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Intercept White Mold
June 01, 2002

Mike Clemens kneels in a field he is preparing to plant. The soils bare, but the Intercept WG that he applied the previous fall is busy breaking down white mold sclerotia, reducing the amount of spores that potentially could be released to infect the future dry bean crop with white mold.

Mike Clemens, Wimbledon, N.D., is trying a new method in white mold control.

Last fall, he applied a product called Intercept WG to some of the fields that he planned to plant to dry beans.  Intercept WG contains live spores of the fungus, Coniothyrium minitans.

This organism attacks and destroys sclerotia  the hard, resting structures of Sclerotinia minor  before they germinate and cause white mold.

Intercept WG has been used in Europe for four years and in the U.S. for one year. In the U.S., Intercept WG is cleared for use on all agriculture soils. It can be used on dry beans, sunflowers, flax, potatoes, canola, lettuce, tomatoes and all other crops susceptible to white mold.

Intercept WG won quick government approval because it is neither a chemical nor a biotech compound. The spores it contains occur naturally in the soil. The Organic Materials Review Institute has even okayed its use.

Intercept WG offers a unique way to control white mold. Rather than attacking white mold when it appears on plants or enhancing plants defenses, Intercept WG breaks the diseases life cycle so it doesnt have the chance to infect plant tissue.

This is an exciting development in white mold control, says David Goulet, president of Encore Technologies, Minneapolis, Minn., the firm distributing the product in the U.S.

Really works

Intercept WG does reduce sclerotia in the soil, confirms Luis del Rio, a North Dakota State University plant pathologist, who is conducting trials at the Carrington Research and Extension Center and at Fargo this year.

Independent lab and plot trials conducted widely in Europe, and at Cornell University in the U.S., show that the number of sclerotia in the soil drops dramatically after as little as three months.

In the Cornell study, researchers seeded a plot in June with sclerotia collected from a field or dry bean screening. They sprayed it with 4 pounds of Intercept WG per acre with 100 gallons of water per acre and planted wax bean seeds in the plot. In October, they collected the soil and recovered the remaining sclerotia. They found only half the number of sclerotia they had placed in the plot, and all of those had decomposed. In the control plot, the number of sclerotia in the soil increased 150%.

Yield trials hold similar encouraging news. No trials have been conducted yet on dry beans, but in Wisconsin 30 trials over two years on snap beans Intercept WG beat a foliar fungicide application under all disease situations. The best control came from a combination of Intercept WG applied to the soil in the spring and a foliar fungicide application during the growing season.

Because white mold spores can blow in from untreated fields it is logical that the combination provides the best control, Goulet says.

To review these and other trials, go to Encores website, www.

NDSU plant pathologist Luis del Rio will be conducting trials on Intercept WG this year.

del Rio says he has several questions about Intercept WGs use in dry beans, including

  • Will it be economical?  A single application, at a rate of 1 pound per acre, costs $9-$10 per acre. Higher rates may be necessary and farmers may have to apply the product several years in a row to make a significant impact on white mold spore levels in a field.
  • Will spores that blow in from untreated fields infect the crop so significantly that reducing sclerotia population in the field is not important?
  • Should it be applied in the fall or spring? Encore recommends that Intercept be applied at least 45 days before the crop is infected, or in the fall if other cultural practices permit. The longer Intercept WG has to work, the better the results. At the University of Wisconsin, researchers applied Intercept WG in the spring.
  • How will soil pH affect its performance? Trials in Arizona show little difference in performance based on soil pH. del Rio wants to judge the interaction between Intercept WG and North Dakota soils.

More Biologicals Coming

NDSU researchers are looking at several other biological products for white mold control, says Luis del Rio, NDSU plant pathologist.

All are still in experimental stages of development, but appear promising. NDSU scientists are also investigating the use of the herbicide, Cobra, to reduce white mold. Some studies show that applying Cobra reduces white mold in soybeans. The herbicide burns foliage, which opens up the canopy and lets in more air and sun to dry the plants. The stress from the herbicide also causes the plants to toughen their natural defenses against infection.

It works like a vaccine does in the human body, del Rio says.

Anxious to try

Despite these and other questions, Clemens decided to try Intercept WG this year. He grows dry beans in a rotation that includes sunflowers, a crop that also is a major host for white mold. Sclerotia levels are high in some of these fields.

Clemens split one field this year so he could gauge Intercept WGs impact.

It will be interesting to see what happens, he says.

For more information on Intercept WG, see the website: or call (952) 404-9596.


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