Q: I have a photography studio and have numerous earthworm mounds on a grassy spot where I photograph families or people on the grass. My studio is on a wooded lot and this is the only piece of grass I can use for my portraits. I need to know what to do to get rid of these mounds.
A: This site recommends mustard to bring out earthworms
And this guy uses black walnuts to get his fishbait.
How to Catch Worms with Walnuts (be aware of the staining potential of walnut husks!)
You could also use the knowledge here
UGA Entomologist Paul Guillebeau says: “As long as the pesticide is labeled for use on that site, the product does not have to have earthworms on the label. If she took this action well in advance of customers, the risks to people sitting on the ground would be reduced. If I were her, I would consider placing a cloth on the ground for people to sit. It could create the impression of a picnic, and the worms would be saved, and unnecessary pesticide application would be avoided.”