Q: My husband just came in from cutting the grass and he noticed some small tan-colored moths and some larger brown ones, also a few grasshoppers. How should we best rid our lawn of these pests? I assume they will harm the St. Augustine grass. Please advise us on the best course of action.
A: Several kinds of caterpillars, the immature or larval stage of moths, including sod webworms, armyworms, cutworms and grass loopers may cause damage to all turfgrasses. Bermuda grass is their favorite grass while bahiagrass is the least desirable.
Tropical sod webworms, which feed mostly at night, will chew uneven notches along the sides of grass blades. The grass blade may be almost completely stripped off in patches, and these close-cropped areas soon become yellowish to brownish. The damage may start in August but doesn’t become visible until a large portion of the grass is eaten.
Adults of the fall armyworm are light brown moths with a wingspan of about 1 1/2 inches. The larvae are present from the spring through the fall. The feeding is similar but more scattered throughout the lawn. However, armyworms feed during the day and rest at night. Damage thresholds vary in different areas but as a rough estimate you need to apply a pesticide if you have 15 or more larvae per square yard. Your local nursery or garden center will have plenty of pesticide options you can use to deal with these pests. Be sure to follow the directions on the label because “the label is the law”.
The grasshoppers are difficult to eradicate once they are adults although I would not ignore them. I take great pleasure in crushing them between two bricks if I catch any of them on my citrus.