Monitoring the Distribution of Downy Mildew, Verticillium and Charcoal Rot on Sunflower: a Multiple States Approach
Project Number: 5442-21000-039-07
Start Date: Apr 15, 2010
End Date: Sep 30, 2014
New downy mildew races were found in 2009 which overcome the commonly used resistance genes in most commercial hybrids, but the true distribution of these new races is unknown. We propose to enlist pathologists in neighboring states (SD, NE, KS, CO) to systematically sample sunflower fields, collect samples of diseased plants, and have the downy mildew samples typed to race in greenhouse tests in Fargo. Secondly, we have identified charcoal rot in a Minnesota sunflower field, and this is the first report. With increased incidence of charcoal rot on other hosts in the Northern Great Plains, we need to determine the distribution of the causal fungus. The most accurate way to do this is via a soil bioassay and not be assessing disease incidence, which is highly dependent upon weather conditions. The same soil samples will be sent to a commercial lab to isolate Verticillium.
We will use university personnel in North Dakota, South Dakota, and Nebraska to survey 200 fields in early summer for downy mildew and to collect soil samples. The soil samples will be shipped to an ARS lab in Tennessee for a Macrophomina assay and to a commercial lab to isolate Verticillium, and the fields testing positive will be surveyed late in the growing season to assess the severity of charcoal rot and Verticillium wilt. Downy mildew samples will be used in greenhouse tests to determine races of the pathogen.