Sod webworm larva have damaged this lawn by chewing leaf blades near the soil surface.
There are several diseases which could potentially infect home lawns in northern Illinois. The general environmental conditions occurring on the lawn, how the lawn is managed, and weather conditions all impact lawn disease development. Lawn diseases need favorable conditions to develop. The best defense against home lawn diseases is to maintain a healthy lawn through sound cultural practices, avoiding favorable conditions for disease. Disease outbreaks often occur when lawns are not managed properly or are under extreme stress, such as from poor soil conditions or perhaps weather conditions. The following table outlines disease requirements and how to manage lawns to reduce diseases.
| Condition | Management Practices to Avoid Disease |
| Susceptible Grass Plant | Resistant Species/Varieties 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 Lawn Practices (e.g., watering and fertilizing) |
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 outlined in Thatch and Lawn Renovations and adjust future lawn care practices as needed to prevent the disease from returning. Lawn diseases common in northern Illinois and the scenarios that cause them are outlined in the following table.
Low Fertility, 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 Lawn Lawn 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 |
Heavy infestations of dollar spot may be due to low soil fertility or susceptible cultivars.
Summer patch has infected stressed grasses on this slope.
Brown patch may infect well-watered and fertilized lawns in hot, humid weather.
