Significant diseases cropping up in cabbage, onions, potatoes
EDINBURG — Lower Rio Grande Valley growers looking for long spells of hot, dry weather may be in for a disappointment, at least through May, according to weather and crop experts.
Barry Goldsmith, warning coordination meteorologist at the National Weather Service in Brownsville, said that while South Texas is now into the drier part of the year, unsettled weather could move across the area periodically for the next two, possibly three, months.
“Because of the time of year, we’re not going to see days of cool, damp, drizzly weather like we had in the winter, but every four to 10 days or so we could see unsettled weather with heavy rainfall,” he said.
Soggy fields have already caused problems this year for Valley farmers who haven’t been able to plant cotton and sugarcane in the quantities they’d like or harvest sugarcane and vegetables in a timely manner, according to experts at the Texas A&M AgriLife Extension Service.
Especially hard hit have been winter cabbage and onion crops, according to Dr. Juan Anciso, an AgriLife Extension fruit and vegetable specialist in Weslaco. Outbreaks of potato late blight have also been reported in several locations across the Valley.
“I’ve never seen anything like this,” Anciso said. “This has been by far the worst season for cabbage and all plants related to it, the brassica group. Preliminary investigations show that they are all suffering from black rot, which is caused by bacteria that thrives in cool, wet weather. ”
Anciso said he sent various samples of diseased plants to Dr. Olufemi Alabi, an AgriLife Extension plant pathologist in Weslaco, expecting Alabi to find various sources for the disease.
“So far, Dr. Alabi has found just one cause, the bacteria that causes black rot. Growers are even seeing it in turnips and mustard greens, something I had never seen before. I’d seen it in cabbage and kohlrabi, but this year black rot is just off the charts.”
Black rot causes yellowing of the leaf edges, leaving cabbage unmarketable, and seriously affecting the yield and quality of all brassicas, Anciso said.
“Bacteria in general are hard to control, and there are some biological controls, but black rot is an especially tough guy to beat, if not impossible,” he said.
Onions have also been hard hit by the cool, wet weather, according to Anciso.
“Since mid-February, and with all the wet weather in March, we’ve seen an explosion of onion diseases,” he said. “These include downy mildew, purple blotch and bacterial blight, all of which are very hard to control. It’s difficult to get into the fields to spray fungicides, and even if a grower manages to get in there to treat, subsequent rains just wash off the treatment.”
Onion yields are low, Anciso said. Disease and unfavorable weather are causing early onions to bolt, or flower, making these so-called “seeder” onions unmarketable.
“These conditions cause a cavity in the onion bulb, which develops into a rapid decay. At this point, among the early season onions that are planted before Oct. 7 and harvested now through early-April, about 20 to 70 percent are seeders,” he said.
Onion pickers, who do their work by hand, harvest only the healthy onions, leaving the seeder onions on the ground.
Anciso said onions planted later in the year for later harvesting in late-April to mid-May may not be affected.
“But they will be affected if predictions of continued rains come true,” he said.
Brad Cowan, the AgriLife Extension agent in Hidalgo County, said conditions haven’t improved much for cotton and sugarcane growers.
“They still need an extended period of hot, dry weather to be able to get into their fields to plant either cotton or sugarcane, or harvest mature sugarcane,” he said.
Goldsmith said temperatures will continue to warm as the “polar express” that so often reached the Rio Grande Valley has retreated back into Canada.
“A robust subtropical jet stream that tends to move upper-level disturbances from Baja California across northern Mexico and into Texas is expected to continue through April and probably into May,” he said. “These disturbances can lead to an elevated to significant threat for heavy rainfall and local flooding. In addition, multiple hailstorms and damaging winds become an increasing possibility as spring turns to summer.”
The bottom line, Goldsmith said, is that prolonged hot, dry days will be the exception rather than the rule through May; a better opportunity for such conditions would likely not arrive until June.