Cutworm

Cutworms can be destructive insects on maintained turf areas. Damage can occur any time from late May through the rest of the growing season. Damage is usually most obvious in June through August, when temperatures are highest and cool season grasses are not growing vigorously. Damaged spots can persist for several days. Description: There are several species of cutworms, which attack turf grasses. The adults are dull colored moths with a wingspan of one to two inches. The front wings have distinct scale patterns (faint lines, circles and kidney-shaped spots), which can be used to identify species. The caterpillars (the stage that actually damages turf grass) reach 2 inches in length. Most species have a background color of dull gray or brown but usually have some stripes of brighter or sometimes darker colors. Life Cycle: Each cutworm species has its own life cycle, but most cannot survive the local winters. Adults migrate south in the fall and return on weather fronts in the spring. When the adults return, they begin to lay eggs on the tips of grass blades. Tiny caterpillars only 1/32 inch long hatch and begin to feed on the foliage. Caterpillars go through six or seven molts during their development. As they grow, they gradually move deeper into the thatch, carving burrows, which they line with green excrement. Some large caterpillars stick their heads out of their burrows at night, chop off grass plants, which are within reach, and pull the blades back into the burrow for subsequent feeding. After feeding for two to four weeks, the caterpillars transform in the soil to pupae, which are relatively smooth torpedo-shaped and brown. Damage: Cutworms feed on several kinds of grasses. They seem to be most apparent in turf areas maintained at very low mowing heights. Cutworm damage on turf looks like small pockmarks. Closer examination reveals a small burrow and several grass plants around the perimeter of the burrow, which have been sheared off near ground level. Often these burrows are lined with green, pellet-like matter. This is caterpillar "frass," or excrement. Detection: Cutworm moths and caterpillars are nocturnal, so normal daytime inspections will not unveil the insects. Visual inspection can give an indication of the presence of caterpillars. Take a close look at suspicious looking pockmarks and look for sheared grass plants on the perimeter. Control: Cutworms are relatively susceptible to several turf insecticides. The key to successful control is to apply an insecticide when most of the caterpillars are still very small, if possible. The insecticide should be watered in lightly, just enough to move the insecticide off the blades and into the upper thatch. The area should not be mowed for one or two days after application.