Choose Soybean Varieties Carefully
 to Combat These Two Diseases
 

White Mold....

It's getting to the point where the "taking my chances" strategy with sclerotinia, or white mold as it is usually called, is becoming a costly one. White mold was a disease widely seen throughout Wisconsin and in Fond du Lac County soybean fields in 1997. Although the list of factors that influence white mold is lengthy, realistically there is only one major defense for most soybean growers ----- variety selection. That is, of course, unless you're willing to make a major management change in tillage practices or row spacing just to manage one disease at the expense of giving-up production for other reasons. At Galesville and Hancock, two locations in the 1997 UW variety tests with intense white mold pressure, incidence of white mold ranged from 5 to 61 percent across 93 varieties. How much did this impact yield? The variety with 5 percent infection averaged 51 bushels per acre compared to the 65 percent infected variety with a yield of only 29 bushels. Unless you are planting a first-year field of soybeans, white mold tolerance/resistance simply MUST be a component of your selection criteria. The best place to get this information is from the UW Soybean Variety Performance Bulletin (available from the UW Extension office).

Phytophthora Root Rot...

Like white mold, phytophthora root rot seems to be easier to find in area soybean fields with each passing year. In 1997, some fields suffered yield reductions of nearly 50 percent from a combination of early and late phytophthora infections. These yield infections did not just occur in low, wet areas but also on fields that would be considered well drained. The easy explanation is that soybean acreage has increased dramatically in the past ten years with more fields now having long histories of soybean production. It appears that disease organism populations are building in many of these fields. When making variety selections, don't overlook phytophthora gene resistance (compared to only tolerance) as a component of the performance package. For maximum protection, focus on those varieties with Rps 1k gene resistance. Once again, this information is available in the UW Soybean Variety Performance Bulletin.