Identifying Wireworms in Cereal Crops

Identifying Wireworms in Cereal Crops

FS175E
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Ivan Milosavljevic, Washington State University Department of Entomology, Aaron Esser, Washington State University Extension, David Crowder, Washington State University Department of Entomology
Wireworms, the immature stage of the click beetle, are a major best of Pacific Northwest cereal crops. The insect feeds on plants below the surface, causing wilt, stunted growth, or death to young crops. This fact sheet provides descriptions and photographs to assist in the identification of wireworms found in the Northwest.
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Wireworms, the immature stage of the click beetle (Figure 1), continue to be pests of Pacific Northwest cereal crops (Higginbotham et al. 2014). The insects feed on plant structures underground, causing wilt, stunting, and even death to juvenile plants (Figure 2). When the pests infest an area in significantly high numbers, the yields of entire fields can be lost (Andrews et al. 2008).

Surveys taken in Washington, Oregon, and Idaho in 2013 to 2014 found that the species of wireworms present, and their abundance, vary greatly across the regions. Determining which species are present through proper scouting techniques is important for management, because different species vary in their biology, ecology, insecticide susceptibility, and crop impact (Horton 2006). Correct and timely identification prior to spring planting can provide an excellent return on investment.

Distribution of Wireworms in Pacific Northwest Cereal Cropping Systems

In 2013 and 2014, Milosavljevic, Esser, and Crowder conducted a large-scale survey across 20 counties in the inland Pacific Northwest (PNW) to examine the distribution of wireworms in spring and winter wheat fields and in conservation reserve program (CRP) land. Wireworms were present in samples from 87 percent of surveyed fields, and 14 different wireworm species were identified.

Three species were dominant: the Western field wireworm, Limonius infuscatus, the Sugarbeet wireworm, Limonius californicus, and the Great Basin wireworm, Selatosomus pruininus (prior to 2014 this species was known as Ctenicera pruinina). These species represented approximately 90 percent of wireworms collected (Figure 3a). The most frequently found species was the Western field wireworm (41%), followed by Sugarbeet wireworm (28%) and Great Basin wireworm (21%). However, the dominant species detected varied by region, with the Great Basin wireworm confined to the dry-farming regions (less than12 inches precipitation zones), while Western field wireworm and Sugarbeet wireworm were most abundant in intermediate and higher precipitation zones and in irrigated regions (Figure 3b).

Identifying Wireworm Pest Species

Wireworms have slender and cylindrical segmented bodies consisting of a head, thorax with three pairs of legs, and a nine-segmented abdomen (Figure 4a; Berry 1998). The three most dominant species found in the inland PNW can be distinguished from each other based on variations in these body features (Lanchester 1946; Glen et al. 1943). A hand lens or microscope are useful tools for identifying the body structures to determine which species are present in a given field.

Western field wireworms are approximately 0.3 to 0.7 inches long, and yellowish-brown or orange in color (Figure 4b).

Figure 1. Immature stage wireworm (left), pupal stage (center), and adult click beetle (right). Photos by Ivan Milosavljevic.

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