Diseases of pepper (
Powdery mildew
Powdery mildew of pepper is caused by the fungus Leveillula taurica. Like other powdery mildews, Leveillula taurica is an obligate parasite and will grow only on living tissue. Its hosts include tomato, eggplant and probably some weeds. The initial symptom on pepper is the appearance of small white to light grey colored spots on the underside of the leaf (photo 1). In early infections, these spots often appear first on the lower leaves inside the canopy of the plant. The fungus produces asexual spores on conidiophores that emerge through stomatal openings (photo 2). The mycelium is inside the leaf, so it does not have a white powdery appearance like other powdery mildews. Later infections may cause yellowing or appear as raised pimply areas (photo 3). Infected leaves may curl resulting in the exposure of the fruit to sunburn (photo 4). Fruits are not infected.
Disease is difficult to control once leaves become infected, therefore preventive measures are necessary in the early stages of disease. Wettable sulfur, dusting sulfur and Flint (Bayer Ag Chemicals) are registered for use on peppers and give good control if applied preventively in both field and greenhouse peppers. Serenade, a biological, has some efficacy at low levels of disease in the greenhouse. There are no resistant varieties of pepper, but hot chiles seem to have less disease than bells, long greens or sweet jalapenos, and chiles grown under center pivot in southeastern Arizona reportedly have had little disease.
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February 24, 2003