CALDWELL COUNTY, NC (April 9, 2018)…A common recurring question we receive at the Caldwell Extension Center is “What is making holes in my lawn or landscape?”. When mystery holes appear in the lawn, I think about the season, location, and size when formulating my answer. I actually enjoy postulating what might have caused these excavations. Mentally, I run through the list trying to match the evidence with the possibilities.
Earthworms, especially the European night crawler, can make fairly large holes in the ground. You may find 1-inch high piles of small, granular pellets of soil surrounding a pencil sized hole. These granular pellets are worm castings. These are common in spring and fall when soils are moist and temperatures are warm.
Many insects that transform from a larva to an adult in the soil leave exit holes when they emerge from the soil. I see these more in the late spring and early summer, especially after a rain. These leave a nickel-size hole. These holes may be surrounded by small mounds of loose soil and fecal pellets. The two best examples are cicadas and June beetles.
I have seen many examples of solitary bees creating holes in the lawn or landscape. These bees will make small holes in the soil. They will usually select sites where vegetation is thin. The holes they create are chambers in which their young will develop. These holes are between ¼-and ½-inch wide. There can be 100 or more solitary bees all nesting in close quarters.
Cicada killers are my favorite. They are actually a wasp. The female digs a ¾-inch hole 18 to 24 inches deep in the ground. Then she captures a cicada and drags it down the hole. She lays an egg, and her larva will feast on the cicada she has provisioned in her nest. Cicada killers prefer areas that are dry and bare or where grass is cut very short. One telltale sign for cicada killer holes is they will have all the excavated dirt mounded to one side of the hole. The wasps are also active for a few weeks during the day and are very noticeable.
Crayfish are typically the culprit when the site is wet or the water table is close to the surface. These creatures build 2 inch to 4 inch tall mud chimneys with and openings of about 1 inch in diameter. The mounded mud is very distinctive.
Voles are small rodents that do not hibernate. They are active all year long. They construct both surface runways as well as underground tunnels. They eat a variety of plants, but they especially like hostas, roses, and nandinas. Tunnel entrances are 1 to 1½ inches in diameter and no mound of soil is present.
Squirrels and chipmunks make a hole similar to voles, but squirrel holes are only about three inches deep. They bury and subsequently dig up nuts in the lawn and in mulched beds. The holes don’t have excavated dirt at the top, just like vole holes.
Damage from skunks and raccoons occurs at night. They dig holes in lawns and gardens, looking for grubs and other insects. The holes are funnel-shaped with a 3 to 4 inch opening at the top. I had a colleague tell me one time that skunks or raccoons pulled up new laid grass sod to get to insects that were beneath the new sod.
Rats may also tunnel in the soil. Rats disguise their tunnel entrances near shrubbery, wood piles, and sheds. Rat tunnel entrances can be as large as 3 inches in diameter.
Groundhogs are a pest of vegetable gardens. They will eat most anything that grows in a garden. They are active during the day. Their burrow entrance is usually 10 to 12 inches in diameter and is distinguished by a large mound of excavated dirt at the main entrance. Secondary holes will not have any mounded soil around them.
Knowing what is making holes in the lawn helps to know if control is needed. Control strategies vary, depending on what is making the holes. Cicada killers and solitary bees can be controlled with a sprinkler. They do not like wet sites. Watering encourages these beneficial insects to select another site.
If wildlife are the problem, the first reaction should be to reduce the food, water, and shelter available. This will discourage their activity. This may include controlling the grub population to reduce the food supply for skunks and raccoons.
Knowing what is causing the problem makes the solution more likely to work.
For answers to your agricultural questions, call the Caldwell County Extension Center at 828-757-1290 or visit us online anytime at http://caldwell.ces.ncsu.edu.