Elizabeth Bause, NDSU Department of Plant Pathology
Andrew Friskop, NDSU Department of Plant Pathology

Corn diseases are found regularly in North Dakota, yet their prevalence and severity have never been formally documented. Understanding the diseases that occur in the state and understanding which diseases pose the greatest economic threat will help drive future management decisions for growers. The objectives of this project will help document corn diseases in North Dakota, assess the yield loss potential of Goss’ leaf blight and wilt (Goss’ wilt), and develop a better understanding of the bacterial pathogen responsible for Goss’ wilt.

A corn disease foliar survey has been conducted in North Dakota since 2014. Results from the survey have determined that three diseases commonly occur in the state; common corn rust, northern corn leaf blight and Goss’ wilt . The incidence of these diseases have varied from year to year, however common corn rust continues to be the most prevalent disease. Common corn rust and northern corn leaf blight rarely need to be managed as most northern hybrids have adequate resistance. However, several hybrids are susceptible to Goss’ wilt. Hybrid selection can influence both the prevalence (how often it appears) and severity (how much of the plant is damaged) of this disease.

Hybrid selection is an important decision made by a grower each year. Many factors can drive the selection process such as maturity and yield potential. Another factor that may influence hybrid selection is disease (i.e. Goss’ wilt). Understanding the yield loss potential associated with Goss’ wilt will help create awareness among ND growers. Trials have been conducted since 2015 to determine the effect of inoculation timing (infecting corn plants with the Goss’ pathogen) and hybrid susceptibility on yield. Research plots were inoculated at growth stage V8-V12 and/or VT. All the data were compared to plots that were not inoculated with the pathogen. Results in 2016 showed substantial yield loss in both susceptible and intermediate hybrids. For example, when the pathogen was inoculated at growth stage V8-V12, yield losses of 55% and 34% were observed on susceptible and intermediately resistant hybrids. Another way to look at this data is if a producer assumes a susceptible hybrid has 170 bu/A yield potential, an early season infection by the Goss’ wilt pathogen may reduce yields to 94 bu/A in infected areas.

One of the cornerstones of plant pathology is understanding the causal agent of a disease. It has been well documented that several plant pathogens have changed over time in numerous cropping systems. In order to understand Goss’ wilt risk in ND, more information is needed on the biology of the pathogen. In the upcoming year, approximately 80 Goss’ wilt pathogen isolates will be used to assess aggressiveness (how quickly the pathogen spreads on leaf tissue). Aggressiveness will be assessed by measuring the lesion length over time and determining if certain isolates produce disease symptoms faster than others. The information could aid future breeding efforts.

The research listed above will help create and strengthen corn disease management recommendations for North Dakota. The survey will help monitor any changes in disease prevalence, the Goss’ field trials will help determine yield loss potential, and the aggressiveness studies will enhance our knowledge on the biology of the Goss’ wilt pathogen. This information will used in Extension talks to help create awareness and management options.