What is the primary sign of turf damage from sod webworms?

The primary sign of turf damage from sod webworms is large brown patches in the grass. These patches occur because sod webworms feed on the grass blades, leading to localized areas of dead or damaged turf. As they consume the foliage, the affected areas will often turn brown and eventually die if the infestation is severe enough. Identifying these large brown patches is critical for understanding the extent of the damage and for determining necessary pest management strategies.

The other options, while they may indicate other issues or conditions in the lawn, are not the primary indicators specifically associated with sod webworm damage. Yellow patches may suggest nutrient deficiencies or other pest problems, rolled up grass could be related to environmental stress or other pest activity, and increased insect activity might be observed generally without confirming sod webworm presence. Thus, recognizing the large brown patches is key to diagnosing and addressing the specific damage caused by sod webworms.