Winter Weather Watch: Are Insects Overwintering in Your Fields?

With milder-than-normal temperatures throughout the Corn Belt last fall and this winter, you may be wondering if you'll face increased insect pressure during the 2020 growing season. 

The answer is...maybe. Each insect has its own unique method to aid winter survival, so let’s take a closer look at a few common pests that might be overwintering in your fields.

Corn insects that overwinter 

European Corn Borer (ECB)

For European Corn Borer, the last generation prior to the onset of winter produces overwintering larvae. As these larvae enter the final instar stage of growth, they bore into corn cobs, corn stalks and weed stems to overwinter. These areas provide protection from predators and act as insulation from the severe cold. 

Next the larvae enter a state of diapause—similar to hibernation in vertebrate animals—which allows them to suspend development into the pupal stage. The diapause period varies by temperature and day length and ends when spring conditions are favorable for development to resume. They then progress to the pupal stage and emerge as a moth to produce the season’s first generation of ECB. Bird predation and fungal disease can also impact larval survival.

ECB may have a greater-than-normal survival rate in 2020.

Western Corn Rootworm (WCR)

Western Corn Rootworm have only one generation per year. The adult female beetle deposits its eggs at variable depths in the soil of corn fields. Eggs at deeper depths (3+ inches) have a greater survival rate than those deposited at shallower depths. Soil moisture and crop surface reside act as insulation to help protect the fragile eggs. Tillage can destroy some eggs, as well as expose some to winterkill; however, this does not provide adequate egg loss to use as a control measure.

Based on this information, WCR may have a greater survival rate than normal for 2020. 

Soybean insects that overwinter

Bean Leaf Beetles (BLB)

Bean Leaf Beetles overwinter in the adult beetle stage of growth. They are quite susceptible to cold temperatures and protect themselves from low temperatures by hiding under crop residues, in grassy ditches and by entering cracks in the soil. 

A greater-than-normal percentage of adult BLB may be present this spring. Begin scouting your earliest planted soybean fields as they emerge.


Most grasshoppers overwinter as eggs in the soil—usually in fence rows, waterways or road ditches—or in the soil of the growing crop. Eggs are usually clustered in groups of 25 to 50 and covered with a glue-like substance that attaches the soil around the egg cluster to build a pod-like formation. This offers protection from cold temperatures and moisture changes. Extreme low temperatures and wet conditions at hatching can reduce grasshopper survival rates. 

You should expect a greater survival rate in 2020 for grasshoppers. This insect pest can cause serious economic loss, so scout field borders for nymph grasshopper feeding as crops emerge.

When it comes to weather, things can always change before planting season begins. But it’s safe to predict a greater survival rate for insects heading into the 2020 growing season with the information we currently have.

Let’s build a management strategy together

Ready to get ahead of pest pressure heading into the 2020 growing season? You'll enjoy fair, nationwide pricing when you buy inputs online through FBN Direct. Plus our growing network of FBN Hubs means you can also purchase the products you need in-season and schedule free, convenient pickup at a Hub near you. 

And as an FBN member, you can discuss pest pressure, evaluate products and build a management strategy for your operation with support from our FBN Agronomy team. Just call or text (605) 223-4224 to connect with one of our senior agronomists today.

"Bean Leaf Beetle" by UnitedSoybeanBoard is licensed under CC BY 2.0

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