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ARS Home » Midwest Area » East Lansing, Michigan » Sugarbeet and Bean Research » Research » Publications at this Location » Publication #317354
Title: Alternaria spp. from sugarbeet tolerant to four fungicide classes in Michigan

Author
item JIANG, QIANWEI - Michigan State University
item WU, HANGHANG - Michigan State University
item KIRK, WILLIAM - Michigan State University
item Hanson, Linda

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 6/10/2015
Publication Date: 1/1/2016
Citation: Jiang, Q., Wu, H., Kirk, W.W., Hanson, L.E. 2016. Alternaria spp. from sugarbeet tolerant to four fungicide classes in Michigan. Phytopathology. 106:S1.4.

Interpretive Summary:

Technical Abstract: Alternaria species have caused minor foliar disease issues on sugarbeet historically. Recently, increased incidence and severity of Alternaria leaf spot (ALS) has been observed in several growing regions. Once defoliation is evident there is a potential to cause yield loss. One possible factor in the increased disease incidence in sugarbeet fields is that the pathogen has resistance to fungicides used for management of other foliar diseases, such as the major foliar disease Cercospora leaf spot. Fungicide resistance occurs in Alternaria spp. on other crops and this could be a factor in ALS on beets. The aim of this work is to test the response of Alternaria spp. from beet to commonly used foliar fungicides in the Michigan sugar beet growing region. Eight Alternaria isolates from the USDA-SBRU culture collection collected from different areas of the United States between 2002 -2009 were included. In 2013 and 2014, Alternaria isolates were collected from several sugarbeet fields as part of the annual Michigan Cercospora leaf spot survey. Isolates were single spore transferred and maintained on V8 juice agar. A spiral gradient dilution method was used to estimate the fungicide concentration which caused a 50% inhibition in mycelial growth or spore germination (EC50). All the isolates tested from 2002-2009 showed resistance to azosystrobin, prothiocoazole and thiophanate-methyl fungicides with EC50 >100 ppm. In 2013, five Alternaria isolates were tested against different DMI fungicides and Organo tin. Isolates tested also showed resistance to all DMI fungicides (EC50 >100 ppm) as well as moderate resistant to tin fungicide. Isolates from 2014 are still being tested. The finding of high levels of resistance to three widely used classes of fungicides indicates that fungicide resistance is present in the Alternaria species on sugar beet and was present even before some of these were registered for use on beets.