Manage corn rootworm in 2023

MARION, Iowa — While summer is the time to evaluate corn rootworm pressure, now is the time to make plans to manage it, said Andrew Rupe, agronomist at Golden Harvest.

“After harvesting the crop, it is very difficult to understand what the CRW populations are like on a given field if we didn’t scout during the summer,” he explained.

“Many of our evaluation methods are performed during the growing season, including digging roots to score and evaluate the level of CRW feeding and beetle trapping to determine the population in each field.”

At this point in the year, corn roots have decayed and the females have burrowed into the soil to lay their eggs, Rupe said.

“We must try to piece together what we saw while harvesting the crop,” he said. “Was there root lodged or ‘goose-necked’ corn in some of our continuous cornfields? Could that root lodging be the root strength of the hybrid, or was it a result of root feeding?

“We should consider what our CRW management strategy looks like now and evaluate how effective the plan is for the future.”

Five Tips

Rupe shared five corn rootworm management strategies, listed from most effective to least effective against corn rootworm, to consider.

1. Plant a non-host crop, such as soybeans: In most cases, rotation away from corn for a single, complete year will nearly eliminate corn rootworm pressure in that field the following year. If there are no corn roots to feed on, the insect cannot survive.

Also keep in mind that managing volunteer corn in the non-host crop is critical to controlling the corn rootworm population.

2. Combine traits with soil-applied insecticide: The combination of a multi-traited corn hybrid, such as DuracadeViptera, with a soil-applied insecticide is the best combination management practice when continuous corn must be planted in a field.

Farmers with a history of unexpected corn rootworm damage or excessive root feeding may benefit from adding soil applied insecticide to a traited corn hybrid at planting.

3. Plant corn hybrids with below-ground traits: Understand which proteins and how many proteins a corn hybrid has that work against corn rootworm larvae. Corn hybrids may contain zero, one or multiple proteins against CRW larvae.

DuracadeViptera offers multiple unique modes of action to preserve trait durability and delay insect adaptation for long-term field health.

4. Use soil-applied insecticide: Without traits, granular insecticides are typically more effective to control larvae compared to an in-furrow insecticide that is tank mixed with liquid fertilizer.

The one agronomic drawback of an in-furrow insecticide is that it requires moisture to fully activate the chemical in the root zone.

5. Apply a foliar insecticide to reduce corn rootworm adults: In addition to other control methods, if summer scouting indicates a high population of adult CRW beetles, foliar insecticides can be utilized to reduce silk clipping and limit egg laying.

This is sometimes referred to as “beetle bombing a cornfield” and can lower the next generation’s CRW population.

Consider the timing of your insecticide treatment to get the best control possible of the CRW adult females.

If timing aligns, it may be tank mixed with an aerial fungicide application, which will help reduce application costs.

Learn more at GoldenHarvestSeeds.com.