Identification & Incidence: Corn planted no-tillage in grassy cover crops, sod or hay is susceptible to armyworms, which are striped larvae that feed on foliage during the pre-whorl and whorl stages. Infestations tend to occur more often during wet spring seasons. Significant armyworm infestation of no-tillage corn following corn or soybeans is rare.

Damaged whorl of corn plant

Identification & Incidence: Corn planted no-tillage in grassy cover crops, sod or hay is susceptible to armyworms, which are striped larvae that feed on foliage during the pre-whorl and whorl stages. Infestations tend to occur more often during wet spring seasons. Significant armyworm infestation of no-tillage corn following corn or soybeans is rare.

Sampling: High risk no-tillage corn planted in grassy ground cover should be inspected regularly. Inspect 20 plants in 5 locations and determine percent of plants damaged and collect a number of armyworm larvae to determine the predominant stage of larval development.

Economic Threshold: If 25% of a stand or more exhibits armyworm injury and potential stand defoliation of 50% or more is anticipated, rescue treatment is warranted. If less than 25% of a stand is infested, inspections should be repeated days later until status of infestation is resolved.

Management Options: High risk corn stands which cannot be scouted may warrant use of preventive treatment. Scouting and rescue treatment is preferred since armyworm is relatively easy to control if detected early. See chart for insecticides labeled for armyworm.