Your lawn faces threats from below (grubs, mole crickets), above (chinch bugs, armyworms), and within (fungal diseases). This guide covers identification, treatment timing, and prevention for every common lawn problem.
Below-ground pests feed on grass roots, causing patches of turf that wilt, turn brown, and pull up like a carpet. Damage is often mistaken for drought stress or fungal disease.
White grubs — the larvae of Japanese beetles, June bugs, and other scarab beetles — are the most common below-ground lawn pest in the eastern United States. C-shaped white larvae feed on grass roots from late summer through fall and again in spring.
Damage signs: Irregular brown patches that peel back easily. Increased bird, skunk, or raccoon digging (they are eating grubs). More than 10 grubs per square foot in a 4×4-inch deep soil sample indicates treatment is needed.
Treatment: Imidacloprid or chlorantraniliprole applied preventively in June–July before eggs hatch. For existing infestations, carbaryl or trichlorfon provide curative control. Organic options include milky spore and beneficial nematodes.
Mole crickets tunnel through soil and feed on grass roots, primarily in the Southeast. Their tunneling creates spongy, uneven turf that dies in irregular patches.
Treatment: Bifenthrin granular applied in June when nymphs are small. Water in immediately after application. Beneficial nematodes (Steinernema scapterisci) are an effective biological control for mole crickets.
Chinch bugs suck sap from grass blades and inject a toxin that causes yellowing and death. They prefer hot, sunny areas — damage typically starts along driveways, sidewalks, and south-facing slopes. St. Augustine grass is particularly susceptible.
Treatment: Bifenthrin or lambda-cyhalothrin applied to affected areas. Water the lawn the day before treatment to bring chinch bugs to the surface.
Sod webworms are the larvae of lawn moths. They chew grass blades at the soil surface, creating irregularly shaped brown patches. You may notice small tan moths flying in a zigzag pattern over the lawn at dusk — these are the adults laying eggs.
Treatment: Bt (Bacillus thuringiensis var. kurstaki) is an effective organic option that targets caterpillars without harming beneficial insects. Apply in late afternoon when caterpillars are actively feeding. Bifenthrin or spinosad are also effective.
Fall armyworms can devastate an entire lawn in 48 hours. They migrate from the south in late summer and feed voraciously on all grass types. Watch for bird flocks feeding on your lawn — this often precedes visible armyworm damage.
Treatment: Speed is critical. Apply bifenthrin or spinosad immediately upon detection. Mow the lawn short first to improve product contact with the caterpillars.
Lawn diseases are caused by fungi that thrive under specific temperature and moisture conditions. Correct identification matters because different diseases require different treatments.
Circular patches of brown, thinning turf with a distinctive dark "smoke ring" at the outer edge, most visible in early morning dew. Caused by Rhizoctonia solani. Most active when nighttime temperatures exceed 65°F and humidity is high. Common on tall fescue, perennial ryegrass, and St. Augustine grass.
Treatment: Reduce irrigation frequency (water deeply but infrequently). Improve air circulation. Fungicide applications with propiconazole or myclobutanil can control active infections. Avoid high-nitrogen fertilizer during hot, humid weather.
Small, silver-dollar-sized tan spots that can merge into larger damaged areas. White, cobweb-like mycelium visible in early morning dew. Most common on nitrogen-deficient lawns during warm, humid weather.
Treatment: Apply nitrogen fertilizer — dollar spot often resolves when the lawn is properly fed. Reduce thatch buildup. Water deeply in the morning so grass blades dry before evening.
Circles or arcs of dark green grass, dead grass, or mushrooms. Caused by fungi decomposing buried organic matter (old tree roots, construction debris). Not directly harmful to grass in most cases.
Treatment: Core aerate through the ring to improve water penetration. Drench with water to push the hydrophobic fungal mat below root level. Fairy ring is persistent but rarely kills grass permanently.
A healthy lawn is the best defense against pests and diseases. Organic lawn care focuses on building soil health and grass vigor rather than reactive chemical treatment.
For complete organic garden pest management, see our Organic Pest Control Guide and Organic Pest Control Hub.