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Research Conducted
In 2017 and 2018, over 400 soybean fields in 31 counties were evaluated for the prevalence of stem diseases. Fields were surveyed during early maturity, and stems were evaluated for charcoal rot, pod and stem blight, phomopsis seed decay, northern stem canker, white mold, anthracnose, phytophthora stem rot and other diseases. Results of this study give North Dakota soybean growers and researchers data on which diseases are most common, which diseases may be causing yield loss, and where improvements in disease management can be made.

Why is the research important to North Dakota soybean farmers?
Multiple stem diseases can cause yield loss on soybeans. In some cases, cost effective management tools (such as rotation recommendations or selection of a resistant variety) are available. However, without a better understanding of the prevalence of these diseases, and tools that facilitate easy identification of these diseases, growers are more likely to experience yield loss.

Final findings of the Research?
In 2017 and 2018, 4,020 and 4,100 stems were evaluated for soybean diseases in 31 counties (Table 1). The most commonly identified diseases were those caused by Diaporthe/Phomopsis species, which are primarily residue borne pathogens and favored by short crop rotations. Charcoal rot was concentrated in the southeastern soybean growing counties, particularly in Cass, Traill and Barnes, where surveyors also noted large areas of fields dying prematurely. White mold and Phytophthora stem rot were less common, but both diseases need adequate rainfall (2017 and 2018 were relatively dry). Anthracnose was common, but rarely causes yield loss as is not considered a cause for concern. Brown stem rot was visually identified in both years, but molecular diagnostic confirmation is currently underway.

Benefits/Recommendations to the North Dakota Soybean Farmers and Industry:
This survey provides robust data on the prevalence of stem diseases occurring in North Dakota, and gives soybean growers (and others) information on what diseases they may expect, and subsequently manage (if possible). We recommend that soybean growers scout their fields and identify the diseases that are occurring. Improved tools to help growers identify diseases have recently been developed, such as the Soybean Disease Diagnostic Series (PP1867), are available. Importantly, this survey was conducted in two relatively dry growing seasons (2017 and 2018), in wetter growing seasons, we would expect more white mold and late season Phytophthora stem rot.