The answer to 'landscape design disease' is that there are several common landscape diseases that can affect the health and appearance of your yard. These include fungal diseases like powdery mildew, root rot, and leaf spot, as well as bacterial infections and pest infestations. Symptoms can include discolored, wilted, or dying foliage, stunted growth, and unsightly patches in your lawn or garden.
In many cases, these issues can be addressed through proper maintenance, like improving drainage, adjusting watering schedules, and using disease-resistant plant varieties. However, severe or recurring problems may require the expertise of a professional landscaper or arborist to properly diagnose and treat the underlying cause.