As part of on-farm variety testing/disease monitoring programs, Arkansas Extension has been working plots around Cash, Ark., for several years.
“The program has been going for about 15 years in cooperation with our breeding programs and Chuck Wilson (Arkansas Extension rice specialist),” said Rick Cartwright, Arkansas Extension plant pathologist, at the recent Cache River Valley Seed field day near Cash, Ark. “We try to put advanced lines, near varieties, and standard varieties into different cropping situations.”
Arkansas is blessed to be able to grow rice in many different environments. “That's different from other states. We don't have a single environment we're trying to produce rice in. So, to get a variety that will hold up under all the state's growing conditions is very difficult. Some perform well in southeast Arkansas and not so well elsewhere.
“We try to assist the breeding programs in getting these rice types, once they're advanced enough to get seed, out in the field. That exposes them to all the different environments we can't entirely reproduce on the stations.”
The plots around Cash are small. “We don't have a lot of seed sometimes. They are replicated so we can get more than one look at them at a location.”
These are also replicated as sites across the state. Annually, between 15 and 20 of the sites are set in very different environments — “from the southern border all the way north, almost into Missouri. The interesting thing about diseases is they develop within their own small environment. In one environment, one disease will be very intense. In another environment, the hot disease will be different. Here, for example, it's a wide-open field and there's sheath blight. In a field surrounded by trees, there will be a blast epidemic.”
Out of all this research, the Extension Service produces an information sheet. “It will help you select a variety that will perform to its maximum potential in your environment. That's what we're shooting for.”
Farmers on the Grand Prairie produce rice one way. In Craighead County, “you'll produce it a bit differently. We want both areas to have a variety and management package that maximizes yield potential.”
Many developing Clearfield lines are in plots around Cash. The lines are being evaluated for characteristics and how they hold up. Mixed into the plots are CL 161, the new CL 171AR, and the Clearfield hybrids.
“At this time CL 161 is very susceptible to sheath blight. It's pretty much routine to have to manage sheath blight with a fungicide at an early growth stage.”
CL 171 was released with “a bit better” disease package that is still being assessed as it moves through the program. “But we're hopeful it'll be more resistant to sheath blight. In the field, it seems to be holding up better to blast under extreme situations than CL 161.”
The hybrids have a very good disease package, said Cartwright. However, as time passes, “the hybrids do seem to be getting a little more susceptible to sheath blight. As hybrids have evolved, they can withstand higher rates of nitrogen.
“It used to be we were afraid to fertilize them too much for fear of them falling down. These new hybrids hold up better, in my experience, so farmers are pushing them with high rates of nitrogen.”
Unfortunately, when that's done, it makes the plant more susceptible to sheath blight. That's true almost no matter the variety.
This year, “you've probably heard me say we need to watch CLXL 730. That's because last year, for the first time, we began getting yield responses on that variety after applying a fungicide for sheath blight control in plots.
Cartwright has recently fielded many questions about narrow brown leaf spot, an airborne disease that is usually a minor, late-season problem in the Mid-South. It is caused by a fungus similar to the one that causes frogeye leaf spot on soybeans. Last year, narrow brown leaf spot damaged some Louisiana and north Arkansas rice.
The disease is only now developing in CL 161. “It won't do any damage because it's so late. It can blank out part of the head if it gets in early enough and conditions are right.”
Although not yet a major concern, “we probably need more work more on it. Locally, as our climate seems to be changing, this disease appears to be increasing in importance in the South.”
What to do with narrow brown leaf spot? “We know the fungicide Tilt — a triazole — is active on the brown leaf spot fungus. The fungicide in Quadris is not active on it. If you're using a kernel smut prevention program with Tilt, Stratego or Quilt, that should minimize narrow brown leaf spot. Research in Texas and Louisiana shows that a 6-ounce rate of the fungicide was better than the 4-ounce rate sometimes used in smut prevention.”