The earthworm, Lumbricus terrestris, is the major culprit that produces castings. However, other worms like the "pinworm" may cause castings on greens around the country. The photograph to the left shows earthworm casting caused by the pinworm type earthworm on a bermudagrass green in Hawaii (provided by Jon Scott). According to Lee (1985) the most critical soil properties that affect earthworm activity include food supply (organic matter, grass clippings), moisture (needed), temperature (cool), texture (greatest on light and medium loams with smaller populations on heavy clays and course sand), and pH (acid soils not favorable for earthworms).

If you look at these cultural practices such as clipping removal, thatch control, sand topdressing, and lowering pH might be practices to discourage casting formation. I am not sure how effective these practices are except to mention that clipping removal and thatch control would probably be of minor success, sand topdressing on fairways as a regular basis might not be practical nor proven effective. Regarding the lowering of pH, sulfur applications may help acidify the surface layer helping to discourage earthworm activity.

Some have suggested that some sort of water injection (ex. Toro Hydroject ®) would blast them and reduce the numbers. Again, I do not know how effective this would be given that Lumbricus terrestris tunnels fairly deeply into the soil profile. In other situations, like the one shown to the left, the symptoms or the castings are reduced on the green by poling prior to mowing

There are some products on the market that may help reduce the level of earthworm activity. Many of these products are angular shaped materials that are applied as topdressing. Research has shown that angular shaped particles agitate earthworms.