Issue 8, June 12, 2009
The heavy rains throughout much of Illinois have created ideal conditions for crayfish to be more of a problem in turf. Crayfish have gills that require constant moisture. Rainy nights and standing water allow the migration of these insect relatives across land to new locations.
Crayfish become a nuisance in turfgrass when they burrow in high moisture soil, creating chimneys at the burrow openings. These chimneys, made of balls of clay soil that bake in the sun, become very hard. Hitting them with a mower dulls the blades and may even kill the mower's engine. The crayfish commonly emerge at night to roam about the turf. It must be common for residents of northeastern Illinois to walk barefoot on the lawn at night. I have received numerous calls over the years from that area of the state with complaints about stepping on them barefoot at night and getting their toes pinched. Occasionally, one of these roaming crayfish will crawl up on a porch and be unable to find its way out, causing consternation to the human residents and family dog the next morning.
Crayfish are 10-legged crustaceans in the order Decapoda. Lobsters, shrimp, and crabs are in the same order. Crayfish are frequently referred to as crawfish and crawdads. In northeastern Illinois, they are frequently called land crabs. Mud bug is a common name for them in the southern U.S. Crayfish have 10 legs with the front pair enlarged into chela, or pincers, at the end. The chela are used for prey capture, feeding, mating, and defense. Crayfish are scavengers, feeding on decaying organic matter, but they are also opportunistic and will capture and eat fish, worms, and other animals that they catch off guard. The other four pairs of legs are used primarily for walking and food handling.
Crayfish are elongate with the front half covered along the top and sides by a carapace. Their gills are beneath the sides of the posterior half of the carapace. The front half encloses the head and is pointed at the front. Near the front are two obvious spherical black eyes. There are two pairs of antennae. One pair is very short, whereas the other is long and obvious. The abdomen makes up the back half of the crayfish. It is elongate and made up of several segments. At the end of the abdomen is a flattened, widened telson. The underside of the abdomen has a series of elongate, paired, finger-like pleopods. A female carries her eggs under the abdomen and is referred to as being “in berry” during this time. After hatching, the young crayfish cling to the pleopods and abdomen underside for several days before dropping off to fend for themselves. Most crayfish live for three years.
Of the 21 species of crayfish that occur in Illinois, only Procambarus gracilis and Cambarus diogenes commonly occur in turf. P. gracilis is reddish brown when young but is red when adult and about 4 inches long. This crayfish occurs in turf areas and along roadside ditches. Its burrow commonly extends 6 feet or more to an enlarged chamber within the groundwater. On rainy nights, young of this species are commonly found on the turf surface. Adults occasionally occur on the surface on warm, rainy, summer nights. Reproduction occurs in open water, frequently in standing water after a rain. This species does not occur in southern Illinois.
C. diogenes can approach 5 inches when fully grown. It is reddish brown with a red carapace, although it may be green with red edging. This species lives along streams in a burrow that extends about 3 feet below the turf surface. At this point, there is usually an enlarged chamber. Another burrow runs laterally from this chamber to the nearby stream, opening below the water surface. Reproduction occurs in the stream.
Turf-living crayfish and their burrows and chimneys are numerous along streams and in low-lying areas. Golf superintendents commonly cope with crayfish by allowing these areas to revert to marsh and other wetland areas. This avoids fighting a losing battle against the crayfish and adds a different and natural hazard to the golf game. Commercial landscapes may similarly retain these areas as wetlands, occasionally mowing them at a high setting. To eliminate crayfish, the area usually must be tiled and drained. Solid wood or stone fences that fit tight against the ground have been used to reduce the migration of crayfish to fine turf areas.
Pesticides are not a factor in crayfish management. Not only are there no labeled pesticides but any chemical put into a crayfish burrow will pollute the groundwater and possibly the adjoining stream.--Phil Nixon