Species

Wireome. Family Elateridae

There are many different species of wireworms or "click beetles" that belong to the Elateridae family. In the northwest, specifically the Pacific lowlands, the Ctenicera species are the most commonly found. Others include Agriotes mancus, Limonius agonus

Related species

The false click beetles (Eucnemidae or Cerophytidae) can be very similar in appearance and some species can even "click." However, they are less common and usually occur in wood just beginning to decay.

Host/site

Wireworms are the soil-dwelling larvae of click beetles that attack a range of crops such as carrots, cucurbits, rutabagas, onions, sweet corn, potatoes, sugarbeets, beans, soybeans and peas. They are considered a minor pest with the potential of causing serious damage to crops.

The larvae live and develop in the soil. They injure plants by eating the newly planted stems, feeding on seeds before and after germination; boring into stems, roots and tubers. The plant stand may continue to deteriorate, wither or die because wireworms continue to feed upon the small roots throughout the season.

Identification

Appearance of the pest

• Eggs: The eggs are tiny, white globules found in the soil.
• Larave: are hard, smooth, slender, wire-like worms with a yellowish-cream to a coppery color. They vary from ¼ inches to 1 ¼ - 1 ½ inches when mature. The last body segment is forked or notched.
• Pupa: The entire structure of the adult's body being apparent.
• Adult "click beetle": are bullet-shaped, hard-shelled beetles that are brown to black in color and about 1/3 inch long. Placed on its back, it flips into the air with an audible snap and lands on its feet.

Indicators

Wireworms feed on seeds and root portions of a wide variety of plants. In corn they can destroy germinating seeds and tiny seedlings. Often the wireworm will be found near the damaged or missing seed or plant. Wireworms will also attack young plants, resulting in weakened plants or a reduced stand. Damage is most likely to occur where corn is planted into a field formerly in pasture or weedy alfalfa.

Life cycle -

Wireworms usually take three to four years to develop from the egg to an adult beetle. Most of this time is spent as a larva. Generations overlap, so larvae of all ages may be in the soil at the same time. Wireworm larvae and adults overwinter at least 9 to 24 inches deep in the soil. When soil temperatures reach 50 to 55 degrees Fahrenheit during the spring, larvae and adults move closer to the soil surface. The winter is spent as a larva or beetle in the soil. The larva may live for two to six years in the soil, feeding on roots of weeds, grasses, and other crops. The pupal stage is short, perhaps two weeks, and is spent in a cell in the soil. In the spring the adults become active, fly about, feed, and lay their eggs. Adults may live for as long as 12 months.

Natural Enemies

Nematode Heterorhabditis megadis.

Monitoring

Two sampling procedures are available. One procedure relies on the use of baits placed in the soil which attract the wireworms to the site.

The other involves digging and sifting a soil sample for the presence of wireworms.

Monitoring should be carried out when the soil temperature is 45¼F or above. The soil should not be dry. To sample, dig down about 10 inches and lift the shovel of soil for examination. Round the soil sample off to approximately 6 inches in diameter. Sift through at least 20 shovels of soil from different locations in the garden to check for wireworms. An average of one wireworm per shovel of soil indicates a population of more than 20,000 wireworms per acre. A suggested threshold for corn is an average of 2 or more wireworms per 10 shovels of soil.

Action Thresholds

Prevention of wireworm damage requires treatment before or at planting time. There are no practical or effective ways to control the pest after the crop is planted. An average of one wireworm per shovel of soil indicates a population of more than 20,000 wireworms per acre. A suggested threshold for corn is an average of 2 or more wireworms per 10 shovels of soil.

Cultural and Physical Controls

• Cultivate your soil in May/June when they begin to hatch to expose them to birds
• Destroy infected crops and remove them from the garden.

Biological Controls

The nematode Heterorhabditis megadis attacks wireworms. Heterorhabditis megadis needs to be applied to the soil as the wireworms are hatching and reapplied each year.

Chemical Controls

Since the wireworm is a soil dwelling pest controlling them with a chemical application is difficult and not recommended.

Reference

Bessin, Ric, and Lee Townsend. WIREWORMS. Fact Sheet. Department of Etomology, University of Kentucky, College of Agriculture, Jan. 2010. Web. 12 June 2010. <http://www.ca.uky.edu/entomology/entfacts/ef120.asp>.

Gesell, Stanley, and Dennis Calvin. Wireworms as Pests of Field Crops. Fact Sheet. Penn State College of Agricultural Sciences, 1983. Web. 10 June 2010. <http://ento.psu.edu/extension/factsheets/wireworms>.

Glogoza, Phillip. Wireworm Management for North Dakota Field Crops. Fact Sheet. North Dakota State University Agriculture and University Extension, May 2001. Web. 10 June 2010. <http://www.ag.ndsu.edu/pubs/plantsci/pests/e188-1.htm>.

Ratcliffe, Susan T., Michael E. Gray, and Kevin L. Steffey. Wireworms Family Elateridae (several Species). Fact Sheet. University of Illinos Extension, 2004. Web. 13 June 2010. <http://ipm.illinois.edu/fieldcrops/insects/wireworm/index.html>.