Released: March 24, 2005

Soil-Improving Worms Can Hinder Spring Lawn Mowing

MANHATTAN, Kan. – Some worms clearly turn in April. For lawn owners, that fact can be bad news in the short run and good in the long.

The worms are popularly known as nightcrawlers, said Ward Upham, horticulturist with Kansas State University Research and Extension.

They’re big earthworms that often are 4 to 10 inches long, Upham added, “although judging how big they actually are can be difficult. Worms wiggle, they stretch and they bunch up. They can look really long and thin when they stretch out or short and chunky when they bunch up.”

Nightcrawlers probably are best-known at bait shops and fishing supply stores.

In their unseen natural habitat, they “turn” soil and plant material. Through most of the growing season, they’re earth’s deep diggers, living in permanent burrows 5 to 6 feet straight down, he said.

Now, however, they’re starting to operate close to ground level because of spring’s soil warmup and rains. (If the ground is wet, they’ll do so again next fall.) And, because they eat as they go, the result can be randomly spaced little mounds all over lawns and gardens. Although these bumps may look like rich coffee grounds, they tend to make springtime mowing difficult, Upham said.

“The scattered bumps are nightcrawler middens, which most gardeners would probably think of as worm manure. They’re tiny hills of digested and leftover plant parts that the worms may use as protection or food reserves,” he said. “Worm farmers say these castings are the caviar of fertilizers – you can use as much as you can afford, without burning plants.”

This “caviar” is only one of the benefits of having earthworms at work in a yard. Such benefits can be hard to remember, however, if people are having to fight and struggle to get a mower across a midden-poxed lawn.

“Getting rid of middens is difficult, too. Rolling the lawn while the middens are soft may help temporarily. If you can do it without injuring the turf, raking the castings out to feed the lawn might also be of some help. So long as the nightcrawlers remain active close to ground level, however, they’ll be building or rebuilding mounds,” Upham said. “Besides, even if you wanted to get rid of this kind of beneficial creature, nothing is labeled for nightcrawler control.”

The worms’ digging mixes soil types and improves soil’s tilth or workability. Their burrows open up channels for water and air to penetrate – which is “tremendously helpful in all soils, but particularly those with lots of clay content,” Upham said. “Roots like the channels because of that increased openness and because burrows make it easier for the roots themselves to penetrate out from their planting hole. The castings lining each burrow also supply plant roots with nutrients.”

The horticulturist warned that chemicals used to control pests vary widely in their effects on earthworms. The ones to avoid while nightcrawlers are active include sevin (Sevin), benomyl, copper sulfate and the arsenicals (MSMA, DSMA). Malathion is slightly toxic to earthworms, while Dylox (Proxol) has no effect on them.

-30-

K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward
kward@oznet.ksu.edu
K-State Research& Extension News