Environmental Conditions Prime for Corn Earworm and Western Bean Cutworm Damage

Environmental Conditions Prime for Corn Earworm and Western Bean Cutworm Damage
Entomology – Insect Biology and Management – NC State University
October 5th, 2022 | Syngenta

DOWNERS GROVE, ILL., USA, October 5, 2022 – According to Syngenta agronomists, environmental conditions in many geographies are prime this year for above-ground ear-feeding insects such as corn earworm and western bean cutworm. As corn harvest begins, Syngenta agronomists remind growers to assess this year’s pest pressure and use the information to build a plan that protects yield potential in 2023.

“Damage to corn kernels from ear-feeding insects such as corn earworm and western bean cutworm creates entry points for ear molds, which may produce mycotoxins such as aflatoxin and fumonisins,” says Tim O’Brien, Syngenta corn traits product manager. “Grain containing mycotoxins can be potentially harmful when fed to livestock or result in dockage at grain sale.”

According to Scott Gard, Syngenta agronomist, controlling above-ground pests can be difficult as there are only a few control methods, including applying an insecticide application once 95% of the field has tasseled or using a hybrid that has in-plant VipteraTM trait technology. 

“Truly, the best line of defense against above-ground pests is using a hybrid with Syngenta’s Viptera included,” says Gard. “Viptera is the only trait technology available today that effectively protects against both western bean cutworm and corn earworm – and it’s been performing exceptionally well in protecting fields, especially this year when crop development across fields is so variable.”

Corn Earworm Pressure Can be Difficult to Predict

Most areas of the U.S. can experience corn earworm pressure each season. The pest overwinters in the South and migrates north, making it tough to predict where insect pressures may appear and proper timing of insecticides difficult. Corn earworm larvae usually feed at the ear tip. When disturbed, they will either fight or curl into a C-shape. Up to three generations of corn earworm can occur each year, with later generations feeding on corn ears into August and September.

“It’s important every year to scout fields throughout harvest, and it will continue to be again this year as corn earworm damage and environmental conditions lead to a potential increase in ear molds that produce mycotoxins,” says Gard. “If ear molds are present, timely harvest and proper grain storage are important to limit further mycotoxin development.”

Western Bean Cutworm Difficult to Manage with Insecticides

Another ear-feeding insect is western bean cutworm, which in recent years has progressively spread eastward across the entire Corn Belt, through the Great Lakes region and into Ontario.

“Once western bean cutworm reaches an area, it overwinters in the soil and will continue to reappear again in subsequent years,” says O’Brien. “Some areas saw heavy western bean cutworm moth flight and egg laying in 2022, potentially leading to increased populations for 2023.”

Western bean cutworm eggs are laid on the upper leaves of the corn plant. Larvae feed on tassels, pollen and silks, then chew holes through the husk and devour developing kernels on the ear. Traditional scouting western bean cutworm is laborious and proper timing of insecticide applications is challenging. After larvae enter the ear, they cannot be effectively managed with insecticides.  When assessing damage and resulting ear molds from western bean cutworm feeding, keep a sharp eye out for holes they chewed through husks to reach the ear.

Choosing a Trait Stack is Important to Control Both Above- and Below-Ground Pests

As corn growers plan for 2023, reviewing the success of insect control methods this past season helps guide future plans. Syngenta’s DuracadeVipteraTM provides the industry’s most comprehensive protection against 16 above- and below-ground corn pests, including western bean cutworm, corn earworm, and corn rootworm.


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