Location: Sugarbeet and Bean ResearchTitle: Azoxystrobin sensitivity testing in Rhizoctonia solani AG2-2 populations affecting Michigan sugar beet
|WILBUR, JAMIE - Michigan State University|
|BLOOMINGDALE, CHRIS - Michigan State University|
|MINIER, DOUGLAS - Michigan State University|
Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/30/2019
Publication Date: 10/1/2019
Citation: Wilbur, J.F., Bloomingdale, C., Minier, D.H., Hanson, L.E. 2019. Azoxystrobin sensitivity testing in Rhizoctonia solani AG2-2 populations affecting Michigan sugar beet [abstract]. American Phytopathological Society. 109(10S):S78. https://doi.org/10.1094/PHYTO-109-10-S2.1.
Technical Abstract: Rhizoctonia root and crown rot (RRCR) is caused by Rhizoctonia solani AG 2-2 and continues to be a major pest of sugar beets. In Michigan, azoxystrobin (Quadris) is widely applied to manage RRCR. Azoxystrobin, a quinone outside inhibitor, targets a single site to inhibit fungal respiration and so possesses a high risk of fungicide resistance development. Continued reliance on one to two applications of this product per season has prompted investigations of azoxystrobin sensitivity in Michigan R. solani populations. Isolates were collected from research and commercial fields in the Michigan sugar beet growing region. Two additional baseline isolates, collected prior to azoxystrobin use in sugar beet, were included for comparison. Isolates were screened in half-strength clarified V8 agar amended with salicylhydroxamic acid at 10 µg ml-1 and azoxystrobin at concentrations: 0, 0.01, 0.1, 1, 10, and 100 µg ml-1. After 96 hr, mycelial mats were removed from media, air dried for 48 hr, and mass was measured. Percent inhibition was calculated and effective concentrations for 50% inhibition of colony mass were determined using three-parameter logistic regression. In a preliminary screen, azoxystrobin insensitivity was not observed in Michigan R. solani populations, however, additional testing is ongoing. Evaluation of azoxystrobin efficacy, and potential alternatives, for RRCR management will be conducted at the Saginaw Valley Research and Extension Center in Frankenmuth, Michigan.