While watering the plants this past week, our assistant noticed the ornamental popcorn in one of our prominent container plantings had some missing leaf parts. Upon further inspection, the culprit was identified as armyworm.
Those who farm, and perhaps turfgrass managers (golf courses, sod farms, lawn care), are familiar with the grass pest.
Armyworms are caterpillars with chewing mouthparts that can remove fairly large chunks of leaf tissue in one setting. They feed on a wide range of grasses, including corn and wheat, as well as turfgrass and ornamental landscape plants.
They hide during the day and feed at night. They sometimes hide in the tight whorls of the grass plant, making it challenging to find them beyond spotting the damage.
Armyworms can occur in large numbers and often migrate together as they devour plants in their path. For instance, if they are feeding in a wheat field, once the wheat is harvested, they migrate to turfgrass and ornamental areas to continue feeding.
Several northwest Ohio lawns have been destroyed overnight by large numbers of armyworms.
Their feeding on ornamental grasses resembles the damage from grasshoppers. They eat the edge of the leaf blade first, leaving sort of a notch. They hide in the whorl, and if you peel back the layers of the grass blade, you may find frass (bug poop) pellets and, eventually, the caterpillar.
What to do if you find evidence of armyworms
Inspect your plants to see if you find the notching and frass pellets in the whorl. Any damaged grass blades can be removed; be sure to cut as low on the plant as you can. New growth will cover any gaps.
Bacillus thuringiensis is a very safe pesticide that can be used on caterpillars when they are small; however, the ones in our garden are past that stage and require a “bigger gun.” Other conventional insecticides include products containing the active ingredients bifenthrin, carbaryl, permethrin, and others that are labeled for ornamental plants.
For photos and more information about this pest, read this week’s edition of the Buckeye Yard and Garden Line under Bug Bytes at http://bygl.osu.edu.
Pam Corle-Bennett is an Ohio State University Extension horticulture educator and the state Master Gardener volunteer coordinator.
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