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ARS Home » Midwest Area » East Lansing, Michigan » Sugarbeet and Bean Research » Research » Publications at this Location » Publication #433293
Research Project: Sugar Beet Genetics and Pathogen Interactions

Location: Sugarbeet and Bean Research

Title: Cercospora leafspot screening nursery, 2025

Author
item Hanson, Linda
item Goodwill, Thomas
item CORDER, HOLLY - Michigan State University

Submitted to: Review / Technical Review
Publication Type: Research Technical Update
Publication Acceptance Date: 2/5/2026
Publication Date: 3/9/2026
Citation: Hanson, L.E., Goodwill, T.R., Corder, H. 2026. Cercospora leafspot screening nursery, 2025. Review / Technical Review. in Research Results 2025. Michigan Sugarbeet REACh. Bay City, MI. Pgs 43-44.

Interpretive Summary:

Technical Abstract: Cercospora leaf spot is the most damaging foliar disease of sugar beet in the United States. A joint disease nursery has been run between the USDA-ARS, Michigan State University, and the Beet Sugar Development Foundation to screen breeding lines and commercial varieties for response to this disease. The nursery is set up as a randomized complete block design with four replications at the Saginaw Valley Research and Education Center near Frankenmuth, MI. Seed were planted April 30 in 2025. An inoculation with a liquid spore suspension of Cercospora beticola, the causal agent of Cercospora leaf spot, was applied July 1. Spores ere obtained from symptomatic leaves collected form the 2024 nursery, making sure to avoid collecting leaves from materials with reported single gene resistance. The first Cercospora leaf spots were observed in the field on June 26, before the inoculation took place. First symptoms were observed on a table beet variety, supporting the high susceptibility of this material. Disease ratings were started on July 30 when susceptible control beets were observed with multiple spots on the leaves. Weekly ratings continued through August 20 when growth of new leaves started to reduce severity ratings. Plots were rated using a 0 to 10 scale where 0 is no spots and 10 is complete defoliation. On the final rating date, average Cercospora ratings across the nursery ranged from a low of 4.3 to a high of 6.8 among commercial varieties. The highly resistant variety, showed more severe disease than in earlier years. In 2023, this variety had an average severity of 3.9 at the final rating on Septermber 8, while it had a rating of 4.8 on August 20 in 2025 and was not significantly different from a resistant variety without the single-gene resistance. This agrees with reports from growers of loss of efficacy of the single gene resistance. The plots also were rated for natural Alternaria leaf spot as this has been a pathogen if increased concern in the region. No The varieties were rated twice using a 0 to 5 ratings scale where 0 is no Alternaria leaf spot and 5 is 50% or more of the leaves dead from Alternaria leaf spot. Ratings ranged from 1.0 to 3.8 at the final rating, supporting differences in host resistance, although some varieties could not be rated due to damage from Cercospora leaf spot.