Sudden Lawn Decline in New Hampshire: Grubs, Fungus & Fertilizer Timing

12-Year Perfect Lawn Suddenly Failing at 1500' Elevation

A Washington, NH homeowner's previously thick, weed-free lawn on a steep wooded hillside now has crabgrass, weeds, yellow circles, matted grass, moss, and slow growth (mowing every 2 weeks vs. 5–6 days). Fertilizer and lime routines unchanged.

Yellow Circles: Two Likely Causes

1. Grubs: Dig between green/yellow areas; look for C-shaped white larvae in root zone
2. Rhizoctonia blight (brown patch): Fungus active in 80–90°F with consistent moisture. Caused by frequent rain or afternoon/evening watering.

Corrective Actions

• Watering: Early morning only, 1–2×/week deeply
• Fertilizer schedule: Light in spring, heavy in early & late fall, NEVER in summer
• Crabgrass: Dig out now; apply crabgrass preventer in early spring (late April) when forsythia buds

Environmental Factors

Steep hillside, wooded setting, and elevation create unique microclimate. Moss suggests shade, acidity, or compaction. Soil test recommended to check pH and nutrients.

The sudden change after 12 years suggests a new stressor (weather pattern, pest introduction, or soil change). Systematic diagnosis and corrected cultural practices should restore the lawn.