The Iowa Chapter, like all the other STMA Chapters, serves as an endless source of information for any level of athletic field management in the country. Joe Wagner, past president of the Iowa Chapter, left me a message that “West Branch High School has a bumpy baseball field, they’re not members but can you give them some help; I think worms might be the problem.”


Dr. Tom Dean answered the number Joe left me, he’s a real doc with a scalpel and all.  His son played baseball so he has always been really interested in the field’s playing condition. Tom was really down with all the turf management lingo and obviously not a rookie. That conversation led to Rich Stout, Head Baseball Coach for the West Branch Bears and he made it very clear that the worms needed to go for the field to improve.


The reason for the long introduction comes from the old adage “why buy the cow if you can get the milk for free.” STMA members will bend over backwards to help anyone responsible for managing fields, but too often they don’t follow through requesting the beneficiary to join the local chapter. A membership in STMA is a great way for an athletic director to improve playing conditions while also supporting the professionalism of coaches, boosters, custodians, and grounds managers. Tapping into STMA brings with it an element of pride that pays for itself many times over.


I met the infamous Dan Devine late in his career and learned that you shouldn’t really put a price on pride, but when directed properly it has immense value that translates into tremendous profit. 


Now about those worms. In most turf situations, earthworms are a welcomed inhabitant. They decompose thatch and organic matter that recycles nutrients, tunnel macro channels in the soil for roots and drainage, reduce compaction, and distribute soil on the surface as topdressing; nature’s perfect aerification and topdressing machine all rolled into one. If they could only distribute their fecal matter casts in a thin layer rather than a moundy bump, we would give them a hug and not curse their presence and kick at their little dirt monuments.


Rich has rolled the field because there are too many bad hops and it’s simply unsafe. He commented, “That helps but the worm casts keep coming and constant rolling is too impractical. We want to kill or at least slow down the worm activity.” This is somewhat controversial since we know that worms are a wonderful and natural method of aerifying soils and reducing compaction. There are no pesticides specifically labeled for worm control since they are usually thought of as beneficial for soil productivity, despite the fact that they can make a field nearly unplayable and reduce the beneficial thatch layer that cushions the playing surface.


Carbaryl (Sevin) is a general use insecticide that can be used on athletic fields but is not labeled for control of earth worms. It is known to suppress earth worm activity for 7 to 30 days when applied at the highest labeled rate for other pests. Worms are most susceptible when applications are made at the start of casting and they are working on the surface. A good rain followed by a dewy night really gets them moving upward. Even with two or three applications during a playing season worm activity will be reduced but not eliminated. This is good because the worms can continue to provide some of the benefits mentioned earlier with less casting during the playing season.


Casting problems seem to be greatest on fields where worms have consumed all of the visible thatch/mat/biomass. If thatch is limited, try increasing nitrogen fertility by 1 to 2 pounds N 1000 sq. ft./year. This gives the wigglies more to ingest and seems to dilute the amount of visible casting. Sand topdressing also creates an abrasive layer near the surface that reduces worm activity. Sandy casts that do occur tend to crumble apart easier when mowing.


I’m all ears about your worm stories since we are researching natural products and topdressing materials to manage worm related problems on athletic fields and golf courses. Call my mobile if you have something to offer (515-231-1741) or if you know of a good fishin’ hole . . . I’ll bring the worms!


Dr. Dave Minner is a professor at Iowa State University.

SportsField Management