Optimizing techniques for evaluating Cercospora leaf spot in a Michigan field nursery

Authors: Goodwill, Tom; CORDER, HOLLY - MICHIGAN STATE UNIVERSITY; Hanson, Linda

Submitted to: Journal of Sugar Beet Research
Publication Type: Abstract Only
Publication Acceptance Date: 1/1/2019
Publication Date: 2/28/2019
Citation: Goodwill, T.R., Corder, H.J., Hanson, L.E. 2019. Optimizing techniques for evaluating Cercospora leaf spot in a Michigan field nursery [abstract]. Journal of Sugar Beet Research. 56:81-82.

Interpretive Summary:

Technical Abstract: Cercospora leaf spot disease nurseries were run in Colorado (CO) since the 1950’s. Colorado was a good place to evaluate Cercospora, since that region had few other leaf spots. The region experienced housing development and limits on irrigation water, making it hard to keep the nursery in Colorado. In 2006, the Cercospora nursery was moved to Michigan (MI) where the climate is humid and water is abundant, which creates conditions for ideal development of Cercospora. However, Michigan’s climate also is conducive to the development of other leaf diseases, which has necessitated modification and optimization of techniques used to create a successful Cercospora leaf spot nursery. The Ruppel and Gaskill methods were initially used in Michigan, but now have some key changes. In MI, the Cercsopora nursery is inoculated using spore counts instead of leaf:water ratios, irrigation is applied minimally, buffer/spreader rows are placed perpendicular in the fields, and leaves collected for inoculum are selected to avoid other common leaf spots. In 2009 and 2010, the Ruppel and Gaskill methods and the MI methods were compared. In both years, the peak of the epidemic was at least 10 days earlier using the MI methods as compared to the Ruppel and Gaskill methods. A closer look at how changes to the Ruppel and Gaskill methods have improved the performance of the Cercospora leaf spot nursery, in MI, will be discussed.