Location: Sugarbeet and Bean ResearchTitle: Alternaria leaf spot in Michigan and fungicide sensitivity issues
|ROSENZWEIG, N - Michigan State University|
|JIANG, Q - Michigan State University|
|SAMOHANO, P - Michigan State University|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/15/2017
Publication Date: 12/1/2017
Citation: Hanson, L.E., Rosenzweig, N., Jiang, Q.W., Samohano, P. 2017. Alternaria leaf spot in Michigan and fungicide sensitivity issues. Phytopathology. 107:S5.64.
Technical Abstract: Since 2010 there has been an increase in identification of Alternaria leaf spot on sugar beet in Michigan and other growing regions in the US and Canada. In 2016, the disease was severe enough to cause economic losses in the Michigan growing region. Michigan isolates from sugar beet were examined for species identification and tested for their response to fungicides commonly used on sugar beet to control foliar diseases. All isolates collected belonged to the Alternaria alternata species complex by both morphological and DNA sequence analysis. From 48 isolates collected in 2016, and 38 isolates collected in prior years, over 50% were identified as having resistance to one or more of the major fungicides currently used on sugar beet, including quinone outside inhibitor, demethylase inhibitor, and organo-tin fungicides. In addition to fungicide sensitivity, isolates were screened for pathogenicity on an alternate host, tomato, and for virulence on sugar beet germplasm. All isolates tested infected tomato fruit. Varietal differences in response to the isolates were observed in sugar beet germplasm. Further research on management options is needed for this disease.