A fairway can become nearly unplayable if too many earthworm casting are present. These are what the small spots of "mud" are.
At Highlands CC, Earthworms can be a challenging part of fairway maintenance on several holes. While they are a sign of a healthy soil, their castings can be a headache, creating "muddy" fairways. During periods of rain the problem gets even worse. There are no pesticides labeled for earthworm control since they are such beneficial organisms. Earthworms feed primarily on organic material in soils, eating fresh and decaying material from plant roots, including turf. As they feed, they move and mix their waste with the soil in a moist, microbe-rich environment. Earthworm tunnels bring in oxygen, drain water and create space for plant roots. Their natural feeding habits mean that small amounts of soil pass through their bodies and, surprisingly, when they excrete it, it is in better condition—what goes in comes out much better!
Since we don't want to kill them, we rely on products that are known to irritate their skin, causing them to seek refuge elsewhere. One product that works really well is an organic fertilizer known as Early Bird. Unfortunately it was pulled from the market over a year ago. I did however, purchase a healthy supply of the product before that occurred.
After the fertilizer is applied, it works best if rain moves the material into the soil. To be effective, it needs about 3/4" of rain to move it to where it has to go. Anything less than that doesn't seem to work based on my experience.
This morning, this fertilizer was applied as a spot treatment to areas in the #3 fairway. If we get enough rain today, earthworms will surface by the hundreds tomorrow morning. These earthworms make great fishing bait if you're interested! Again, the fertilizer does not kill the earthworm, it irritates its skin which causes them to surface and start hiking to a new home.
About 10 years ago, we applied this product to #8 fairway, which had a huge earthworm population. It received the perfect amount of rain that evening and the next morning, there were so many earthworms at the surface, we couldn't mow the fairway. I pulled the staff from their other jobs and we spent the next 2 hours raking earthworms up and carting them off by the wheel barrow load. The earthworms were relocated to some compost piles we had at the time to the right of #13. I'll end this story by asking- do you know what a wheel barrow full of earthworms smells like?