I once had a lady call me inquiring how to “kill off” those pesky earthworms that had created what seemed to be a serious problem for her. Evidently every time it rained (like twice a year in Las Vegas) she had problems with the little bodies that wound up petrified on the concrete surfaces around her house. It seems that her little pooch wouldn’t go outside until all the dried up caucuses were removed. Well let me tell you, this really presented a problem for me. I was aghast that she should even think about such a thing. It was pure Vermicide! I immediately embarked on a monologue about the wonderful benefits of earthworms and how they were an important player in soil health and that she should just sweep the little guys off the sidewalk. Later, I felt bad and I did a little research and called her back with a few offerings.
Earthworms are remarkable creatures. They are likely the most recognizable (and beneficial) constituents that make up the soil fauna, in addition to insects, mites, millipedes, sow bugs, and spiders. Their numbers vary greatly depending on the soil type and environmental conditions, but it is said that good quality arable soil may contain up to 8 million earthworms per acre. That could equate to more than 1,000 pounds of red wigglers. That’s a lot of fish bait!
And earthworms do benefit the soil. As they feed on decomposing organic matter (along with the mineral soil) the fecal material is deposited as “casts.” These casts are a wonderful source of nutrients for other organisms, and the grinding action of the minerals within the digestive tract of the squiggly animals helps to produce a much healthier soil. It is said that earthworm casts may weigh as much as 16,000 pounds per acre on a cultivated field.
In addition to the improvement in soil nutrition earthwoms create a general improvement in aeration and drainage. The mixing and granulation of the soil is a process of the constant burrowing that helps to bring particles in the lower soil to the surface. The soil aggregate created is larger and more stable than before. The result is a deeper soil that drains better, has improved air exchange and fertility. What an engineering marvel.
There are many different types of earthworms (200 or more species). Some species deposit casts on the surface while others do not. The common nightcrawler appears to be the most prevalent nuisance for golf courses. Evidently this earthworm produces excessive surface casts, which can create some real headaches for golf superintendents. The casting creates less than favorable conditions with soft fairways and thin turf.
Conditions that are optimum for quality turf (and gardens) are equally favorable to earthworms. Recycled grass clippings provide a continuous food source. A regular irrigation cycle provides optimal soil moisture and helps to modify soil temperatures allowing the worms to remain closer to the soil surface.
Unfortunately pesticides can be extremely toxic to earthworms (and other soil biota). The use of insecticides and fungicides will definitely have an impact on earthworm populations. Interestingly, herbicides apparently do not have a direct impact on earthworms. Regardless, the use of pesticides should be minimal or eliminated to maintain healthy populations.
Soil pH can also have an impact on the number of earthworms. Certain fertilizers like ammonium sulfate can be toxic to earthworms. Evidently this is a result of increased acidity. The use of soil sulfur may have a similar effect.
There is some research that suggests the removal of turf clipping may aid in population decline, particularly in the spring and fall when earthworms are near the surface due to moderate temperatures.
Moreover it appears that regular and dedicated removal is one of the best control methods. Repeat harvesting (yes, the worms are used for bait) is actually a viable method for reducing populations. Bear in mind that reproduction rates for earthworms can be quite high with several hundred young each year. So the labor intensive process requires a lot of hand work.
How do you harvest earthworms? Most sources indicate that the application of an irritant is the most effective way of bringing them to the surface (just like adding rainwater to desert soils). Mustard and chlorine are two examples.
Or you could use an old technique I learned as a young boy in South Georgia. The old-timers call it “grunting” as the sound emitted was basically guttural. This method requires a wooden stake be driven into the ground, preferably with at least 12 to 18 inches in the ground and a similar length above ground. Then a portion of a concrete masonry unit (cement block) is used to rub over the top edge of the stake. A six- to eight-inch piece of a broken block is about the right length to handle. The flat portion is vigorously rubbed across the stake which creates a resounding “grunt” sound, as well as considerable vibration below ground. The worms will magically appear at the surface in a relatively short period of time depending on the soil temperature and their depth. The worms can be easily harvested by hand.
Well, like them or not, earthworms are a signal of good soil health. How you deal with them or simply tolerate them is up to you. Let’s go fishing, shall we?
Dennis Swartzell is Marketing Director for Mountain States Wholesale Nursery. He is based in Las Vegas, NV and can be reached at 800.423.6452 or via e-mail at Dennis@mswn.com.
