Research

by Rod Santa Ana, Texas A&M AgriLife Communications

WESLACO – It’s an imaginary toolbox, but Dr. Ismael E. Badillo-Vargas wants to create one for South Texas growers to help them revive what was once a thriving vegetable industry in the Rio Grande Valley.

It would contain both short- and long-term strategies to once again harvest vast fields of produce in Texas for local, national and international markets.

Badillo-Vargas, a Texas A&M AgriLife Research insect vector entomologist in Weslaco, said insects and the plant diseases they carry represent a formidable barrier to farming lucrative vegetable crops.

After decades of being a top producer of vegetables in the country, Texas is now a net importer, according to U.S. Department of Agriculture statistics.

“Insects, especially those that are vectors of plant pathogens, pose a new challenge for vegetable production in Texas,” he said. “Those insects were not here in the 1950s, ‘60s and ‘70s. Insects presently in the Rio Grande Valley are constantly changing, and they are carried here not only by changing weather patterns that can disseminate them long distances but also by human and commercial traffic to and from the area that didn’t exist back then.”

Badillo-Vargas said Trojan horse-type insects, those that arrive carrying pathogens, pose a double whammy to an area.

“Suddenly, an area like the Valley doesn’t have just a new insect pest to deal with, it also has a new plant disease never seen here before,” he said. “It takes a great deal of research to learn the biology of that new insect as well as how the disease works. And sometimes, the pathogen can change the insect or vice-versa. It can get very complicated.”

Unlike areas that routinely have hard winter freezes, the subtropical climate of South Texas allows insects and pathogens to survive year round, moving among host plants as the seasons change.

“In the absence of crops, after a harvest, for example, an insect population can move to weeds in ditches to survive,” he said. “Once crops are planted again, they simply move from the weeds back onto the crops. The pathogens they carry also survive.”

Those pathogens can be bacteria, fungi or viruses, which require different approaches to control, Badillo-Vargas said.

“And different insect vectors carrying any of these pathogens will also require multiple strategies to control their damaging effects.”

Insecticides can be effective, but because insects have an innate ability to adapt, they can quickly develop resistance to those insecticides.

“Suddenly, an insecticide that was highly effective against an insect is no longer effective, so it’s important to develop insecticide rotation programs,” he said. “That helps.”

An insecticide rotation program would occupy the short-term strategy segment of the tool box, along with cultural and biological control practices.

“Cultural practices would include recommendations on farming methods,” he said. “This could include recommended planting dates or using different types of mulches. Biological control would involve the use of ‘good’ insects controlling the populations of ‘bad’ insects. That’s our goal, to develop new strategies that could be combined into an integrated pest management program to make it more difficult for pests and pathogens to succeed.”

Long-term strategies in the toolbox will first require gaining an in-depth understanding of the interactions of vectors and the pathogens they transmit to develop resistant varieties and transgenic plants genetically modified to resist pests and diseases, Badillo-Vargas said.

“One example of this is what’s called RNAi, or RNA interference,” he said. “These studies take much longer to develop, but basically involve targeting a gene in the insect’s genetic makeup that plays a key role in reproduction and/or the ability to transmit a pathogen.

“If we can switch off that particular gene, the insect would not be able to reproduce, or it wouldn’t have the ability to infect plants with the bacteria or virus it’s carrying.”

A combination of short- and long-term weapons in the toolbox could allow vegetable growers to produce healthy, profitable crops once again, Badillo-Vargas said.

“But it takes time, even after you’ve developed a new strategy, to determine scientifically that the strategy is effective,” he said. “It takes several seasons of testing to make sure that success in the first, second or third season wasn’t just a fluke.”

And during all this time, weather patterns and insects keep changing, and commerce and travelers continue introducing new challenges to an area.

“All of these studies take time and a tremendous amount of resources, but Texas A&M AgriLife is determined to make the investment required to revive the state’s vegetable industry,” he said.

A native of Puerto Rico, Badillo-Vargas assumed his duties in February at the Texas A&M AgriLife Research and Extension Center at Weslaco. Among his first steps to help growers was to set up a large research field plot of tomatoes and potatoes to monitor the insects currently in play.

“We haven’t found anything we weren’t expecting,” Badillo-Vargas said. “In tomatoes we’ve encountered whiteflies, red mites and thrips. In potatoes, of course, we have the potato psyllid that transmits zebra chip disease. And there are major and minor aphids affecting both crops, and some insects that can move to other crops, like whiteflies in cotton.”

Badillo-Vargas’ colleagues and collaborators at the Weslaco center include Dr. Carlos Avila, an AgriLife Research vegetable breeder, and Dr. Juan Anciso, the Texas A&M AgriLife Extension Service fruit and vegetable specialist, among others.

Badillo-Vargas also administers a statewide program that tracks migration and population patterns of the potato psyllid.

“Stakeholders throughout the state of Texas, the nation and even other countries subscribe to our findings because it’s such an insidious vector of zebra chip disease in potatoes,” he said. “Many growers and other stakeholders want to know what they’re up to and where. They use this information to best combat this insect vector and bacterial pathogen in potato growing areas.”

Badillo-Vargas said it is difficult to predict but short-term strategies to help Texas growers begin producing profitable vegetable crops could be possible in five years. The long-term strategies that involve in-depth understanding and genetic work would likely take longer.