It sounds improbable. How can one have too many earthworms? Such is the case for a property owner in Henderson County. A recent phone call led me on my first investigation to discourage earthworms, or in this case night crawlers (or 'dew worms' from a fisherman's vernacular).

The yard in question was rife with small mounds comprised of tiny lumps of castings (worm poop). This made the terrain of the yard uneven underfoot. The homeowner has been routinely rolling the yard to reduce the lumps to no avail.

Earthworms are an indicator of healthy soils, which we do have in many parts of West-Central Illinois. Controlling earthworms through pesticide applications is not an option I would consider.

Earthworms do not tolerate pH lower than 6 and applying sulfur to acidify the soil would be an option, save the fact that the lawn would then suffer.

My current recommendation is to roll the yard once more this spring, but to also follow that with a hollow-tine (core) aerator. My thoughts being that perhaps the constant rolling led to compacted soil, making surface dwelling more desirable for the earthworms.

Healthy lawn practices such as keeping the mowing height between 2-3 inches would also be beneficial.

Time will tell if the core aerator does the trick. I hope to report back with the results in the coming months.