The answer to 'mulch disease' is that mulch can be susceptible to various fungal diseases that can affect the appearance and health of your landscaping. Common symptoms include discoloration, mold growth, and foul odors. The main causes are typically excess moisture, poor air circulation, and improper mulch application or maintenance.
To address mulch disease, start by ensuring proper mulch depth (2-4 inches), spreading it evenly, and avoiding letting it build up against plant stems or tree trunks. Improve drainage and air flow around the affected areas. You can also try treating the mulch with a fungicide, but for severe or recurring issues, it's best to call in a professional landscaper who can properly diagnose and treat the problem.