Armyworms can cause devastating damage

Andrea Burns
Ford County Extension Agent

Armyworms are marching their way across Ford County.  Ag producers and homeowners alike need to be scouting for them and preparing their plan of attack.   

Armyworms are the caterpillars of several species of night-flying moths. Armyworms can be up to 1 3/4 inches long. True armyworms are plump, sparsely-haired, generally green to brown larvae, with dark stripes running down the sides and back. These caterpillars feed on the aboveground plant parts of many grasses and is a pest of many garden and field crops. 

We are beginning to see the second or third generation of cutworms emerging in late summer and early fall.  Cutworm larvae stop feeding and seek concealed areas to spend the winter during mid-fall. In contrast, many of the armyworms are not successful in over-wintering in Kansas. 

The damage cutworms do, can be devastating. Cutworms feed on grass blades and cut plants off near the soil surface. The affected grasses appear ragged and may turn brown from the feeding of any of these larvae.  Damage is more likely to occur if the lawn borders cropland or large untended fields. 

Armyworms, in particular, seem to be attracted to areas of lush vegetation. Inspect lawns more frequently when vegetation in these nearby ‘source zones’ is destroyed, forcing the caterpillars to seek out new food 

If the damage is severe enough and the number of cutworms high enough, some recommended insecticides include:   acephate (Acephate, Bonide Systemic Insect Control); Bacillus thuringiensis var. kurstaki (Dipel, Thuricide); bifenthrin (Talstar, Bonide Eight Flower & Vegetable Granules, Hi-Yield Bug Blaster Bifenthrin, Ortho Home Defense Insect Killer for Lawn & Landscape); carbaryl (various carbaryl and some Sevin products); cyfluthrin (Tempo, BioAdvanced Vegetable & Garden Insect Spray); fluvalinate (Mavrik); fonofos (Crusade); lambda-cyhalothrin (Scimitar, Bonide Garden & Home RTU, Spectracide Triazicide); and trichlorfon (Dylox, BioAdvanced 24 Hour Grub Control, Proxol). 

Always read and follow the label directions.  For more information, on armyworms, contact the Ford County Extension Office or visit our webpage at www.ford.ksu.edu.  Enjoy the fall weather!