Armyworms are a recurring pest issue across Kansas, but several different species fall under the “armyworm” umbrella. Each species varies in its host plants, seasonal activity, and whether it overwinters in the state (Table 1). This article prepared by Jeff Whitworth, K-State Extension Entomology Specialist provides an overview of the major species of concern, with emphasis on the Fall Armyworm and Armyworm, which were the primary issues for Kansas producers in 2025. A brief summary of the Army Cutworm, which is not a true armyworm, is also included. Table 1. Armyworm species that can be found in Kansas.
Major Concerns in 2025: The two species that caused the greatest concern to Kansas producers in 2025 were: Fall armyworm & armyworm (true armyworm). Summaries for each species follow.
Fall Armyworm key characteristics:
· Generations: 2-3 per year in Kansas
· Overwintering: Do not overwinter in Kansas. Moths migrate in during the spring and begin depositing eggs.
· Host Range: Very wide. They feed on grasses and broadleaf plants; nearly any green plant can be affected.
· Seasonal Movement: Typically migrate south again in October
· Monitoring:
o Pheromone traps are available for adult Fall armyworm moths.
o Important note: Trap catches indicate when moths are flying, NOT how many larvae are present or feeding in the fields.
Identification: inverted Y on head capsule and four dark spots on the last abdominal segment. Armyworm key characteristics
· Generations: 2–3 per year in Kansas
· Overwintering: Yes. Overwinter in Kansas. No-till or reduced-till systems may favor overwintering survival.
· Host Range: Primarily grasses. Examples: wheat, brome, turf/lawns including golf courses, sorghum, and corn.
· Biological Control: Historically, parasitoids (especially tachinid flies and small parasitic wasps) helped suppress armyworm populations, but few have been observed in the past 3 years.
Identification: larvae are green to black with stripes of various colors. Head capsule is medium brown with dark markings.
ARMY CUTWORM (not a true Armyworm)
Biology and Seasonal Behavior
· Adult moths (“miller moths”) migrate from the Rocky Mountains in early fall and deposit eggs into the soil.
· Larvae hatch in the fall, feed until cold weather, and overwinter as partly grown larvae.
· Feeding may resume anytime temperatures exceed 50°F, even during winter warm spells.
· Primary damage occurs in early spring when several consecutive days exceed 50–60°F.
Identification: small larvae are light-colored with few distinguishable markings. As they grow, larvae become darker brown or grayish with varying degrees of mottling and several pale, dorsal stripes. The head capsule is darker brown with some mottling.
Damage - army cutworms can severely thin or eliminate stands of wheat, alfalfa, and rangeland grasses. Army cutworms were present in large numbers in 2020 and decimated areas of wheat fields and alfalfa fields in parts of Kansas. However, this was not the case in 2021, and only a few were reported in 2022. Army cutworms develop into “miller” moths, which were a nuisance in spring 2024 and a smaller nuisance in spring 2025.
Stacy Campbell is a Crop Production Extension agent in the Cottonwood District (which includes Barton and Ellis counties) for K-State Research and Extension. You can contact him by e-mail at [email protected] or by calling 785-628-9430.