|DUNG, JEREMIAH - Oregon State University|
|KAUR, NAVNEET - Oregon State University|
|WALENTA, DARRIN - Oregon State University|
|FROST, KENNETH - Oregon State University|
|HAMM, PHILIP - Oregon State University|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/22/2017
Publication Date: 1/4/2018
Citation: Dung, J.K., Kaur, N., Walenta, D.L., Alderman, S.C., Frost, K.E., Hamm, P.B. 2018. Reducing Claviceps purpurea Sclerotia germination using soil-applied fungicides. Crop Protection. 106:146-149.
Interpretive Summary: Ergot is a floral disease of grasses that causes significant yield reductions in grasses grown for seed. Because fungicide sprays do not always provide adequate control, studies were conducted to determine if fungicides applied postharvest could reduce the inoculum potential from the overwintering propagules (sclerotia) of the pathogen on the soil surface. Results from this study indicated as much as 73% reduction in potential spore production, which is highly significant in that it provides a new approach for ergot control.
Technical Abstract: Ergot, caused by the fungus Claviceps purpurea, is an important seed replacement disease of perennial ryegrass grown for seed in the U.S. Pacific Northwest. Current management efforts rely on multiple fungicide applications to protect flowers from airborne ascospores during anthesis, but protective fungicide applications often provide incomplete control. Applications of fungicides to the soil, with the goal of preventing or reducing sclerotia germination, can potentially reduce the amount of ascospores and primary inoculum available in the spring. Use of fungicides applied to soil to reduce sclerotia germination were compared in both in vitro and field trials In a repeated in vitro assay, several fungicides were identified that significantly reduced sclerotia germination under laboratory conditions. Azoxystrobin + propiconazole and picoxystrobin + cyproconazole reduced sclerotia germination and capitula formation in both laboratory trials, whereas fluopyram + prothioconazole significantly reduced sclerotia germination and capitula formation in one of two laboratory trials. Fall applications of fluopyram + prothioconazole to artificially-infested field plots reduced area under capitula production curve (AUCPC) values by 59, 72, and 73% in 2014, 2015, and 2016, respectively. Several other fungicides, including azoxystrobin, azoxystrobin + propiconazole, and pyraclostrobin, reduced AUCPC values by 34 to 42% over three years of field trials. These results suggest that soil-applied fungicides can significantly reduce sclerotia germination and capitula production by C. purpurea and offer the potential to disrupt the ergot disease cycle in perennial cool-season grass seed production systems.