Illustrated identification guide — PestControlBasics.com
🔍 Identification
Adults: small moths (15-20mm wingspan) that fly in a zig-zag pattern over lawns at dusk. Larvae: 15-25mm; green-grey with dark spots; live in silk-lined tubes at the soil surface; feed at night on grass blades. Evidence: irregular brown patches appearing in July-August; birds feeding in area; visible silk tubes at base of grass when parted; larvae found by thinly slicing turf.
🧬 Biology & Behavior
Adults lay eggs on grass blades; larvae hatch and feed on grass blades at the surface through summer. Multiple generations per year in the South. Damage peaks in July-August during hot, dry weather. Cool-season grasses (Kentucky bluegrass, fescue) are most susceptible during summer heat stress.
⚠️ Damage & Health Risk
Irregular brown patches in summer turf; birds (especially starlings, blackbirds) feeding intensively in affected areas; damage typically appears suddenly and expands rapidly during hot, dry periods.
🔧 DIY Treatment
Confirm sod webworm vs. white grubs: sod webworms are on the surface and damage grass blades; white grubs damage roots — turf with grub damage rolls up like a carpet when pulled. Treatment: spinosad or Bt spray (most effective organic); bifenthrin or lambda-cyhalothrin for fast knockdown. Apply in late afternoon — larvae feed at night.
👷 When to Call a Pro
For large lawn areas, professional application with boom sprayer provides more uniform coverage than homeowner hose-end sprayers.