Skip to main content
ARS Home » Midwest Area » St. Paul, Minnesota » Plant Science Research » Research » Publications at this Location » Publication #224616

Title: Effect of glyphosate on foliar diseases in Roundup Ready alfalfa

item Samac, Deborah - Debby

Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/1/2008
Publication Date: 7/26/2008
Citation: Foster-Hartnett, D., Samac, D.A. 2008. Effect of glyphosate on foliar diseases in Roundup Ready alfalfa [abstract]. Phytopathology. 98:S54.

Interpretive Summary:

Technical Abstract: Foliar diseases are a serious problem for alfalfa management in all areas where alfalfa is grown. Defoliation due to foliar diseases varies from 3-71% depending on time of year, environmental conditions, and locale. Fungicide treatments are cost-effective in only some years and locations. Recently, glyphosate was shown to be effective in reducing rust diseases in glyphosate-resistant wheat and soybean. Glyphosate inhibits 5-enol-pyruvyl shikimate 3-phophate synthase (EPSPS), an enzyme found in plants, fungi, and bacteria. Plants engineered for glyphosate resistance with a glyphosate-insensitive EPSPS take up and translocate the herbicide throughout the plant. In greenhouse experiments we found that application of glyphosate at the lowest recommended field application rate completely controls alfalfa rust (Uromyces striatus) on 90% of 4-week-old seedlings when plants are inoculated with the fungus 3 days after glyphosate treatment. In addition, excellent control of rust was obtained when glyphosate was applied 4 days after rust spores, indicating that the herbicide has protective and curative activity. Protection of plants from powdery mildew (Erysiphe pisi) was also observed. Preliminary experiments suggest glyphosate treatment reduces seedling death due to anthracnose (Colletotrichum trifolii). These results indicate that glyphosate could be used to help manage foliar diseases in Roundup Ready alfalfa.