Beginner

Scientific Name
Limonius spp.

Identification

• Larvae of click beetles
  
• Copper-coloured
  
• Cylindrical
  
• Hard-bodied
  
• 3 pairs of tiny legs near the head-end
  
• Can be seen burrowing into the ungerminated seeds, as well as underground roots and stems of plants
  
• Infested plants do not develop well, and seedlings lack vigour or fail to emerge
  
• Damage is often scattered randomly across the field

Often Confused With
Millipedes
Three-leaf die back

Period of Activity
Wireworms are present all season. Young plants are most susceptible, therefore early-season control is critical. Wireworms have a life cycle of several years. They are likely to be present in fields with a history of the problem or in fields that have recently had sod crops.

Scouting Notes
Wireworms may be monitored in the fall (or in the early spring for later-planted crops) using bait stations. Bury whole carrots 7.5 cm (3 in.) deep, at 10 marked stations across the field. Check the stations in 2- 3 days.

Begin walking fields at the spike to 4-leaf stage, look for stunted plants and/or gaps in the plant stand where the seedlings have failed to emerge. Dig around the seed trench to look for the cause of the damage. Wireworm are often found in the root ball. Record the percentage of the field impacted by root insect damage. Do a plant population count to determine if re-seeding is necessary.

Thresholds
A count of 0.5- 1 wireworm per station indicates a potential problem. Make your planting and seed treatment decisions accordingly.

Fields with a plant population less than 11,000 plants per acre may require replanting.

Advanced

Scientific Name
Limonius spp.

Identification
Wireworms are the larvae of click beetles. They are copper-coloured, cylindrical and hard-bodied. They have 3 pairs of tiny legs near the head-end.

Wireworms can be seen burrowing into the ungerminated seeds, as well as underground roots and stems of plants. Infested plants do not develop well, and seedlings lack vigour or fail to emerge. Damage is often scattered randomly across the field.

Often Confused With
Millipedes
Three-leaf die back

Biology
Wireworm eggs are often laid in small grains, sod or in fields with grassy weed escapes. Many wireworm species have an extended lifecycle. As a result the larvae may be present in a field for 2- 5 years.

Wireworms are most noticeable during the fall and early spring when they come to the soil surface to feed on roots and decaying residue. During the heat of the summer and the winter months, wireworm larvae will migrate deep into the soil for protection.

Period of Activity
Wireworms are present all season. Young plants are most susceptible, therefore early-season control is critical. Wireworms have a life cycle of several years. They are likely to be present in fields with a history of the problem or in fields that have recently had sod crops.

Scouting Notes
Wireworms may be monitored in the fall (or in the early spring for later-planted crops) using bait stations. Bury whole carrots, 7.5 cm (3 in.) deep, at 10 marked stations across the field. Check the stations in 2– 3 days.

Begin walking fields at the spike to 4-leaf stage, look for stunted plants and/or gaps in the plant stand where the seedlings have failed to emerge. Dig around the seed trench to look for the cause of the damage. Wireworm are often found in the root ball. Record the percentage of the field impacted by root insect damage. Do a plant population count to determine if re-seeding is necessary.

Thresholds
A count of 0.5 to 1 wireworm per station indicates a potential problem. Make your planting and seed treatment decisions accordingly.

Fields with a plant population less than 11,000 plants per acre may require replanting.

Management Notes

• Planting into well-prepared, warm soils and avoiding unnecessarily deep planting depths will help encourage early-season growth, reducing the incidence of this pest.
  
• Plant only once the soil has reached an appropriate soil temperature based on the type of sweet corn grown. Supersweet (sh2) varieties will not germinate at soil temperatures lower than 18°C (64°F). Sugar enhanced (se) varieties require temperatures greater than 16°C (61°F). Under cool soil conditions, plant only normal (su) varieties.
  
• Insecticide seed-treatments will usually control these pests. However, where slow germination has reduced the efficacy of the seed treatment, problems may occur, and the field (or portions of it) may need to be replanted.