Dealing with Them
Underneath the casting mounds, dew worms’ extensive tunnels can dip several meters below the surface. This inaccessibility, combined with their creepy size, makes them very hard to kill.
If you won’t be satisfied until every one of them is dead, you have a frustrating road ahead. My recommendation is to focus on controlling their numbers, and the damage they do, by keeping them underground. They’re also highly mobile and tend to populate blocks of houses at a time, often in older neighborhoods, so if you use chemicals to eliminate them, you are really only created a vacuum and encouraging others to move in. If you use cultural, preventative controls, you will make your yard less appealing on the long run.
Aerate your lawn in the spring and fall, and rake it out well. This will reduce the thatch and make the surface less appealing to worms overall. There are many companies offering the service or you can simply rent an aerator.
Don’t water your lawn in the evening, and only water it when needed. In a normal rainfall year, a healthy lawn actually needs little or no supplemental watering. If your lawn is patchy, top dress with fresh grass seed or, if it’s very unhealthy, consider tearing it up and starting again with fresh turf.
If you insist on using chemicals, the active ingredient carbaryl is approved for use against dew worms. Most products containing carbaryl have, wisely, been banned, and the last product with it is called Sevin. Sevin will reduce your dew worm numbers, but even it won’t eliminate them. It is definitely not safe for animals, children, or pregnant women.
