Crayfish or crawfish chimneys can make the landscape look unsightly in areas where water saturates the ground. In addition, chimneys cause problems for the homeowner when trying to mow the lawn. Running into them with lawn equipment causes troubles, such as dulling the lawnmower blade and could send chunks of mud flying, which could lead to injury.
Crayfish chimneys can make the landscape look unsightly in wet, saturated soils.
Barbara H. Smith, ©2023 HGIC, Clemson University
What is a Crawfish Chimney
They usually appear in the spring and are generally found in wet areas of the landscape. The male crawfish creates a chimney from mud excavated by creating tunnels below the ground. This smokestack-looking mound is critical to the survival of the crawfish. The male crawfish usually makes two chimneys for escape reasons, and these chimneys lead to a vast number of tunnels below ground where female crawfish reside with their young. These tunnels can be three or four feet long, extending in multiple directions. The end of each tunnel is usually underwater. This area is essential for the survival of the female and their young.
It is striking how the crawfish create these tunnels using their legs and mouth parts to carry the mud. They roll the mud into small pellets, out of the tunnels and to the surface, where they stack and create the chimneys. One unique feature of the chimney is that it may be different colors, which is determined by the different layers of soil the crawfish moves through to create the tunnels.
Why Do Chimney Tunnels Exist
There are many theories on why the chimney exist. The simplest is that the crawfish never want to leave the burrow due to predation; therefore, they stack the mud outside the tunnel instead of carrying it away. They rarely leave the tunnel and retreat into the tunnel if approached while aboveground. Another reason might be to get airflow through the tunnels. The female crawfish rely on the water to be oxygenated so they can breathe. The airflow in the tunnels helps raise the interior humidity and aerates the water necessary for the crawfish’s survival. If the water becomes low in oxygen, the crawfish and the young can still breathe through their gills. During drought conditions, they can plug the tunnel to keep the remaining water in the tunnels for the rest of the crawfish to survive. Plugging the tunnel also conserves heat, which will help the crawfish remain warm.
Control In the Yard
Unfortunately, no chemicals are labeled to control crawfish. Many home remedies are mentioned online, but these remedies are not approved by the US Environmental Protection Act. Be aware that using any chemical (or home remedy) not labeled for controlling crawfish can cause contamination of the water, the environment, animals, and humans.
Cultural control methods can be used to prevent crawfish chimneys. Start by improving the soil drainage to lower the water table. If that is not feasible, consider replacing the lawn with native plant species to tolerate damp or wet areas. For more information, see The Pesky Wet Spot in Your Lawn.
In the short term, to prevent damaging equipment, knock down the chimneys and break them up before performing any lawn maintenance.
Originally published 4/23
