Earthworms are an indication of healthy soil and help break down organic matter and recycle it into the soil, spreading nutrients and encouraging microbial activity. They also help improve soil porosity with their burrowing and tunneling, which allows for better water and air movement. Despite their good work under the surface, they occasionally cause headaches for golfers and superintendents with messy worm castings on closely mown turf.
For many years, fungicides and other products were used with the knowledge that an application for other pests and diseases would also have a secondary effect of pushing earthworms deeper into the soil to minimize their surface impact. Now, we see the rise in usage of newer products that utilize tea seed extracts rich in saponin as active ingredients. These products are not pesticides but rather help bring worms to the surface where they can be relocated or removed with various methods.
Two big considerations when using these products are timing and quantity. Timing a tea seed extract or saponin-based fertilizer application with rainy spring or fall weather can work well since these products need to be watered in. A large number of worms on the surface is also messy, so timing treatments to avoid peak golf activity is beneficial.
We love worms and the dirty work they do, but we love them more the farther away from high-impact areas they are. There are a number of tea seed extract and saponin products currently on the market and available in all states. Conducting a small trial to check results and plan cleanup is always a good idea before implementing a course-wide program. If you’d like a deeper dive on the topic, check out the Green Section Record article “Managing Earthworm Casts on Golf Courses.”
West Region Agronomists:
Brian Whitlark, regional director, West Region – bwhitlark@usga.org
Ross Niewola, agronomist - rniewola@usga.org
Information on the USGA’s Course Consulting Service
Contact the Green Section Staff