Lawn diseases & weeds: identify and fix
Most lawn problems are easy to fix and easy to misdiagnose — and a wrong guess wastes a season. Fungicide won't fix grub damage, and extra water makes brown patch worse. Here are the problems behind the vast majority of "what's wrong with my lawn?" questions, with the telltale signs of each.
Diseases and pests
🟤 Brown patch
Looks like: roughly circular brown patches from a few inches to several feet wide, often with a darker "smoke ring" edge in morning dew. Shows up in hot, humid weather on lawns watered in the evening or overfed in summer.
Fix: water early morning only, skip summer nitrogen, improve airflow. Fungicide only for severe recurring cases — cultural fixes solve most of it.
⚪ Dollar spot
Looks like: many small straw-colored spots the size of a silver dollar that merge into blotches; blades show tan bands with reddish edges. Common on underfed lawns with overnight moisture.
Fix: this one usually means the lawn is hungry — apply nitrogen, water deeply but less often, and mow with a sharp blade.
🟠 Rust
Looks like: an orange-yellow haze over thin turf; walk through it and orange powder coats your shoes. Late summer, slow-growing, underfed lawns.
Fix: get the grass growing again — light feeding and proper watering. Rust disappears once the lawn outgrows it. Mulch-mow to avoid spreading spores; no fungicide needed.
🪲 Grubs
Looks like: irregular brown patches in late summer/fall where the turf peels back like loose carpet — the C-shaped white larvae underneath have eaten the roots. Skunks and birds digging at the lawn are a giveaway.
Fix: confirm by lifting a square foot of turf: more than 5–6 grubs justifies treatment. Preventive products go down in early summer; curative ones in early fall while grubs are small. Reseed the dead areas.
🐕 Dog spots
Looks like: small dead centers with a lush dark-green ring — the opposite of fungus, which rarely makes surrounding grass greener. Concentrated where a dog urinates.
Fix: flush fresh spots with water, rake out dead centers, patch with seed. A designated potty area beats every product sold for this.
Weeds
🌾 Crabgrass
Looks like: coarse, light-green clumps that sprawl flat like a star, exploding in summer heat along driveways and thin areas. An annual — it dies at frost and returns from seed.
Fix: pre-emergent in early spring (soil ~55°F), before germination. After that: hand-pull small patches and mow high — crabgrass seed needs light at soil level, and a tall dense lawn denies it.
🌼 Dandelion
Looks like: everyone knows the flower — the problem is the taproot, up to 10" deep, that regrows from any fragment left behind.
Fix: pull after rain with a dandelion fork, getting the whole root, or spot-treat with a selective broadleaf herbicide in fall when the plant pulls reserves (and herbicide) down into the root.
🍀 White clover
Looks like: patches of three-leaf foliage with white flower heads, spreading in lawns that haven't been fed. Clover fixes its own nitrogen — it thrives exactly where grass is hungry.
Fix: a regular feeding schedule shifts the advantage back to grass. Or keep it: clover stays green in drought and feeds pollinators.
🌿 Nutsedge
Looks like: glossy, yellow-green blades growing twice as fast as the lawn, with a distinctly triangular stem — roll it between your fingers. Loves soggy, poorly drained spots.
Fix: fix the drainage or watering that keeps the area wet; pulling helps only when done young (it grows from underground tubers). Persistent stands need a sedge-specific herbicide — broadleaf products don't touch it.
Not sure which one you're looking at?
Point your camera at the patch. Lawn Care AI identifies the disease or weed and gives you the treatment plan — before it spreads.
Lawn problems FAQ
Why is my grass turning brown in patches?
Patchy browning has at least five common causes — fungus, grubs, drought, dog spots, or scalping — each with a different fix. Check whether turf lifts like loose carpet (grubs) and whether patches have a smoke-ring edge (brown patch). When in doubt, scan it.
How do I get rid of crabgrass?
Pre-emergent in early spring before soil hits ~55°F, hand-pulling for what slips through, and a tall, dense lawn to stop next year's seeds from germinating.
Does clover mean anything about my lawn?
Yes — it's a signpost for low nitrogen. A regular feeding schedule shrinks it year over year, or keep a little: it feeds pollinators and stays green in drought.