Mid-Season Insect Watch: European Corn Borer and Western Bean Cutworm

FBN Network

Jun 01, 2022

By the time you’ve reached the middle of the growing season, your corn crop is hopefully standing tall with ears that are developing kernels… but that also means now is the time to keep a keen eye out for the mid-season insect pressure that could get in the way of your yield potential. 

Let’s take a closer look at two pests — the European Corn Borer and Western Bean Cutworm — to get you familiar with crop signs to look for and treatments to use in response to these pests this season. 

European Corn Borer

The European Corn Borer (ECB) is a species of moth whose life cycle has four stages: 

  • Egg

  • Larva

  • Pupa

  • Adult moth

The larval stage does the damage, and is where control measures are applied to crops. Depending on the region of corn production, there can be 1-4 generations of ECB per year, although two generations per year is most common.

First generation ECB larvae overwinter inside corn stalks and corn cobs, which provide protection for the larva from weather and predators. In early spring, the larvae become active and convert into the pupa stage. Moths then emerge in mid-May through mid-June.

ECB adults (moths) are nocturnal in activity. They mate, and the female moth lays eggs in clusters of 5-30 eggs on the underside of corn leaves near the midrib. Eggs hatch in 4-10 days, and the larva feed in the whorls of the plant, which causes a shot-holed appearance on the leaves as they continue to grow.

As the larvae increase in size, they bore into the tender stalk, forming a cavity within the stalk. The larva then pupate and the second generation moth emerges 7-14 days later. Second generation ECB moths mate, and the female moth lay eggs on the underside of leaves. These lava hatch and feed on remaining pollen in leaf axils and also on corn silks. Eventually, the second generation larvae feed and enter the shanks of ears, ear tips and upper half of corn stalks.

How Will ECB Affect Your Corn Crop?

ECB larvae can inflict harm to your crop in the following ways: 

  • Stalk Damage: ECB-inflicted damage to the stalk can translate to harvest issues due to weakened, broken and lodged stalks. This also provides an entry point for additional insects and possible disease.

  • Shank Feeding: When ECB larvae feed on the ear shank, it may cause ear droppage and make the ear unharvestable. This can result in significant yield loss at the end of the season.

  • Ear Tip Feeding: Ear tip feeding by ECB larvae can lead to kernel loss, which will also impact your yield.

How Do You Scout For and Control ECB? 

Most farmers in North America protect against the pest by planting Bt-corn, but you can still control ECB when growing conventional corn with effective scouting and timely insecticide applications.

ECB does its most damage in its larval stage, and that is where control measures should be applied. Once the larvae have entered the stalk, shank or ear tip, it is very difficult for any insecticide to achieve acceptable control. 

Local extension agencies usually report black light trap information regarding ECB moth flights in your area, which helps in knowing when egg and larva scouting should begin. 

Scouting should be done on a weekly basis, as small larvae are far easier to control. You’ll want to examine 10-20 plants in five random locations across each field to look for the presence of eggs and larval evidence. 

Generally speaking, when 25-30% of plants are infested with ECB, it’s time to take action to control the pests with insecticides. 

Treatment Options and Application Rates

Western Bean Cutworm

Western Bean Cutworm (WBC) is another pest capable of causing significant yield losses in corn production. 

WBC moths emerge from the soil in early July and begin to lay eggs a week before tassel emergence. This can continue for 3-4 weeks, through the milk stage of your corn. Eggs are laid in clusters from 5-50 on the surface leaves in the top half of plants. 

How Will WBC Affect Your Corn Crop?

WBC eggs hatch within 5-10 days, and the small larvae begin to feed on pollen in the tassel. 

After all the pollen has been shed, larvae move to the ears, feeding on the silks and developing kernels. Unlike the cannibalistic corn earworm, multiple WBC larvae can exist on each ear and each larva can feed on and destroy up to 12-20 kernels. 

This damage also allows secondary insects and disease to enter the ear, lowering the grain quality. 

How Do You Scout For and Control WBC? 

Once the WBC larvae enter the ear, they are protected from insecticides. But with diligent weekly scouting and properly timed insecticide applications, WBC control is possible. Treatment is suggested when 4-8% of corn plants exhibit infestation. 

Treatment Options and Application Rates: 

Address Pest Pressure All Season Long With FBN Direct®

You can double down on savings and convenience when you shop for ag chemicals on FBN Direct. Simply buy the crop protection products you need online and get them shipped directly to your farm. 

Warrior® with Zeon® Technology is a registered trademark of Syngenta Crop Protection, LLC. Capture® 2EC-CAL is a registered trademark of FMC Corporation.

Copyright © 2014 - 2023 Farmer's Business Network, Inc. All rights reserved. The sprout logo, "FBN" and "Farmers Business Network" are registered service marks of Farmer's Business Network, Inc. All other trademarks are the property of their respective owners. FBN Direct Services are offered by FBN Inputs, LLC and are available only in states where FBN Inputs, LLC is licensed. FBN Direct is a service mark of Farmer's Business Network, Inc. Herbicides, insecticides, fungicides, adjuvants, and biostimulants can be ordered online and via mobile app. Please contact an FBN Sales representative for fertilizer and seed orders.

ALWAYS READ AND FOLLOW LABEL DIRECTIONS. It is a violation of federal and state/provincial law to use any pesticide product other than in accordance with its label. The distribution, sale and use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. We do not guarantee the accuracy of any information provided on this page or which is provided by us in any form. It is your responsibility to confirm prior to purchase and use that a product is labeled for your specific purposes, including, but not limited to, your target crop or pest and its compatibility with other products in a tank mix.

FBN Network

Jun 01, 2022