Wireworms earned their name because they have long, thin, wirelike bodies that range from 1/2 to 1 1/2 inches in length. The larvae of click beetles (Alaus spp.), wireworms have 2- to 10-year life cycles, most of which is spent underground. Although adult click beetles don't damage plants, wireworms feed on the seeds and underground parts of various crops, causing wilting, stunted growth and even plant death. Wireworms are difficult to eliminate, but you have several natural options for reducing pest populations without releasing potentially harmful chemicals into the environment.
Spike the Soil
Because wireworms dwell near the soil's surface from late spring through the summer, you can often eliminate the pests using a spiking tool. Your chosen tool should be very sharp and at least 2 inches in length. Some gardening stores sell specially designed aerator shoes or sandals that spike the soil as you walk across it. You could also use a garden fork, a spike aerator or a plug aerator.
No matter what spiking tool you use, keep in mind that the more holes you make in the soil, the greater the number of wireworms you eradicate. Strive to make the holes an even 2 to 6 inches apart throughout the entire treatment area. Make the spiking process easier by waiting until the day after rainfall or by watering the soil to a 1-inch depth a day or two beforehand.
Set Out Traps
Wireworms feed on a wide range of garden plants, including annuals such as potatoes (Solanum tuberosum) and carrots (Daucus carota var. sativus). Trap the pests with potatoes by cutting the spuds in half, removing the eyes and spearing the pieces on sticks. Bury the potatoes 2 to 4 inches deep at 3- to 10-foot intervals, leaving part of the stick poking out of the ground for easy removal. Wait about seven days and pull up the potato pieces along with the feeding wireworms. Toss the infested potatoes into a covered trash can and plant more pieces. You could also bury fully grown carrots with foliage every 12 inches in infested soil. Wait a week to pull up the trap carrots, remove the wireworms and replace the carrot to bait more pests.
Release Predatory Nematodes
Beneficial nematodes, also called entomopathogenic nematodes, are microscopic, soil-dwelling roundworms that kill wireworm larvae while having no impact on people, animals, plants or fish. The nematodes burrow into the larvae and release a bacteria that quickly multiplies and kills the worms within 48 hours. Look for a product that contains Heterorhabditis megidis, Steinernema riobrave or Steinernema feltiae nematode species for optimal wireworm control.
Beneficial nematodes come in various formulations, including granules and gels. Read and follow the label's mixing and application instructions carefully. One product recommends mixing one package of nematodes and 1 to 2 gallons of water in a bucket. Use a small garden sprayer or watering can to evenly spread the solution over the treatment area. Nematodes need water to make their way through the soil, so moisten the treatment area with 1/4- to 1/2-inch of water about three hours before application. Follow up a nematode treatment with another 1/2-inch of water and keep the soil moist for the following two weeks.
Cultivate the Soil
Regularly cultivating around vegetable or ornamental plants during the growing season can help get rid of wireworms. Dig down as deeply as you can without disturbing the plant roots. This brings the worms to the soil's surface and exposes them to hungry birds. In autumn, remove all garden debris and till the soil to a depth of 6 to 8 inches. Wait about 14 days and till again to a depth of 2 to 4 inches. Do another shallow cultivation of 2 to 4 inches in the early spring about two weeks before you plan to plant. Not only does this expose the pests to birds and the elements, it also disrupts their reproductive cycles so you'll have fewer wireworms the following growing season.