FUNGI IN THE SPOTLIGHT

Grand Rapids, Minn. -- An otter makes a trail in the waves, a flock of ducks flies into the wind, and Bob Nyvall grins. He's clearly in his element as he gazes out over the blue-black water of Dick Brink's wild rice paddies.

Nyvall loves the outdoors, history and a bit of mystery. Combine that with a love of science, and you've got a researcher who's bound to get at the bottom of the disease that threatens northern Minnesota's cultivated wild rice.

If Nyvall, a plant pathologist at the U of M's North Central Experiment Station, doesn't yet have that disease's number, he does have its name -- Bipolaris oryzae or fungal brown spot. That's something, because growers had been spraying fungicides for Bipolaris sorokiana, an early spot blotch that Nyvall discovered doesn't harm wild rice yields. Initial research showed that the two diseases, which look essentially the same on a wild rice plant, are two distinct organisms. So before his work is done, Nyvall has already saved growers like Brink thousands of dollars in unnecessary spraying.

Brown spot questions
The big question now, says Nyvall, is finding out where fungal brown spot overwinters so the growers can attack it successfully. "We're trying to save them the cost on that second disease that is really doing the damage," says Nyvall. "If we can figure out where [it] overwinters, we can probably save them millions of dollars." With about 50 Minnesota growers, cultivated wild rice has a $50 million impact on the state's economy, Nyvall says. Fungal brown spot can destroy up to 100 percent of a grower's crop.

Nyvall and his graduate assistants work in a greenhouse, experimenting with water taken from the rice paddies. They examine samples microscopically for evidence of fungus, comparing test and control samples throughout the summer and harvest. "We hope to find a pattern," he says. "We know it can survive if it's high and dry. When it becomes flooded, it can't survive. But what is it about a rice paddy that allows it to survive?" The research is "incredibly labor-intensive," Nyvall says.

Four years of research has ruled out airborne sources for the fungus, and the disease can't survive on rice plants through the winter. Nyvall is also certain it doesn't survive on neighboring grasses, and he's concentrating now on residue floating on the water. Three growers participating in the study -- Ross Rennemoe of Washkish, Rod Skoe near Clearbrook, and Tom Godward near Aitkin -- provide paddies far enough away from each other for a good survey. Samples are taken weekly.

Research last year showed rice plants to be most susceptible to fungal brown spot during the flowering and reproductive stage. Nyvall has identified three crucial criteria: high fungus innoculum numbers; temperature and humidity high enough to support growth, and the plant's reproductive stage.

Flood the fields
Even at this early stage of AURI-PRO research, Nyvall says, growers have adopted practices that save money and reduce fungicide use. Spraying should be delayed as much as possible, he says, and flooding does help control the disease. Many growers tried spring flooding this year, and will drain the paddies later in the season to reduce plant stress.

The university has developed several varieties of wild rice, Nyvall says, that should help growers cope with disease. "What we've tried to do in an evolutionary sense is domesticate a wild plant in just a short period of time ... Even though we haven't cracked this nut yet, we've learned so much about the entire disease complex. All of that has been beneficial to growers, so once we discover (the disease source), we'll have done quite a lot."