STRATEGY A featured segment designed to share business- critical information to seed-selling professionals. Visit to download this department and other tools. The Wily Wireworm: An Unpredictable Pest Farmers are learning to live with these pesky pests as they head further north and west.Joe Funk WIREWORMS ARE A diverse insect group, not a single species. There are more than 9,000 species world- wide, close to 900 species of wireworms can be found in North America. More than 30 different species are known to cause damage to U.S. and Canadian crops. While the larvae are persistent and hardy, the adults, known as click beetles, cause no harm. “I am working in Montana in mostly cereal crops where we have a different set of wireworms than those found in the Midwest,” says Kevin Wanner, Montana State University assistant profes- sor of entomology and an Extension specialist. “The pest’s biology can vary with different species. It is useful to know what species of wire- worms are in your field.” Wireworms have a multi- year lifecycle, living up to seven years in the soil before developing into the adult stage. The adults are only present for maybe three or four weeks in the spring, and it is during this brief stage that adult wireworms earn the name of click beetles. If you are walking through a field in the spring and see a black beetle about one-fourth inch 36 / SEEDWORLD.COM JUNE 2018 long, you can verify whether or not it is a click beetle by turning it over onto its back. Adult wireworm beetles have a unique mechanism by which they pop themselves into the air to get back on their feet. This popping emits an audible clicking sound. Wireworm Biology Wireworm larvae are extremely hardy, and they eat almost anything. “They can feed on decaying organic matter, seeds and germinating seedlings, plants and small animals, and facultative com- binations of all three,” Wanner says. “Crop rotation is gener- ally not an effective control because these insects have such a broad feeding habit.” Wireworms are also tough and resilient, living in the soil for many years. Throughout the year, they move up and down in the soil profile as they seek more comfortable environments. In the winter they move deep into the soil to avoid freezing; in the spring, when the larvae are hungry, they are attracted by higher carbon dioxide content in the upper soil layers and move toward the soil surface in search of food as soil tem- peratures warm. As the soil’s surface layer dries out and gets hotter in the summer, the worms again move deeper into the soil to find moisture and escape the heat. During the late summer when the larvae get large enough and prepare to pupate and become adults, they again return to the top 4 – 6 inches of soil. Here they go through a short pupation and turn into adult click beetles in August and September. After mating, the females deposit from 200 to 400 eggs in the top 6 inches of the soil. The eggs will hatch into larvae within three to seven weeks. The young larvae over- winter in the soil and emerge the following spring to mate, after which the wireworm life cycle begins anew. Depending on the species, the larvae will spend two to seven years living in the soil eating germinating seeds and seedling roots before they develop into adults. The shorter life cycle spe- cies tend to move around from spot to spot in a field and vary in severity from year to year. The longer-lived species tend to stay in the same spot and are less variable year to year. Once there is a significant number of wire- worms in a field, they are likely to persist for many years. Recognizing Damage Wireworms are early season pests that can damage seeds, roots and developing seedlings, causing mortality and stunting which is often visible as a wilting flag leaf. Later in the season, when wheat plants are getting larger, you will see the flag leaf drying because the wireworm is feeding on the stem, according Mitch Stamm, Biology project leader for Seed Solutions at BASF. David Belles, technical asset lead, Seedcare, Syngenta Crop Protection.