Wireworms represent a common challenge for both commercial agriculture and home gardening, inflicting considerable economic damage by targeting the underground portions of plants. Their feeding habits can lead to significant crop loss across a wide array of cultivated plants. Understanding this organism’s life cycle is the first step in effectively managing its populations. Because they spend the majority of their lives hidden beneath the surface, wireworms are difficult to detect and control.
The True Identity of the Wireworm
Wireworms are not true worms but are the larval stage of beetles belonging to the family Elateridae, commonly known as click beetles. These adult beetles are elongated, hard-shelled, and brown or black, earning their name from a unique mechanism where they flip themselves over with an audible “click.” The adult click beetles pose no threat to crops, as they generally feed on pollen or plant material above ground. They emerge from the soil in the spring to mate, and females lay hundreds of tiny, white eggs in the soil, often preferring grassy or weedy areas.
The extended life cycle of the wireworm makes it a destructive pest, as the larval stage can last from two to six years, depending on the species and environmental conditions. During this extended subterranean phase, they grow in size each season. A single field can contain multiple generations of wireworms at different stages of development simultaneously. Once the larva matures, it pupates in an earthen cell and emerges as a new click beetle, ready to start the cycle over again the following spring.
The Destructive Life Stage
The wireworm larva is characterized by its hard, slender, and segmented body, typically yellowish-brown or tan, giving it a “wire-like” appearance. Fully grown larvae range from one-half to one-and-a-half inches long and possess three pairs of short legs behind the head. Their tough exoskeleton allows them to move slowly through the soil, remaining strictly soil-dwelling and moving in response to moisture and temperature. This feeding activity is concentrated on below-ground plant parts, making damage difficult to diagnose until symptoms appear above ground.
Damage begins when larvae bore directly into germinating seeds, hollowing them out and preventing emergence, often leading to a poor stand. If the seedling emerges, wireworms attack the young plant by severing roots or tunneling into the underground stem, causing the plant to wilt and die. In tuber and root crops like potatoes and carrots, the larvae tunnel into the flesh, creating holes and channels that reduce the quality of the harvest. This damage also creates entry points for secondary infections from plant pathogens.
Environmental Factors and Vulnerable Crops
Wireworm populations tend to flourish in certain environmental conditions, particularly in fields recently converted from pasture or sod, which provides an ideal habitat for egg-laying adult click beetles. High organic matter content, often associated with these previous land uses, supports the larvae as they feed on decaying plant material in their early stages. Poorly drained or consistently moist soils favor wireworm survival, as they rely on soil moisture to move and feed effectively. The larvae move deeper into the soil profile during dry weather or high temperatures to seek out more favorable conditions.
Many crops are susceptible to wireworm damage. Cereal crops such as corn, wheat, and barley are highly susceptible, especially during the early-season stage when seeds are germinating and seedlings are small. Root and tuber crops, including potatoes, carrots, and sweet potatoes, suffer direct damage from larvae tunneling into the edible parts. Other vulnerable vegetables include beans, leafy greens, and various root crops, which are targeted as the larvae feed on roots and underground stems.
Non-Chemical Management Strategies
Managing wireworms without chemical treatments focuses on cultural practices that disrupt their life cycle and physical methods that reduce their numbers. A primary long-term strategy is a planned crop rotation that avoids planting susceptible crops after perennial grass or sod is removed. Planting non-host crops, such as certain legumes or flax, can help starve the larvae over their multi-year life span, gradually reducing the population. Improving soil drainage and aeration creates a less hospitable environment, as wireworms prefer moist, undisturbed soil.
Physical controls offer immediate but localized population reduction, such as utilizing bait traps to monitor and collect the larvae. A common bait involves burying pieces of potato or germinating seeds, like wheat or corn, a few inches deep in the soil and marking their location. The larvae are attracted to the carbon dioxide released by the sprouting seeds or decaying vegetable matter, allowing the traps to be dug up after a few days to remove and destroy the concentrated wireworms. Repeatedly tilling the soil during warm, dry periods also exposes the larvae to the elements and to natural predators like birds.