Armyworms Invade Indiana

There appears to be a wide-spread outbreak of armyworms [Pseudaletia (=Mythimna) unipuncta (Haworth)] infesting residential turf across southern 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.
 

Armyworm taken from turfgrass in southern Indiana. Photo courtesy of B. Voges.

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 main infestation likely started. 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.

A home lawn in southern Indiana showing typical armyworm damage. Photo courtesy of B. Voges.

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.

For control information go to: http://extension.entm.purdue.edu/publications/E-61.pdf

Doug Richmond, Turf Entomologist