The Purdue Plant and Pest Diagnostic Laboratory

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September 8, 2014

Armyworm Outbreak Damaging Turf Across Indiana

Doug Richmond, Associate Professor, Department of Entomology, Purdue University

There appears to be a wide-spread outbreak of armyworms [Pseudaletia (=Mythimna) unipuncta (Haworth)] infesting turfgrass across Indiana. These insects typically have 2 generations per year in this part of the country and we are in the midst of the 2nd generation of larvae. Adult armyworm moths lay their eggs in large masses and when the eggs hatch, the resulting caterpillars begin to feed and move across the infested area. When the larvae are small, this feeding causes little damage and may go unnoticed. However, as development proceeds, the larvae increase in size, consuming larger amounts of turf. Where heavy infestations occur, a typical home lawn may seem to disappear almost overnight!! Feeding damage often appears to radiate out from a central point where the eggs were deposited. Although the damage can be alarming, armyworms are easily controlled with insecticides and the damage they cause, although unsightly, will not permanently damage the turf unless it is already stressed from drought. Fortunately, most of Indiana has been experiencing adequate rainfall for the last few weeks, so turf should be resilient to this damage. Still, expect damage to get worse before it gets better. Good cultural practices including adequate fertility and irrigation will help the turf recover more quickly. The caterpillars we are seeing now will pupate by the end of September and attempt to remain in the soil over winter. Unless we experience an exceptionally mild winter, most pupae will not overwinter successfully.

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Figure 1: Armyworm taken from turfgrass in southern Indiana.


Photo courtesy of B. Voges



Figure 2. A home lawn in southern Indiana showing typical armyworm damage.


Photo courtesy of B. Voges

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service