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Night Crawlers Can Cause Lawn Problems

The too many night crawlers point is reached when their castings make the surface of the lawn too rough or difficult to walk over or contribute to an unsightly looking lawn surface.

A modest population of night crawlers can be beneficial to a lawn because they aerate, digest excess thatch and contribute to the nutrient balance of the root zone with their waste discharge.

“However, too many night crawlers can prove to be a problem,” says Ron Smith, North Dakota State University Extension Service horticulturist. “The ‘too many’ point is reached when their castings make the surface of the lawn too rough or difficult to walk over or contribute to an unsightly looking lawn surface.”

Smith has some steps to follow to reduce night crawler numbers to a tolerable or unnoticeable level:

Step 1. Once the grass has greened completely, rent a power rake and run it over your lawn in two directions that are perpendicular to each other. Be sure the tines are set low enough to break up or remove the castings.

Step 2. Either deeply water your lawn or wait until after a heavy rainfall event that will soak the root and soil profile completely. At least the top 3 inches of soil should be saturated.

Step 3. Treat your lawn for grubs with liquid carbaryl (Sevin), following label directions carefully. For best results, this should be applied going into the evening hours because the worms tend to come to the surface during the cooler hours of the night. Try to time this application when no rain is forecasted for up to three days. Do not water your lawn during this interval.

Step 4. Wait at least two weeks to look for new castings to appear. If they do, repeat the insecticide application procedure.

While not on the label, the carbaryl effectively will lower the population of night crawlers, as well as any grub or sod worm population that might have been harbored in your lawn.

“Often their population will rebuild to the point of annoyance by midsummer,” Smith says. “If that is the case, wait until the ground is softened by a good rain or an irrigation event and then rent a ballast roller to flatten the mounds.”

Smith advises repeating the treatment again next spring.


NDSU Agriculture Communication – April 28, 2011

Source:Ron Smith, (701) 231-7123, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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