Gaeumannomyces graminis f.sp. avenae
Take all patch is an important disease on bentgrass, particularly newly established stands of creeping bentgrass turf. The disease first appears in late spring or early summer, as a patch of bronze or bleached turf. The center of the patch eventually dies and is can give rise to weeds, particularly annual bluegrass. Spots range from 4-6 in. (10-15 cm) in diameter at first, but may grow into large patches, several feet in diameter over a period of years. Plants affected have shallow root systems, and are easily pulled out of the ground. Black runner hyphae of the fungus can be observed on crowns and roots microscopically.
The pathogen can survive on thatch and dead tissue as dormant mycelium. The fungus attacks crown and root tissues of the plant during the cool, wet weather of the spring and fall. It is most severe on newly established creeping bentgrass turfs. Development can be favored by applications of lime and by high soil pH.