Tuesday, May 21, 2024

Managing insects in corn

corn wireworm
Corn wireworm — photo courtesy University of Florida

Corn producers know that corn is most vulnerable to insects pressures within the first four weeks. For that reason, pre-plant herbicide burndown applications and other integrated pest management practices are key to a successful crop.

Seed treatments are important

Alabama Cooperative Extension System entomologist Katelyn Kesheimer said seed treatments are a great option for producers to give corn seeds an edge at planting.

“Seed treatments act as insurance during the first month when seeds are really vulnerable to below-ground pests that can feed on the seed and lead to diseases,” Kesheimer said. “A high infestation level, high-risk situations in the field or unfavorable growing conditions would be exceptions.”

She said most growers will get adequate coverage and protection with seed treatments at label rates.

High-risk growing conditions

“Field history will tell producers where a risk level is early in the season,” Kesheimer said. “Most problem fields in corn production are rotating out of pasture or conservation reserve program land.”

These fields have high pressures from underground insect pests. While reduced and no-till fields are great for soil conservation and nutrient management, the practices can be problematic for pest pressures. Reduced and no-till situations tend to give insect populations a better chance of survival compared to the survival rate of being disrupted by mechanical turning of the soil.

fall armyworm
Fall armyworm caterpillar and adult moth

Kesheimer said traditional plowing brings underground insects to the surface to be preyed upon by birds and other predators. Keeping ground cover intact creates a prime environment for insect species to thrive and overwinter.

“Understanding the local landscape is key to determining the risk factors in relation to a given field,” she said.

When operating in reduced and no-till situations, burndown is important to reduce potential habitats for insect pests. Kesheimer said the ideal time to apply a burndown herbicide is within thirty days prior to planting.

Common pests

Wireworms and white grubs are underground pests that can feed on both seeds and seedlings. Common surface pests are cutworms and armyworms. Producers may also have occasional issues with sugarcane beetles.

“Sugarcane beetles are cyclical, but entomologists are unsure of exactly what the cycle is,” Kesheimer said.

Corn replant considerations

It is important to look at the entire system when analyzing whether or not to replant.

“Get out in the field, get an estimated stand count and determine what your projected yield is going to be,” she said. “If a producer is within the 30-day window and has already lost half of the stand, it may be economical to consider replanting. If you’re past the 30-day window, it is likely that you will not be able to recoup the costs or realistically get a better stand.”

Consider costs of labor, trips down the field and seed when trying to determine the economic impact of a replant. In situations where a replant is necessary, producers will need to terminate the current stand. It is nearly impossible to manage a corn field with two different growth stages.

Variety selection

When it comes to picking variety, yield and disease package are key.

“You know your farm and your situation better than anyone,” Kesheimer said. “Pay close attention to the Bt genes that you need. It is also important to pay attention to the refuge requirements for each variety.”

Researchers are beginning on-farm trials for non-Bt gene corn, so Alabama producers can look for real-time reports as observations are made throughout the growing season.

Alabama Cooperative Extension contributed this article.

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