The emergence of farmers markets in the Lower Rio Grande Valley has led to new research that shows planting dates affect the productivity of organic tomatoes, according to an expert at the Texas A&M AgriLife Research and Extension Center at Weslaco.
"Just a few years ago, between Brownsville and Rio Grande City, there were no farmers markets anywhere," says Dr. Raul Villanueva, an AgriLife Extension entomologist.
"Now, there are seven or eight that are doing very well. The demand for fresh, locally grown fruits and vegetables is obviously high and growing, especially for organic produce."
But growing fruits and vegetables in the subtropical climate of South Texas without the use of synthetic pesticides is a real challenge, especially when it comes to tomatoes, Villanueva says.
"People who grow produce for farmers markets here have become quite successful in going organic, but they were really having problems with tomatoes," he says. "That's due to a virus spread by whiteflies that severely limits production. It's called yellow leaf curl virus.
"In fact, that virus, coupled with competition from Mexico, is why tomatoes are not grown here commercially like they were back in the 1950s and 60s. There are some tomatoes still grown here for canning, but the acreage is very small, about 200 acres."
The virus debilitates the plant, causes plant leaves to curl upward along the edges, and can knock tomato production to zero, Villanueva says. Whiteflies are abundant because they feed on other crops including cotton, corn, watermelon, and others, creating continuous populations that feed on and transmit viruses to tomatoes, watermelons, and potatoes.