Lawn diseases are caused by plant pathogens, usually fungi. The fungi are almost always around, living off dead and decaying material in the soil. You just don't notice them because the grass usually fends them off. (They are not dangerous to people.)
But when the environmental conditions are right (usually plenty of moisture and the fungi's favorite temperature) and your grass is stressed, the scale tips in favor of the pathogen. The result? Check out pictures of these common lawn diseases.
Preventing disease problems is the best strategy, because once symptoms are visible, chemical rescue treatments aren't recommended for home lawns. Prevention means maintaining a healthy turf through proper mowing, watering, and fertilizing. In particular:
- Keep leaves dry. If you water, do it early in the morning so that leaves dry quickly. Avoid watering at night.
- Avoid overfertilizing. Too much fertilizer can stress plants and leave them vulnerable to diseases.
- Plant disease-resistant grasses. Choose the right grass for the site.
- Improve drainage. Poorly drained low spots are particularly prone to disease.
- Increase air flow. Lawn diseases are more likely where stagnant air collects. Clear underbrush to improve air circulation.