Hello Steve,

Thank you for contacting University of Minnesota Extension about the soil spots that are appearing in your lawn this spring.

The surface soil with the holes that is evident in IMG_4932.jpeg looks very much like the work of field ants that are active at this time of year. However, I’m more at a loss for clues with the first two pictures. You mentioned that you did some raking so I’m wondering if that is the reason that these two pictures look different from the third. I’d like to ask you first if the spots where this is happening all look more like the third picture (IMG_4932.jpeg) before you did any raking or other clean up. Also, I’d like to ask you some more questions.

1. I see some holes in the ground in IMG 4932, have you seen them on other spots as well? Exactly how big are the holes? An 1/8 inch, 1/4 inch, 2 inches? Each diameter would indicate a different insect.
2. Before you rake, is the soil that is there fairly flat or in a mound? How high in inches and big around is a mound? Is it cone shaped or a low mound? Is there a U-shaped channel around the holes?
3. Do you see any trails or ridges in the lawn? Have you noticed any nightcrawlers in the spots?

If your answer is that there are mostly 1/8 to 1/4 inch holes, that the sites all look like that third picture, there are no trails or ridges in the lawn, I think field ants might be our best guess, especially if you see ants there.

If you go to https://extension.umn.edu/insects-infest-homes/ants#field-ant-42363 you will see both a picture of the field ant and the lawn damage they cause. If possible, use the information on this page to identify ants in these mounds.

After you have identified field ants as your pest you should decide if the damage to your lawn is intolerable, or if it can be remedied simply by reseeding those bare patches. Generally, the advice is to tolerate ant nests when possible. See https://blog-yard-garden-news.extension.umn.edu/2018/06/ants-in-turf.html.

If you do decide to treat the lawn to eliminate the field ants, restrict your treatment to the effected patches. Insecticides appear to be the only control option available for ants at this time. One key to success is to make the initial application as soon as surface activity becomes apparent. Field studies indicate that some insecticides do not kill these insects, but instead induce them to move away. However, applications made directly to the mound enhance the effectiveness of the material. While mound directed applications take longer to complete, they reduce the amount of pesticide used and the likelihood of misapplication.

Look for an insecticide labeled for ants in turf. Granular insecticides are the most effective. Common active ingredients include bifenthrin, B-cyfluthrin, permethrin, and orthoboric acid. Some of these products may need to be watered in after application. Most importantly, if you use an insecticide, follow all label directions very carefully for both amount and method of application. It is never a good idea to over-apply an insecticide.

Be careful about raking the spots now as the ground is still soft and you might wind up tearing out grass in those spots.

Hope this helps! If you can’t find any ants and you see more damage to your lawn let us know.

Ed C, Ramsey County Master Gardener

Hello Steve,

Thank you for getting back to us with more information. Based on your responses I don’t think we can positively identify the pest as an insect, mole, or vole. Scat is a possibility. You can see pictures of different animal scats at https://sites.wustl.edu/monh/missouri-scat-identification/, or https://files.dnr.state.mn.us/mcvmagazine/young_naturalists/young-naturalists-article/scat/janfeb2019_young_naturalists.pdf. I believe you said these were evident after snow melt so the shape of the scat may be somewhat obscured to identify. Black Bear or Raccoon are possibilities. In any case, be very careful cleaning it up. 

Observe scat from a distance. Avoid handling any droppings without proper personal protection. Avoid inhaling around scat. Some diseases may be contracted through dust-borne particles, so stay upwind if outdoors. Raccoon roundworms (Baylisascaris procyonis) live in the intestines of raccoons. The roundworm lays upwards of 100,000 eggs each day which are shed through the raccoon’s feces (scat). 

My suggestion is to pick it up, keeping in mind the above precautions, and to keep an eye out for fresh specimens or tracks in your yard. If you see a bear you can report the sighting to the MN DNR at https://www.dnr.state.mn.us/hunting/bear/bear-sightings.html.

You can patch your lawn now if you do it very soon, otherwise wait until late August or early September. Assuming you just want to patch a few holes and not renovate your lawn I would recommend getting seed from a local nursery rather than a big box store. Low cost seed mixes often contain low quality or annual grasses that won’t return the following year. It also depends if you have a low maintenance lawn that you just mow and fertilize very occasionally or if you have a higher maintenance lawn. For most MN lawns a mix of Bluegrass and Fine Fescues works best. Depending on how much sun is on the lawn and your maintenance level you can find specific recommendations on seed selection and planting at https://extension.umn.edu/lawn-care/renovating-lawn-quality-and-sustainability#seed.

Good luck in identifying the culprit who is leaving those deposits in your yard. Let us know if we can be of further help.

Ed C, Ramsey County Master Gardener