Fungicide studies and besting blast through genetics
Aug 31, 2006 10:03 AM,
By David Bennett
Farm Press Editorial Staff
While certainly unwelcome, the arrival of Asian soybean rust has meant a peripheral benefit for row crops.
CARTWRIGHT
“ASR has led to more fungicides being introduced and developed in the United States,” said Rick Cartwright, Arkansas Extension plant pathologist at the recent Southeast Branch Station field day in Rohwer, Ark. “We haven’t had a bunch of good ones until relatively recently.”
Some of the newer products will likely be available for rice as well as soybeans. To get a “head start” Cartwright, along with fellow plant pathologist, Cliff Coker, have many tests set up around the state. The studies are checking not only the new products’ effectiveness but also any phytotoxicity.
“One of the things we use in disease management for all crops is genetic resistance. It may not offer total control of a disease, but it’s pretty handy. Even a bit of genetic resistance can make other management practices, including fungicides, perform much better
“We do these evaluations both on-station and off in cooperation with our county Extension agents. We pay special attention to those at this time of year to get a feel for what the new varieties offer — not only in yield and quality potential but in disease resistance potential.”
Blast
Blast is among the major Arkansas rice diseases, especially in the southeast. Genetic resistance is the primarily weapon in the battle with the disease.
“Right now, one of our highest yielding varieties is Francis. On good soils, Francis is hard to beat. But on blast soils, it’s very susceptible so you must be careful where it’s planted. We are using Francis very successfully on 10 percent, or so, of the acres in the state.”
Another variety, Banks, is similar to Francis and was released several years ago. Banks is a good illustration of what can happen when there’s only a single resistance gene in a plant.
“It provided good control of blast races that were common at the time of its release. But it’s also easy for the fungus to change. Over time, that fungus finds a way to do damage.
“So Banks started out resistant and now it’s susceptible. Remember that. Even though Banks was (a University of Arkansas release), I’m tired of looking at neck blast on it.”
Other varieties resistant to blast include several from LSU like Clearfield 131 and CL161, Cheniere, Cocodrie and Trenasse. The University of Arkansas also has Cybonnet.
“Of all those, Cybonnet has the best blast resistance, by far. It has multi-gene blast resistance but it’s very susceptible to sheath blight so there’s a trade-off.
All the LSU varieties behave similarly to blast in the field.
“If you look, you’ll find some leaf lesions but the disease doesn’t progress to neck rot. I have confidence in the LSU varieties. With good management, I believe you can grow them even in blast situations without much fear.”
However, as a general rule, “if you’ve got a blast problem the hybrid rice is best. If you can afford them and you’ve got sandy soils, they’re the best choice. Cybonnet is next.”
Editor’s note: to read this story unabridged, see the Delta Farm Press tabloid.
e-mail: dbennett@farmpress.com
