Earthworms – Thousands of Casting Mounds
Q: Last year I had a beautiful lawn but now I fear I’m losing it. There are thousands of small mounds of soil similar to ant hills but much smaller. This condition covers the entire lawn area. Can you tell me what might be the cause and what to do?
A: I think the problem is caused by earthworms. You didn’t mention if there was a recent rain or irrigation but earthworms are the only organism that could push up that much dirt at once.
I also see some larger holes that might indicate raccoons.
Worms deposit soil on the surface by ingesting it, extracting the nutrients and defecating it outside their burrow. When lots of earthworms go to work at once, the result is what you see in your lawn.
On the good side, your soil has been thoroughly aerated, so water, oxygen and nutrients penetrate deeper than they would without the worms’ work.