Biocontrol of Sclerotinia Promising
Biological control of Sclerotinia shows promise
While the best means of controlling Sclerotinia in sunflower are hybrids that are more resistant to the fungal disease, crop scientists are also looking at other means of control, since the best line of defense will come from using a combination of approaches.
Two biological means of controlling Sclerotinia show promise. They are basically parasitic microbes that feed on Sclerotinia sclerotiorum, the organism which causes the fungal disease. One is a commercial formulation called Contans, which is used in Germany to suppress white mold in canola, but is not yet registered for use in the United States. The other bio-control agent is Sporidesmium, a bio-control agent that has been researched for over 15 years, but never commercialized.
“Both of these fungi love to chew up Sclerotia,” says USDA-ARS plant pathologist Tom Gulya. Both bio-control agents can be found naturally in the soil. Researchers are hoping to find a way to manage them for use in controlling Sclerotinia when the disease develops.
Gulya is experimenting with the bio-control agents in a conventionally-tilled field plot near Oriska, ND, and a no-till field plot near Pekin, ND. Both fields had severe head rot infection in 1999. He’ll be planting sunflower in the two plots in 2001 and 2002 to analyze the effectiveness of the two bio-control agents.
Sporidesmium appears to be the more effective of the two. However, the fact that it can be found naturally in the soil also makes the addition of supplemental Sporidesmium more difficult to analyze, Gulya notes. Further, it is harder to reproduce, and thus commercialize.
“It can be a big hurdle to move it from the lab to a small field plot, and then to move it from a field plot to actual field conditions can be an even bigger hurdle. The ability to grow large quantities of it, store it on the shelf and maintain its effectiveness could get to be quite expensive and more difficult to manage than conventional chemicals. So the commercial phase could be a real challenge,” says Gulya.
Since 1995, Iowa State University plant pathologist Charlie Martinson has been researching bio-control agents for suppressing white mold on soybeans. The practice has proven to be effective, with 100% control in some cases. He agrees that the cost-effectiveness of bringing bio-control agents to market presents a challenge. Research indicates that bio-control agents are so successful in suppressing Sclerotinia that they may provide effective residual control, meaning treatments may not be needed every year. This may be another factor that could limit cost recovery for bio-control product development.
Still, Martinson is hopeful that further research will result in more efficiencies in developing bio-control agents, and thus make commercialization more feasible. He points out that the development time for reproducing the bio-control agent in the lab can be completed in half the time it used to, but that further improvements are still needed if bio-control products are to be viable commercially.
Martinson, who is nearing retirement, predicts he will spend the rest of his career working on bio-control research of Sclerotinia/white mold. “We have to be able to produce large amounts of inoculum (of the bio-control agents that control Sclerotinia) cheaply, and right now, that’s not easy to do. But I think we can,” he says. – Tracy Sayler
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