Podosphaera xanthii and Oidium lycopersicum grow on both surfaces of a leaf and form haustoria within some epidermal cells to absorb nutrients. They produce spores on both surfaces. In contrast, Leveillula taurica grows only within a leaf until it produces spores, a growth habit which is similar to Alternaria and most other foliar plant pathogenic fungi. Leveillula taurica is a species complex that infects over 1000 plant species in 74 families, including tomato and eggplant as well as pepper. Detecting powdery mildew on pepper can be difficult.
Affected leaves tend to drop off the plant, as occurs with bacterial leaf spot.
Powdery mildew of pepper was first reported in North America in 1971 when it was seen in southwest Florida. It has not been seen in Georgia, Connecticut, Massachusetts, New Jersey, North Carolina, or Ohio. This disease has been a recurring problem on both chili peppers and bell peppers in all production districts in California since the early 1990s. The same pathogen also attacks tomato in California. Both sightings of powdery mildew on pepper in NY were in commercial production fields planted with transplants from both Georgia and Florida.