Control of Taraxacum officinale (dandelion) and other broadleaf weeds in turfgrass has been readily achieved with phenoxy herbicides, but the herbicide option has been revoked in many regions, necessitating alternative weed control strategies. One biological alternative is Sclerotinia minor, an Ascomycete fungus. The impact of S. minor on broadleaf weed dynamics and biotic interactions were studied in a turfgrass environment. The goal was to maximize effectiveness of a S. minor formulation as a biocontrol of dandelion using an ecological approach. S. minor efficacy was not affected by turf microenvironments and was similarly efficacious with spring or fall application. All accessions from a worldwide collection of dandelion and 32 turfgrass broadleaf species were susceptible to S. minor. Biocontrol efficacy was inversely correlated with dandelion age, but efficacy on all ages was enhanced in the presence of grass competition. When combined with regular mowing at 7-10 cm, the S. minor suppressive effect on dandelion was similar to the herbicide effect, particularly in the following season. Weed suppression was less with close mowing at 3-5 cm due to increased dandelion seedling recruitment. While spring herbicide application was effective to suppress dandelion population, the S. minor treatment has no residual activity, necessitating a second application to suppress seedling recruits. Root regrowth after S. minor infection was minimal and was further reduced in superior quality turf after season-long mowing, and after spring applications. S. minor infected dandelion seeds, reduced the dandelion seedbank, and reduced dandelion seedling emergence by 98%. S. minor did not affect the emergence or the total biomass of cool season temperate turfgrass species. Turfgrass quality was improved following S. minor application and populations of other broadleaf weeds were also controlled by S. minor. Understanding the biotic interactions within the turfgrass environment has rewardingly lead to successful integration of the S.minor biocontrol with the common management tools of mowing and over-seeding to achieve excellent control of dandelion and a healthy thriving turf.

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