Problems they can cause: Cutworm & Armyworm feed on the foliage of turfgrass at the soil surface.
What are Cutworms & Armyworms?
There are approximately six species of Cutworm and Armyworm that are pests of turfgrass in the United States and it is the larval stage of the insects that are responsible for damage. The difference between Cutworms and Armyworms is their population and behavior. When a population of cutworms is high, they will move across a lawn in a front much like an army on the march, defoliating the lawn very quickly. When this happens, these cutworms are termed armyworms.
Signs of Cutworms & Armyworms in your lawn
Cutworms and Armyworms overwinter as adults in the deep south, migrating northward when warm weather returns. These insects are important pests of agricultural crops but will feed on turfgrasses as well, especially if severe weather carries them beyond areas of intensive agriculture into the more urban northeastern states. Not finding the usual sites to lay eggs such as corn fields, migrating adults will choose the next best area of plentiful greenery – lawns. Most often, cutworms are found in small numbers and do not cause noticeable or significant damage to lawns. However, on rare occasions, there are outbreaks that have numbers that overwhelm lawns, leaving them defoliated.
How to prevent & control Cutworm & Armyworm
Little if anything can be done to prevent an outbreak of these insects; populations spring up randomly with no rhyme or reason. Damage caused by Cutworms & Armyworms is more significant as mowing heights are lowered, so adhering to the optimum mowing height for home lawns helps mask damage without the use of insecticides.
How to repair lawn damage from Cutworms & Armyworms?
Damage caused appears catastrophic but is reversible and will grow back in a couple of weeks. Proper fertilization and irrigation techniques give turfgrasses the resources necessary to replace foliage that was grazed upon.
In the rare instance where an insecticide application is warranted, a synthetic pyrethroid is the best choice.