Controlling Earthworm Casts

Earthworm casts can be a big nuisance this time of year.  These worm casts have negative effects on the playability and the overall aesthetics of the turf.  They also affect the quality of cut if not removed directly ahead of the mowers.  The earthworms are active all season long, but the casts they leave behind are more noticeable in the fall for a couple of reasons.  First off, it seems as though the soft moist soil this time of year is ideal for them to tunnel in and out of, compared to the hard compacted soils of summer.  More tunnels = more casts on the surface.  Second, our mowing frequency is reduced this time of year due to slower growth rates and reduced staffing levels.  Less mowing = more casts on the surface.

earthworm casts affect ball roll, aesthetics and mowing quality

Interestingly though, there are other forces at work that seem to be contributing to the excessive worm casts.  A recent USGA Green Section Record publication has shed some light on this issue and here is a quote from that article:

"During the past 20 years, however, the problem of excessive earthworm castings interfering with play on golf courses has become more serious and widespread.  Why?  Residues of old, highly persistent chemicals like chlordane, banned many years, are finally dissipating from soils and no longer suppressing earthworms.  Earthworm-toxic soil insecticides, like diazinon, bendiocarb, and carbaryl, have been replaced by chemistries that are more selective."

We have recently completed a trial using an organic fertilizer to control earthworms.  This fertilizer named Early Bird (I know, brilliant marketing) has provided us with excellent control of the earthworms resulting in an extremely significant reduction in worm casts.  We are going to be treating all the tees this week and will continue to monitor the earthworm activity to see exactly how long we can achieve results with each application.  Early Bird also provides nutrition to the turf while controlling the earthworms.

For further information, you can read the USGA Green Section Article in its entirety here: Controlling Earthworm Casts on Golf Courses