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Controlling Sclerotinia Naturally

Monday, February 3, 2003
filed under: Disease

There’s no questioning that Intercept WG is effective in attacking and breaking down Sclerotia in the soil. After a full year of use in 2002, growers and crop scientists know more about the new biocontrol product, but are still looking for another year or two to fully assess just how well Intercept works.

Approved by the Environmental Protection Agency in spring of 2001, Intercept WG is labeled for higher-value crops in other parts of the country as Contans WG. It is literally a fungus-fighting fungus: the product’s active ingredient is Coniothyrium minitans, a parasitic fungus that feeds on Sclerotinia sclerotiorum, the organism which causes Sclerotinia/white mold. Once applied, Intercept WG attacks and destroys Sclerotia, which are the hard, black bodies that fall to the soil and reproduce the disease.

Unlike chemical fungicides that protect the plant, Intercept kills the pathogen in the soil. It is a naturally-occurring parasitic fungus, and won’t harm plants, animals or water quality. In fact, the product is listed by the Organic Materials Review Institute (OMRI) for use in organic production, It is targeted to control Sclerotinia (white mold) in crops such as dry beans, snap beans, potatoes, canola, flax, soybeans, safflower and sunflower.

Encore Technologies is the U.S. product distributor for Intercept WG. Reg Herman, who farms west of Devils Lake, N.D., is a grower and product dealer. Last year, he applied Intercept at rates of 1 and 2 lbs/ac. “I experimented with low and high end of recommended rates, and I think now that 1 lb/ac is on the lighter side of what should be applied. I think 1.5 lbs/ac is appropriate.” Product cost at the 1.5 lb rate would be about $16 per acre.

Herman stresses that the product is not like a fungicide or herbicide: after it’s applied, it needs time to break down the Sclerotia bodies in the soil.

Encore is also learning that the product— essentially consisting of living micro-organisms—might be damaged if it is tank-mixed with some pesticide products, or sits in a tank mix very long. “I would be uncomfortable about letting it sit in a tank mix overnight,” says Herman. Roundup and Treflan are two products compatible with Intercept in a tank mix; see Intercept’s product label for more details on compatibility.

Application directions for Intercept advise applying the product at or before planting prior to an anticipated Sclerotinia disease outbreak, by dissolving the product in water, applying it, then lightly incorporating it into the soil. The need for incorporation is one thing that crop scientists are analyzing.

In early results at the USDA-ARS Northern Great Plains Research Laboratory in Mandan, N.D., there was less Sclerotinia stalk rot on plots treated with Intercept, compared to untreated plots. Further, the no-till plots treated with Intercept had less Sclerotinia compared to Intercept-treated plots that were tilled.

North Dakota State University plant pathologist Luis del Rio is involved with another study at Intercept with testing near Carrington and Fargo. The tests which began last year (and are supported in part by the Sclerotinia Initiative) evaluated a number of conditions, including application rate (0, 1, 2 lbs/ac) incorporation (no-till and disking), tank mix compatibility (with Harness, Lasso, Python, Valor, Balance, Prowl, and Authority, herbicides used in crops planted in rotation with dry beans, canola, and sunflower), and application timing (spring, fall).

Del Rio says results are too preliminary to make conclusions. As well, dry and warm weather spells during flowering at both testing locations limited Sclerotinia infections, and hence, testing results. However, he does say that Valor, Harness, and Lasso reduced the effectiveness of Intercept by 50%. The other products appear to be safe to mix with Intercept, but further testing is needed, says del Rio, and the same study will be repeated in 2003.

Herman says he received mixed reviews about the product’s on-farm performance last year. He’s received unsolicited testimony from one confection sunflower processor in North Dakota of a grower who compared the product side-by-side in his sunflower field. The difference in the treated versus untreated was noticeably different. The difference was evident at delivery to the processor too: The sunflower left untreated had a Sclerotinia content of 1.4%. In sunflower harvested from ground treated with Intercept, the Sclerotinia was 0.6%.

“On the other hand, there were instances where the weather and infections last year were so severe that I don’t think the application would have mattered.” Sclerotia produces spores which can be windblown and travel some distance under the right conditions.

Herman says Intercept is similar to a fungicide in the respect that the products can suppress disease, but are not foolproof under severe conditions. “There are years when I’ve applied Tilt and Folicur on wheat and it really made a difference, and there are years I couldn’t tell where I put it down.”

Herman advises producers who grow broadleaf crops in areas susceptible to Sclerotinia/white mold to at least experiment with the product on some of their acreage. “Farmers have to be cautiously progressive. It’s those guys who are trying new products, new varieties, or new crops who seem to be making a better go of it.”

More product information can be found online at Click on the “products” link, then “Intercept WG.” Herman can be contacted by phone at 800-726-5041, or by email: – Tracy Sayler
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