Diagnosing Brown Spots: Grubs vs. Disease

Check for Grubs First

Tug on brown grass. If it lifts like carpet, grubs are eating roots. Dig at the green/brown border—white C-shaped larvae confirm it. Apply grubicide (e.g., Grub-Ex) now and repeat in June.

If Not Grubs, Consider Disease

Fungal diseases show hourglass lesions, colored spots/powder, or black roots on blades at patch edges. Apply a standalone fungicide (no fertilizer combo). But real control comes from cultural change: mow high (2.5–3.5"), water deeply once weekly, avoid evening wetness.

Fertilizer Schedule for Western WA

Late spring, early fall, late fall. No early spring or summer nitrogen. Cool-season grasses need this rhythm.