The answer to 'why is my garden disease' is that there are several common causes of garden disease, including fungal infections, bacterial diseases, and pest infestations. Symptoms can include wilting, discoloration, and rotting of plants. The best solution depends on the specific disease, but may involve using fungicides, removing affected plants, or implementing integrated pest management techniques.
If you're unsure of the cause or how to treat the disease, it's best to consult a professional landscaper or horticulturist. They can diagnose the problem and recommend the most effective treatment. While some minor garden diseases can be managed with DIY methods, more serious or persistent issues often require the expertise of a professional.