trees with the disease also were found recently in nurseries in Webster, south of Houston. That prompted a third quarantine, in Harris County.
The industry is offering tree removal services for homeowners and encouraging commercial growers to likewise destroy infected trees.
Texas growers hope to avoid the kind of devastation Florida has experienced.
"They wish they were where Texas is, where removing trees would make a difference," Prewett said. "They got to the point where 70% to 80% of their trees are infected. Well, you can't take out 70% to 80% of your trees and have any of your industry left."
Periodic testing of trees in cities including San Antonio and Corpus Christi so far hasn't found signs of citrus greening.
"It is simply too early to know how the situation will unfold," Prewett said. "However, we know that all Texans, from commercial growers to nursery owners to homeowners, must continue to be aggressive to slow the spread of the disease."
He said the industry was for the first time planning a strategic "spray surge" in September, a typically wet month that is prime spawning time for the disease-carrying psyllid.