Red Tip Photinia (Photinia × fraseri)

Diplocarpon is a group of leaf-spot fungi best known for causing black spot on roses. It spreads by splashing water and thrives on wet leaves in cool to mild, damp weather. Look for round, dark spots with fringed or feathery edges on leaves, followed by yellowing and early leaf drop; stems can develop purple‑black lesions. Roses are most often affected, but similar leaf spots can occur on strawberry and on apple/crabapple. Repeated infections weaken plants and reduce flowering and vigor.

Fire blight is a highly destructive and contagious bacterial disease caused by Erwinia amylovora. It primarily affects plants in the Rosaceae family, including apple, pear, quince trees, and various ornamental plants. The disease can destroy an entire orchard in a single growing season under ideal conditions, with the bacterium moving approximately 11 inches per week in new growth.

Powdery mildew is a common fungal disease caused by various fungi species including Erysiphe, Podosphaera, Oïdium, and Leveillula. It affects over 10,000 plant species worldwide. The disease thrives in warm, dry climates with high humidity and appears as a distinctive white powdery coating on plant surfaces.

Root rot is a serious fungal disease that affects the root system of plants, causing them to decay and die. It is primarily caused by overwatering, poor drainage, or soil-borne fungi such as Pythium, Phytophthora, Rhizoctonia, and Fusarium. The disease thrives in waterlogged conditions where roots are deprived of oxygen, making them susceptible to fungal infection.