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Fungicide for Sclerotinia (White Mold) Stem Rot Management
Crop rotation is important for the management of Sclerotinia stem rot, although it is not a cure-all since Sclerotinia spores may blow in from nearby fields. Try to avoid planting more than one highly susceptible crop in a rotation. Highly susceptible crops include borage, canola, crambe, sunflower, dry beans, lentils, chickpeas and soybeans. Field peas are much less susceptible, particularly the semi-leafless types, with production of sclerotia low compared to canola. Flax has a very low level of susceptibility and produced no sclerotia in irrigated trials at Carrington. Thus, flax and semi-leafless field peas might work in a rotation without being severely damaged and without doing much to maintain or build up a sclerotinia population.
Fungicides Registered for Sclerotinia in Canola
Quadris is registered for Sclerotinia on canola. It is to be applied at 10%-25% flowering (3-7 days following first flower) at 9.6 fl oz/A. This ounce rate effectively controlled Sclerotinia in 1998 in a Bottineau county trial and in trials across western Canada, but has not been effective in some trials in western Minnesota.
Ronilan is registered on canola. It is to be applied at 20-50% flowering (4-8 days following first flower) at 10.6 to 16 oz/A. The 12 oz rate would normally be used. This rate has been effective in Canada and in trials in Minnesota and North Dakota. The 50% flowering stage is time of maximum color; at that stage there will be a few buds remaining at the top of the main stem. Thiophanate methyl (several formulations) is registered. Apply at 20-50% flowering. Split applications are labeled. Boscalid is labeled at 6 oz/A at 20-50% flower.
Two items can be used to help make decisions on use of a fungicide: the Sclerotinia risk map and the Sclerotinia check list.
See additional articles in this ProCrop section for details.
Canola growers should consider a fungicide only if they have a good yield potential (40 bu or more), since the chances of an economic return are higher and the potential for Sclerotinia is also higher.
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