University of Illinois Extension

Managing Turfgrass Diseases

Turfgrass Disease Development

There are several diseases that could potentially infect turf in northern Illinois. The general environmental conditions occurring on the turf, how the turf is managed, and weather conditions all impact turfgrass disease development. Turf diseases need favorable conditions to develop. The best defense against diseases is to maintain healthy turf through sound cultural practices, avoiding favorable conditions for disease. Disease outbreaks often occur when turfgrasses are not managed properly or are under extreme stress, such as from poor soil conditions or perhaps weather conditions (see Table 1).

Table 1: Disease Requirements & Turf Disease Management

Condition Management Practices to Avoid Disease
Susceptible Grass Plant Resistant species/cultivars
Use of mixtures/blends
Causal Agent
(Fungi for most diseases)
Fungicides (temporary protection)
Can never eliminate all causal agents
Proper Environment for
Causal Agent to Develop
Proper establishment
Proper turf management practices
(watering, fertilizing, etc.)

Fungicides are rarely suggested for use on home lawns. Instead, follow sound lawn care practices to prevent serious problems. When a disease outbreak occurs, follow renovation procedures and adjust future lawn care practices as needed to prevent the disease from returning.

Some Common Turfgrass Disease Scenarios

Low Fertiliy, Moisture, Turf Vigor
Disease Symptoms
Dollar Spot Small blighted areas.
Hourglass lesion girdles blade. Colored band on lesion edge.
Red Thread Pink to red masses on leaf blades.
Threadlike appendages from leaf tips.
Rust Orange pustules on leaf blades.
Orange powder from affected grass.
Yellowish turf.
Turf decline.
Excess Nitrogen Fertility, Thatch
Disease Symptoms
Leafspot/Melting Out Brown to purple lesions (spots) on blades.
Irregular dying areas of grass.
Lesions on grass in margins of dead areas.
Snowmold Irregular matted areas.
"Moldy" appearance in spring.
Heavy Clay Soil, Soil Compaction, Thatch, Poor Establishment
Disease Symptoms
Summer Patch
Necrotic Ring Spot
(Fusarium Blight)
Circular/crescent shaped patches.
Irregular dead areas.
Patches in newer sodded lawns.

Powdery Mildew

Finally, powdery mildew is a common turfgrass disease in shade areas. Powdery mildew is easy to identify; as grass appears whitish in color. Powdery mildew develops primarily on Kentucky bluegrass in the shade. Choose shade tolerant grasses and follow shade lawn management practices.

Written by Bruce Spangenberg, former Extension Educator, Horticulture. University of Illinois Extension.