Why Is My Grass Turning Yellow in Spots — Is It a Disease or Something Else?

Yellow spots in a Utah lawn are most commonly caused by dog urine (small bright yellow spots with dark green rings), fertilizer burn (yellow patches right after application), fungal disease (irregular yellow patches), or iron chlorosis (overall yellowing with green veins). Each cause has a distinct pattern — matching the pattern to the cause is the key to fixing it.

Your first instinct is to water more. Don't. Yellow spots have many causes, and watering makes some of them worse.

1. Dog Urine — Most Common

Small bright yellow spots, 4-10 inches across, with a dark green ring around the outside. Female dogs cause more concentrated spots. Flush with water immediately after urination. Apply gypsum to neutralize salts. Reseed dead spots in fall.

2. Fertilizer Burn

Yellow or white streaks following your spreader pattern. Usually appears 1-3 days after fertilizing. Water heavily — apply 1-2 inches over several days to flush excess salts. Stop fertilizing for 4-6 weeks. Use slow-release fertilizer next time.

3. Iron Chlorosis — Utah's Alkaline Soil

Overall yellowing with dark green veins. Utah's soil pH (7.5-8.5) locks up iron so grass can't absorb it. Apply chelated iron spray for fast results (24-48 hours). Lower soil pH with elemental sulfur. Annual iron applications are usually needed.

4. Fungal Disease — Dollar Spot and Rust

Dollar spot: small coin-sized yellow-tan spots that merge. Rust: yellow-orange powder on blades. Both thrive in moist, low-nitrogen conditions. Water deeply but infrequently, increase nitrogen, improve air circulation.

5. Overwatering

Yellow in low-lying areas with spongy soil. Utah clay drains slowly. Stop watering for 5-7 days. Core aerate. See our lawn aeration guide.

6. Mowing Too Short

Yellow on high spots where the mower blade hits. Raise deck to 3-4 inches. Never cut more than 1/3 of the blade at once.

Quick Diagnostic Guide

Yellow spots with green ring = Dog urine.
Stripes matching spreader = Fertilizer burn.
Overall yellow, green veins = Iron chlorosis.
Small coin-sized spots = Dollar spot fungus.
Yellow in wet areas = Overwatering.
Yellow on high spots = Scalping.

For more lawn care help, see our Spring Lawn Care Tips and brown patches guide.

Frequently Asked Questions

Will yellow spots from dog urine grow back?
Yes, in most cases. Flush with water, apply gypsum. Recovers in 2-4 weeks.

How long does fertilizer burn take?
2-4 weeks with heavy watering. Severe cases may need reseeding.

Is yellow grass dead or stressed?
Check the crown at the base. White/light green = alive. Brown/mushy = dead.

For professional lawn care across the Salt Lake Valley, contact TruCo Services.