Wireworms

Adult click beetles are elongated, dark, and streamlined, and are named for the clicking mechanism they use to flip upright if turned on their back. The larvae, wireworms, are hard, shiny, jointed, cylindrical, and yellow-brown, growing up to about two and a half centimetres.

Adult beetles lay eggs in soil, especially in grassy or weedy areas, during spring and summer. Larvae then live in the soil for multiple years, feeding intermittently and moving through the soil profile seasonally, staying deeper during cold or dry periods and closer to the surface in moist, mild conditions, before eventually pupating and emerging as adults.

Larvae feed on planted seeds and germinating seedlings, creating gaps in the crop stand, and tunnel into roots and below-ground storage organs such as potato tubers, causing internal tunnels and surface scarring that reduce marketability.

Host crops include potato, maize, and sugar beet among others, with risk often elevated in fields with a recent history of grassland or pasture.

Pre-plant bait traps, such as buried grain or potato pieces checked after one to two weeks, help estimate wireworm risk before a susceptible crop is planted. Soil sampling and a review of field history, particularly recent grassland or sod, provide additional risk indicators.

Because wireworms persist in soil for years, management focuses on pre-plant risk assessment and reducing conditions that favour large populations.

• Use pre-plant bait trapping or soil sampling to assess risk before planting susceptible crops
• Avoid planting highly susceptible crops immediately after grassland or sod where risk is high
• Conserve ground beetles, entomopathogenic nematodes, and other natural enemies
• Manage soil drainage, since larvae move toward moist soil zones
• Rotate away from high-risk sequences where wireworm pressure is known to be elevated