Does Sulfur Kill Nightcrawler Worms in a Lawn?

Earthworms, Sulfur and Soil pH Levels

• Earthworms feed on organic matter and soil, grinding it in their gizzard and expelling the waste -- called casting -- in a bumpy line on the surface of lawns. Earthworms don’t tolerate acidic soils with a pH level of 6.0 or below. Adding sulfur to the lawn will lower the pH level of alkaline soil, making it acid, which reduces earthworm activity and drives them into other areas. According to the Michigan State University website, a soil pH level of 5.8 or lower will drive away most species of earthworms.

Benefits of Earthworms

• Nightcrawlers aerate the soil by tunneling and burrowing through the ground, which can be more effective than aerating equipment, according to the Colorado State University Extension website. Their tunneling and burrowing allows water and oxygen to enter the soil and reach the root zone of the turfgrass easily. Nightcrawlers also help decompose grass clippings and thatch buildup. This natural recycling process increases organic matter and nutrients in your lawn’s soil.

Applying Sulfur to Repel Earthworms

• Elemental sulfur is available in granular and pelletized form, and you apply it to the lawn with a broadcast or rotary spreader. The amount of sulfur needed to drive earthworms out of your lawn varies depending on the current pH level of your soil. For example, if your pH level is currently 7.0 and you want to lower it to 5.5, you will need to apply 3.5 pounds of elemental sulfur per 100 square feet. You must test the soil before applying the sulfur and after to ensure you are using the correct amount. Furthermore, always the follow the directions on the specific brand and type of sulfur you are using.

Considerations

• Adding sulfur to a lawn to change the pH level of the soil can have an adverse effect on plants that cannot handle acidic soils. Thankfully, there are other ways you can repel earthworms from your lawn without the use of chemicals. This includes allowing the top few inches of the soil to dry between watering since earthworms prefer moist soil. However, consider the beneficial aspects of earthworms and weigh the positive and negative aspects of these harmless worms before taking action against them.