What do green pellets (frass) indicate in relation to sod webworms?

Green pellets, also known as frass, are a key indicator of feeding activity from sod webworms. When these pests consume the foliage of grass, they excrete frass, which can be found on the surface of the turf or mixed within the thatch layer. The presence of this green material signifies that the sod webworms are actively feeding in the area, which can lead to noticeable damage to the turf if the population is significant.

In contrast, the other choices do not accurately describe what frass represents. Grubs are a different type of turf pest, and their presence would not be indicated by the green frass. While frass can be associated with signs of damage to the roots, it specifically points to above-ground feeding activity by sod webworms rather than root-related issues. Although an increased number of frass may correlate with higher insect populations, the frass itself specifically serves as direct evidence of ongoing feeding rather than merely indicating population levels or root damage.