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We have received many queries from people concerned about mud balls appearing in their lawns? What are they? Are they in fact a cause for concern?

If your soil has a healthy population of earthworms then you may start to find small mounds of soil or mud balls on your lawn. These mud balls are the castings which have passed through the earthworms the previous night and have come to the surface as tunnels that are created below the surface of your lawn. Since they are more common in Spring and Autumn due to the optimum soil moisture and temperature for earthworms, it’s not surprising that people are reporting this issue now.

Earthworms are great in that their activity acts as a natural aeration of the soil beneath your lawn but there is also a down side to a large population inhabiting your lawn. The mud balls are quite slimy in texture as they contain soil and the natural secretions from the earthworm’s digestive system. Sitting on the surface of the grass will allow them to be smeared across the lawn during general traffic and mowing. The end result is a potentially very muddy and slippery lawn; the castings also create the perfect environment for weeds to germinate and take hold during next spring.

Lawn varieties like Sir Walter Buffalo are less susceptible to mud ball damage but earthworms can cause more issues in a Couch lawn.

At Daleys Turf, we don’t recommend using a pest control treatment to deal with earthworms, as they do a great job aerating and making the soil healthy. But there are a few ways that you can reduce their activity in a natural way.

Organic matter is a fantastic source of food for worms, so any dead and decaying matter left on the lawn will encourage them and increase their activity and therefore the amount of castings on your lawn. Rake up and remove autumn leaves that have fallen from deciduous trees and use a catcher when mowing, so that the grass clippings aren’t left on the lawn to increase the amount of organic matter and the moisture level in the soil below.

Heavier clay soils and wetter soils with an abundance of bacteria and soil flora and fauna are also encouraging to earthworms, so you can ensure that their activity is limited by having soil that is not too wet. Look at the drainage of your lawn and reduce the amount of watering in periods with consistent rainfall.

You can also rake sweep casts off the lawn using a stiff broom, rake or bamboo cane, but this option may not be very efficient should your lawn contain numerous amounts of castings. This should be undertaken when the castings are quite dry to eliminate the possibility of smearing the castings and making a giant mess of the lawn.

Just remember that earthworms are actually a sign of a healthy lawn. They help in breaking down thatch, increasing decomposition and create useable nitrogen in your soil. Five or more earthworms per square foot of soil provide your lawn with 25% of its seasonal nitrogen needs. As the moisture levels reduce the earthworms will bury deeper into the root system, just as before and you won’t even notice them continuing on with their great work during winter.

This Post Has 18 Comments

  1. Hi. I believe I have these worms on my lawn but it seems to be an unhealthy level as I have very hard lumps all over my lawn when it’s dry which become slimy, gooey mud patches when wet. I’m not sure how it got to be so many but need to find a way to reduce thevamount ifvwirm actuvity since my lawn is no longer enjoyable. Any suggestions?

    1. Sounds like you may need to incorporate some drainage to your lawn area, the worms are only trying to survive in those conditions.

  2. Can Lawn Grubs Do Something Similar? I have a blue couch lawn and an abundance of castings in an area that has lawn grub activity by the appearance of the blue/red flying waspy like inscents and colour of the lawn.

    1. I don’t believe lawn grubs do the round mud balls, it’s most likely you have lawn grubs and earthworms together.

  3. I have a lot of castings on top of my lawn in the morning and the lawn is not as green as it use to be, it looks unhealthy. What would be causing that?

    1. Hi Peter, casting on top of your lawn will be earthworms, they are coming to the surface to breathe, your soil is probably too wet or very clayish. Earthworms are great for soil however they can cause unsightly mess on your lawn. They are very hard to kill as getting the chemical into to where they live and feed is tricky.

    1. Hi Jeremy, It will depend on your lawn variety before I can answer this, but in general, how often you mow will make a difference, how sharp your mower blades are, how fast you are traveling with your mower, how often you are fertilising your lawn will all have a bearing on the finish result. Most new varieties are only green on top, and if you scalp your lawn ( mow too short) then it will turn white for a few days.

    1. Hi Betty, casting lumps this time of year suggests its too wet, however large areas dying could be unrelated to the castings, I would suggest to test for lawn grubs first.

  4. Would aerating the lawn with a fork improve the drainage? We don’t water very often and it hasn’t rained for a while but the castings are getting more numerous. I am worried the worms will spread to the lawn that is separated by a concrete path.

    1. Using a fork is a great idea to improve drainage. As well adding sand as a top dressing would also help as worms like moist soil and therefore don’t normally like sand.

      1. Informative.
        Could you tell me, if the mud balls are visible next to small ( Pinky finger) size holes.
        If not, what does make make such holes with mud balls beside them?

  5. So if they promote aeration why do lots of posts recommend to aerate mechanically? As in why would aeration need to occur when they do it themselves?

  6. Hi my entire backyard lawn has dirt clumps coming to the surface in addition the ground where this has occurred has become very spongy.. I’m hoping you can suggest a solution as it is terribly unsightly and frustratingly difficult to understand how this has occurred just recently (last 2 months). Thabks

    1. This current wet weather that is impacting the entire eastern seaboard is responsible for this problem, earthworms can’t breathe in saturated soil, so they tunnel areas out, leaving small round balls of mud. Try fertilising your lawn to have the lawn grow over these mounds, in time they will disappear with drier weather. Its a common problem at the moment.

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