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Western Bean Cutworm


Western Bean Cutworm

In-Depth Downloads

Pest Facts and Impact on Crop

  • Species name: Striacosta albicosta.
  • Major larval feeding coincides with the ear development.
  • Direct feeding on the ears reduces grain yield.
  • Infestations of several larvae per ear can reduce grain yield up to 15-20%.
  • Feeding may allow mold and other fungal spores to colonize the ear, further reducing grain quality and potentially producing mycotoxins.
  • Larvae are pests of dry beans in the western U.S. and Great Lakes region, and of corn in the Corn Belt.
Map: Approximate Range of Western Bean Cutworm, 2015

Western bean cutworm historically occurred in cornfields of the Great Plains, but has moved into the central and eastern Corn Belt.

Pest Symptoms

  • Leaf and whorl feeding by small stage larvae.
  • Ear penetration and kernel damage by large stage larvae.
  • Secondary infestation by ear molds after protection from shuck covering has been breached.
Feeding by western bean cutworm.
Western bean cutworm damage to ears.

Pest Identification

  • Western bean cutworm: No straight, lateral lines or black tubercles (warts) along the sides.
  • Fall armyworm: Thin white lines down middle of back and 4 large, dark tubercles on “tail” section.
  • Corn earworm: Lateral, thick pale stripe and dark tubercles.
Western Bean Cutworm
Fall Armyworm
Corn Earworm
Damage from western bean cutworm

Damage from western bean cutworm

Western Bean Cutworm Annual Life Cycle in Corn

Western Bean Cutworm Annual Life Cycle in Corn

Integrated Pest Management

  • Populations: Several factors may contribute to increased populations, including mild winters, reduced use of foliar insecticides in corn, and reduced or no tillage.
  • Trapping: Use pheromone traps to determine when to start scouting for eggs; usually during VT-R2 stages.
  • Scouting: Check the upper flag leaf for egg masses after traps indicate moth flight; check 40 plants per field.
  • Economic thresholds:
    • A foliar insecticide should be considered if the percent of infested plants is reached or exceeded, based on crop value ($/bu) and management costs ($/acre).
Western bean cutworm economic thresholds

Source: University of Nebraska. Thresholds based on yield of 220 bu/acre, 30,000 plants/acre, 85 eggs/mass, and 8% larval survival.

  • In-plant protection:
    • Pioneer® brand products with Herculex® I (HX1) and Herculex® XTRA (HXX) insect protection provide moderate levels of in-plant protection for western bean cutworm.
    • A decrease in susceptibility to products with HX1 or HXX insect protection may lead to lower levels of efficacy, which may result in an increased level of ear damage.
    • Please contact your Pioneer representative or consult with your local university extension for more information on best management practices, including a properly timed insecticide application, to improve control of these insects.
  • Insecticides: Time application to coincide with egg hatch.
    • Protection is most effective when egg hatch occurs during pollination.
    • When egg hatch occurs at brown silk stage or later, the larva can move quickly to the ears since fresh pollen is not available on which to feed.
  • Ear molds: If ear molds are a problem, timely harvest and drying may be desirable to prevent mycotoxin formation.



Herculex® 1 Herculex® XTRA   HX1 – Contains the Herculex® I Insect Protection gene which provides protection against European corn borer, southwestern corn borer, black cutworm, fall armyworm, western bean cutworm, lesser corn stalk borer, southern corn stalk borer, and sugarcane borer; and suppresses corn earworm.
HXX – Herculex® XTRA contains both the Herculex I and Herculex RW genes.
Herculex® Insect Protection technology by Dow AgroSciences and Pioneer Hi-Bred. Herculex® and the HX logo are registered trademarks of Dow AgroSciences LLC.

The foregoing is provided for informational use only. Please contact your authorized Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.

PIONEER® brand products are provided subject to the terms and conditions of purchase which are part of the labeling and purchase documents.