Fungus blight kills tomato plants in North Texas
09:44 AM CDT on Thursday, July 1, 2010
By MARIANA GREENE / Garden editor email@example.com
Last year, most of the eastern half of the United States was hit by a wide-ranging plague that ruined one of the most delectable joys of summer â€“ the sun-sweetened, vine-ripened, juicy tomato. The airborne, far-ranging blight destroyed backyard plantings, farmers' fields and corporate commercial crops alike. It spared almost no one.
We in Texas could only sympathize from afar, as the red juice dripped down our chins.
The late fungus blight, as the dastardly disease is called, didn't affect us in Texas. It turns out that our early blast-furnace temperatures are good for something: They usually prevent late fungus blight from gaining a toehold on our tomato plants.
Before you gloat, know that late blight is not the only disease in Mother Nature's repertoire. There's a late blight, and there's an early blight. While the common names make no sense as far as the timing of the disease's onslaught, the fact remains that we in North Texas are under siege from early blight.
"I toured community gardens, home gardens and commercial gardens this past week, and the tomatoes look like hell everywhere," says Morning News garden columnist Howard Garrett.
He could have been describing the tomatoes planted in large terra-cotta pots on my blazing-hot driveway. In midspring I was relishing the tartness of my homegrown grape-size fruits of the season. They never made it into a salad; we picked them as they ripened and popped them into our mouths. The vines were lush and blooming, showing promise of climbing way up bamboo supports.
Then the lowest leaves started turning yellow, and it was downhill from there. My tomato plants, I now know, were infected with early blight.
Like late blight, early blight (also called Alternaria leaf spot) is a fungal disease spread by spores. It can overwinter in the soil and is easily transmitted to the lowest leaves of those transplants you tucked into the dirt in early April. Every time you splash a drink from the hose onto the soil around each plant's stem, you run the risk of propelling the fungus spores onto the lower leaves of the tomato plant.
Once the fungus reaches the lower leaves, it easily moves up the plant, infecting leaflet by leaflet, turning each, by turns, yellow and then crisp brown. Dead.
Although tomato plants in North Texas vegetable gardens can be infected with the late blight (Phytophthora infestans), it is usually less of a problem here than what the Northeast is dealing with for the second summer in a row. "We get hot quick, and that works in our favor," says Dr. Kevin Ong, director of the Texas Plant Disease Diagnostic Laboratory in College Station. "The fungus itself thrives on moist conditions, cool nights and warm days. Typically, for us, we get a real short period of that."
He won't say it could never happen. "If we get a cold front come through and cloud cover holds the humidity in, with six to 10 overcast days of cool nights and mild days," late blight could develop on tomatoes. Cool nights? In Dallas? In July, August or September? Nah.
"When it dries out, late blight dissipates real quick," Ong says, his tone clearly indicating he does not expect late blight to be an issue here.
Early blight, however, is another story. Tomato plants should never be watered from overhead, period. If you water with a garden hose, you also are inviting trouble. A single splash can mean doom for your crop.
"Early blight is closely tied to environmental conditions," Ong says. He instructs home gardeners to thickly mulch the top of the soil around a tomato plant and to water plants via drip irrigation.
Garrett recommends several precautions to take at planting time in hopes of preventing the blight from developing in the first place. Organic remedies, he says, might set the disease back, but the blight is tough to eradicate once it shows up on your tomato plants.
Set the transplants in place, says Garrett, apply cornmeal to the soil around the transplant and top with shredded bark mulch. Spray the plants with Bio-Wash by 1st Enviro Safety Inc., a product Garrett says will kill the fungus if it is present.
As an extra measure of prevention, he advises, dip the plants' rootballs into 1 gallon of water mixed with one-fourth cup of whole-ground cornmeal.
If your spring-planted tomatoes have blight, there's little hope of bringing them back at this point. The good news is that it's time to plant fall tomatoes, and transplants should be at retail nurseries now.
I'm starting over, and I will try these precautions. Discard the plants, but discard the dirt, too, if you are growing tomatoes in containers. If your tomatoes are growing in garden soil, don't plant them in the same spot.
Meanwhile, I'll be a regular at the Dallas Farmers Market to buy just-picked, vine-ripened tomatoes from East Texas growers â€“ while the season lasts.