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You get the picture. There are a couple of surface sports turf pests that can create havoc with playing conditions. Two of those pests are earthworms and moles and they are directly influenced by each other.

Benefits of earthworms are numerous. Most importantly, they recycle nutrients and improve soil structure. In some scientific circles, earthworms are seen as a barometer for soil health. As such, we would be loathe to suggest that sports turf managers go on a mission to eradicate earthworms from playing fields.

Disadvantages of Earthworms - Surface Castings and Feeding Moles

Some earthworms, specifically the large European night crawlers, produce "casts" (nutrient rich fecal matter) on the field surface (picture left). Castings interfere with the playing surface, making it unstable and slippery. Castings can also become sites of weed seed germination.

In addition to the castings, earthworms attract problem pests such as moles, particularly if the playing field or outfield is next to woodland. Moles eat white grubs but earthworms are the staple of a moles diet. Using insecticides to control white grubs as a method of getting rid of moles can actually back-fire, as moles have been seen to dig further and cause more damage to get a sufficient feed of earthworms once the white grubs have gone. The best method of controlling problem moles on athletic fields is to set traps.

Adaptation:

Earthworms live in non-compacted, moist soils where there is an organic food supply. They also prefer to live in a slightly neutral/alkaline soil pH and are not tolerant of soil pH lower than 5.0. Knowing what kind of environment attracts earthworms can help turf managers control their populations somewhat.

Control Options

* Limit their food supply: reduce thatch levels, remove clippings (particularly at those times of the year the earthworms are most active), and limit the use of organic fertilizers

*Strive to keep soil pH slightly acid. Use acidifying fertilizers (e.g. ammonium sulphate), and do not apply lime. Applications of lime significantly increase earthworm populations

*Investigate topdressing with abrasive aggregates. Researchers have looked at using abrasive materials like angular sand as a way of limiting earthworm activity. Generally, topdressing appears to have a positive effect following application but it is not a long term control option. Dr. Williamson from the University of Wisconsin has been looking at abrasive topdressing materials to control earthworm populations. His treatments included "Black Jack" - a byproduct of the coal industry, Zeolite, and a mustard seed product. These were compared to a soap treatment, hydroject, and two pesticides (thiophanate-methyl and carbaryl). Interestingly, the Black Jack and Zeolite showed similar control to the pesticides. He did raise concern however, about the abrasive nature of the Black Jack and what kind of damage that product may do to turf stems and roots.

*Chemical control to suppress populations. Earthworms are considered beneficial organisms, so there are no chemicals specifically labeled for their control. In fact since most of our currently available insecticides and fungicides have been specifically selected because of their benign affects on earthworms, earthworm castings on highly maintained turf is increasing. The fungicide thiophanate methyl (Clearys 3336) and insecticide carbaryl (Sevin) are two products that have shown efficacy on reducing earthworm populations.

References/Further Reading:

Baker, S. (1997) Earthworms and casting control. STRI Turfgrass Bulletin, Issue 195

Williamson, C.R. (2004) Managing earthworm castings; can topdressing discourage earthworms over the long term? Golf Course Management, Issue 93

Ohioline Factsheet: Effective Mole Control

Posted by Pam Sherratt & Dr. Dave Shetlar