Corn rootworm can devastate a corn crop. The larvae can damage corn root tissue and hairs, affecting corn crops early in the season, and the damage can continue when the larvae mature and emerge from the ground, clipping silks. Root damage from larvae can lead to weak plants, causing corn to lodge following wet or windy conditions, making harvest more difficult.
The potential for crop injury is high long before symptoms are observed above ground. Growers can expect 15% yield loss on average for every root node pruned by corn rootworm. Additionally, corn rootworm control is diminished as resistance to older chemistries increases.
Scout Corn Rootworm
Scout for corn rootworm all season long to inform next season’s control decisions. In the Midwest, corn rootworm is active in the field from mid-May to early September. If you see large populations of larvae or adult beetles, it is a sign that your control measures were inadequate this year and that you can likely expect high pressure again next season as the pest overwinters in the soil.
When scouting for corn rootworm, remember these helpful tips from the Iowa State University Extension:
- Gather the proper supplies, including a shovel or spade and black garbage bag or bucket of water. Consider using a hand lens as well. Later in the season, sticky traps are useful scouting tools.
- Expect to see larvae in the first instar stage in late May. This is where a hand lens will come in handy to see the tiny insects.
- Select a random plant. Dig out the plant and surrounding soil. Hand-sort or use the float test, giving the insect ample time to become apparent. Record the average number of larvae on each plant.
- When scouting for adults, use either the sticky trap or in-field plant count method. If using the sticky trap method, place traps along the same row at least 165 feet apart. Leave the traps in the field for a week and record the number of adult corn rootworms. If using the in-field plant method, select two plants within 10 feet of each other in 20 random sites and inspect for adult corn rootworm.
Get Control of Corn Rootworm From the Start
Start the season on the right leaf with a robust soil-applied at-planting insecticide to effectively minimize the risk of corn rootworm damage from season to season, especially if you found corn rootworm last season.
Opello™ insecticide, powered by PLINAZOLIN® technology, provides excellent control of corn rootworm and other soil-dwelling insect pests. By defending roots against below-ground insect feeding, Opello protects overall plant health, reduces the incidence of lodged corn and preserves yield potential.

With an innovative active ingredient in IRAC group 30, Opello offers growers an opportunity to revitalize their management programs and enhance resistance management. Opello gives growers the flexibility to choose to grow continuous corn acres rather than rotating to a non-host crop.

Its compatible formulation blends through tank mixing with a wide range of starter fertilizers without specialized equipment to aid in easier application.
Additionally, Opello provides control of soil pests like wireworm and white grub, helping you protect your seed investment from additional underground pests.
To learn more about how Opello can help you manage soil-dwelling insects in your corn fields, reach out to your Syngenta representative.
Force Evo and Opello are Restricted Use Pesticides.