There are several million earthworms under every fairway. The earthworm's burrowing and feeding activity initiates thatch decomposition, stimulates microbial activity, makes certain plant nutrients more available, increases soil aeration and, in general, improves overall soil quality. Casting occurs when earthworms ingest soil and leaf tissue to extract nutrients, then emerge from their burrows to deposit the fecal matter, or casts, as mounds of soil on the turf surface. Earthworm casting on the surface of golf course fairways rapidly is becoming one of the most challenging management issues facing superintendents. It interferes with proper maintenance practices, the playability of the turfgrass and the overall appearance of the fairways.
Affected turf can become thin and the playing surface can soften.
Currently, no pesticides are registered for controlling earthworms in the U.S., which severely limits the ability of superintendents to manage this highly destructive problem. Earthworm populations can reach several million under golf-course fairways, with millions more in the roughs, unnoticed due to higher mowing heights. Unfortunately for superintendents, the basic cultural practices that produce excellent fairway surfaces also create optimal living conditions for earthworms. Earthworms feed on fairway clippings returned after mowing and on organic matter in the soil. They love the consistent, moist, fertile conditions that typically are present in fairway turf.