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Description
Alfalfa is the fourth most valuable crop in the United States and is widely grown as feed for livestock due to its high protein content. In 2021, South Dakota harvested 1,320,000 acres of alfalfa and has some of the most acres growing in the United States. Alfalfa seedlings are highly susceptible to disease, which reduces field establishment and yield. Oomycete pathogens, Aphanomyces euteiches and Pythium sp., have devastating effects on newly seeded alfalfa fields causing seed rot and reduced root development. Current management strategies are fungicidal seed coatings and planting disease resistant alfalfa varieties. To create more of an Integrated management strategy, we investigated numerous commercial, organic biological control (biocontrol) treatments, which had previously shown to be effective against oomycetes but have not been tested against alfalfa pathogens. South Dakota and USDA isolates of both A. euteiches and Pythium sp. were evaluated against biocontrols with active ingredients such as: Streptomyces octinobacterium K61 (Mycostop), Bacillus amyloliquefaciens D747 (Southern Ag), Streptomyces lydicus WYEC 108 (Actinovate), and Bacillus subtilis QST 713 (Serenade). Biocontrol activity against A. euteiches and Pythium sp. was evaluated in growth chamber assays using seed of a susceptible alfalfa variety, Saranac. Treatment effectiveness against A. euteiches was assessed by rating seedling roots after 29 days using a standardized rating scale. Seedlings inoculated with Pythium sp. were evaluated after 5 days to calculate percent germination. Biocontrols with the active ingredient, B. amyloliquefaciens D747 have antagonistic effects against Pythium sp. increasing percent germination by up to 71%. 5. octlnobacterium K61 had high activity against several isolates of A. euteiches. Various biological control agents demonstrated activity against alfalfa pathogens, which provides growers with an additional management strategy to protect their fields. In Fall 2022, we plan on testing A. euteiches and Pythium sp. isolates against biocontrol treatments that use fungal antagonists.
Publication Date
2022
Recommended Citation
Rebstock, Travis R.; Tordsen, Conner L.; Daniels, Brandon; Rachynska, Oleksandra; and Sathoff, Andrew E., "Managing South Dakota Alfalfa Diseases with Commercial Biological Control Agents" (2022). Annual Research Symposium. 42.
https://scholar.dsu.edu/research-symposium/42