Wireworms feed underground on germinating seeds, roots and young seedlings, killing plants directly or wounding them. These wounds are a perfect gateway for opportunistic pathogens that further worsen the symptoms. The occurrence of dead seedlings and hollowed-out seeds soon after planting are telltale signs of an infestation of the soil by this pest. At later stages of plant growth, young plants may wilt and show signs of discoloration. Central leaves may have feeding damage or die while the outer leaves remain green. Stems may be shredded but still attached to the roots. In the field, patches with thin stands or simply bare plants are common. Most of the damage is done during early spring. In potato, wireworms can burrow into potato seed pieces in the spring and into developing tubers in the fall.
The symptoms are caused by the immature larval stage of a group of click beetles (Elateridae). Wireworms can be up to about 2 cm long, have slender, cylindrical bodies and are white, yellowish, or coppery in color. Females lay several hundred eggs singly among the soil particles during the summer. Loose and sandy soils favor their proliferation. The larvae feed on underground plant parts, germinating seeds or young seedlings for 2 to 3 years before reaching maturity. This often results in thin crop stands and lower yields. Beside wheat, they also attack maize, grasses and some vegetables (potato, carrots, onions). Crop damage is usually detected after planting, when it is too late to take effective measures. This makes scouting for wireworms essential prior to planting.
Some ground beetles and rove beetles will feed on wireworms. Larvae of stiletto flies (Therevidae) are also predators of wireworms. Some species of nematodes will also feed on wireworms. The fungus Metarhizium anisopliae seems to infect and kill wireworms. A granular formulation containing this fungus is being tested to determine its potential as a control measure for wireworms.
Always consider an integrated approach with preventive measures and biological treatments if available. Prevention of wireworm damage requires treatment before or at planting time. Seed treatments with insecticides can be used to get some degree of control of their populations. Be aware of the restrictions of use of some of these products in your country.