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Key Takeaways

  • Earthworms are beneficial for soil, but they occasionally create challenges for golf course maintenance and playability when populations become high.
  • Delaying mowing a few hours so that the casts have more time to dry and dragging the fairways prior to mowing can help reduce cast issues.
  • Amending the soil with sand helps the casts dry faster but earthworm issues are generally not a primary reason to initiate a fairway topdressing program given the financial and time commitments involved.
  • There are no commercially registered pesticides labeled for controlling earthworms, but some turf care products used to control other pest issues can provide some ancillary benefit when it comes to combating cast problems.
  • Besides offering plant nutrition, fertilizers that include a saponins can irritate earthworms and bring them to the surface where they can be cleaned up.

When the average person pictures a healthy soil in their mind, they probably have an image of a loose, dark-colored soil that is somewhat moist and filled with earthworms. Just Google “healthy soil” and you’ll be presented with countless photos of people holding that exact thing. Many people associate earthworms with soil health, and for good reason. Earthworms are beneficial for soil aeration, water infiltration, thatch control, nutrient recycling and they can increase microbial activity. They are truly movers and shakers when it comes to soils.

There are over 7,000 different species of earthworms which are divided into more than 700 genera and 23 families (Edwards, 2021). Only a small fraction of that total is native to North America. Most of the earthworms that dominate our soils here in the U.S. were introduced from Europe and Asia. Lumbricus rubellus, the red earthworm, is a familiar sight in many American gardens, but it’s actually an earthworm from Europe that was most likely introduced via soil from early settlers.

Native and non-native earthworms can be found in soils throughout the United States, including on golf courses, where the perennial crop of turfgrass organic matter provides a continuous food source for hungry earthworms. Many spend their time at or near the surface feeding and reproducing. Occasionally, this activity creates challenges for golf course maintenance and playability when earthworm populations become high.

As earthworms feed on the soil particles, they can create mounds of excrement which are referred to as casts or castings. Most of the time these casts go unnoticed. However, when they appear on finely manicured turf such as putting greens, fairways and tees, they can become quite a headache, especially in high numbers. The casts are unsightly and can interfere with play. They can also disrupt turf maintenance equipment. In some instances, the amount of soil that is brought up to the turf surface by earthworms looks like core aeration. Trying to mow over moist casts results in quite a mess and the rollers could become caked with enough material that you have to stop cutting.

When it comes to dragging and busting casts there are many options. Golf courses use everything from a specialized steel mat to an old section of chain-link fence. I have also seen some success with brushes, weighted ropes and watering hoses. Again, the longer you can wait for the casts to dry the better the results.

If you prefer to be less reactive and more proactive, there are some additional strategies that can be implemented to reduce the prevalence of nuisance earthworms. The first is to amend the soil with sand so that any casts that are brought to the turf surface are easier to clean up. Whether sand creates a less favorable environment for earthworms or simply helps the casts dry faster, golf courses that topdress their fairways tend to have less problems with casts. Now, implementing a fairway topdressing program is not something that should be done without careful consideration given the financial and time commitment involved. Overcoming earthworm issues is generally not the primary reason to initiate course-wide fairway topdressing, but it is often an added benefit. A USGA Course Consulting Service visit can help determine if fairway topdressing makes sense for your golf course.

Another technique that some golf course superintendents implement to reduce high earthworm counts is to mechanically control them using specialized linear aeration equipment. The Redexim Verti-Quake, Imants Shockwave and Sisis Multislit are three PTO-driven implements that cut several inches into the soil profile. The numerous blades help to alleviate soil compaction and can reduce the number of earthworms living near the surface. The overall effectiveness of this approach has not been researched extensively but anecdotal reports from the field indicate that it can provide some relief. However, the duration of control is likely to be limited given the ability of earthworms to regenerate and the fact that earthworm eggs can hatch in just two to three weeks’ time.

Golf courses that routinely struggle with nuisance earthworms are often eager to apply a product that can eliminate their activity near the surface. Unfortunately, there are no commercially registered pesticides that are labeled for controlling earthworms. Having said that, there are certainly some available turf care products that are used to control other pest issues which can provide some ancillary benefit when it comes to combating earthworm cast problems. Insecticides such as carbaryl, chlorpyrifos, clothianidin, bifenthrin and imidacloprid have been shown to be toxic to earthworms, as has the fungicide thiophanate-methyl (Boyle et al., 2019). If you are using any of these products to protect against insect and disease damage, you might also decrease earthworm activity as well.

Arguably the most effective control option for limiting earthworm casts are saponins. These naturally occurring soaps and surfactants are present in the leaves and seeds of all kinds of plants – including asparagus, beans, peanuts, chickpeas, sugar beet, tomatoes and tea (Oleszek and Oleszek, 2020). During the 1890s, a British greenkeeper by the name of Peter W. Lees applied mowrah meal, a meal made from seeds of Bassia latifolia, for earthworm suppression (Potter et al., 2011). Saponins within the mowrah meal irritated the earthworms and brought them to the surface where they could later be cleaned up. While most of today’s turf managers probably have never heard of mowrah meal, many have heard of Early Bird Natural Organic Fertilizer. Besides offering plant nutrition, this product included a saponin-containing tea seed meal component. Golf courses that used it as part of their fertility program could expect less earthworm cast issues. Unfortunately, the product is no longer in production. You might be able to find some alternatives that include saponins like Rhizo Aide from Grigg or Tea Seed Meal from Planet Turf.

Future earthworm control measures are also being investigated. A new company called Lisi Global has developed a machine that generates high-voltage pulses to target soil-borne pests. Their apparatus, which they call Direct Turf, temporarily places electrodes into the upper few inches of the soil and electrocutes target pests. It has been shown to be effective at reducing populations of nematodes and the oomycete pathogen Phytophthora cinnamomic (Riga et al., 2020). The machine will be evaluated in future research work at Penn State as a chemical-free solution for nuisance earthworm populations. Preliminary test results look promising.


Earthworms increase soil health. Moderate levels of earthworm activity in golf course soils can actually be beneficial for helping to decompose plant material and accelerate nutrient recycling. It is only the casts on the surface that are detrimental to course maintenance and playability.

A certain amount of patience and understanding by turf managers and golfers is critical. We cannot expect to completely rid golf course surfaces of any signs of earthworm activity and must learn to live with these tiny creatures. Often, the best approach is to simply break up the casts and drag them back into the turf canopy. Those who deal with cast issues for more than a couple of isolated times per year might need to implement some additional measures. As always, make sure to fully read and understand any pesticide and fertilizer labels and apply them in accordance with the directions.


Boyle, P. E., M.D. Richardson, M.C. Savin, D.E. Karcher, and D.A. Potter. 2019. Ecology and management of earthworm casting on sports turf. Pest Management Science. 75(8): 2071-2078.

Edwards, C. A. 2021. The living soil: earthworms. Natural Resources Conservation Site. USDA.

Oleszek, M., and W. Oleszek. 2020. Saponins in food. Springer, Singapore.

Potter, D. A., C.T. Redmond, and D.W. Williams. 2011. Controlling earthworm casts on golf courses. USGA Green Section Record. October 21. 49(41): 1-4.

Riga, E., J.D. Crisp, G.J. McComb, J.E. Weiland, and I.A. Zasada. 2020. Directed energy system technology for the control of soilborne fungal pathogens and plant‐parasitic nematodes. Pest Management Science. 76(6): 2072-2078.