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First Report of Powdery Mildew of Pepper in North-Central Mexico

Pepper plants showing general yellowing and white spots on the lower surface as well as brown spots on the upper surface of the lowest leaves were observed during the 1998 crop season in the states of Chihuahua, Zacatecas, and Aguascalientes (north central area of México). Light defoliation was observed. Samples were collected in Chihuahua and Zacatecas to identify the pathogen, which showed navicular conidia. A conidial suspension was sprayed on pepper varieties, but only Hungarian Yellow Wax showed powdery mildew lesions. The average size of the conidia from Zacatecas was 61.2 × 18.2 μm while those from Chihuahua measured 58.2 × 17.6 μm, which is coincident with the description given for an Oidiopsis sp. The perfect stage is Leveillula taurica (1). Cleistothecia were not observed. In Zacatecas the disease was not detected in tomato fields or in sowthistle (Sonchus oleraceae) plants contiguous to, or within, infected pepper fields. Powdery mildew incidence ranged from 35 to 80% in Ancho type and from 0 to 55% in Mirasol type pepper fields in Zacatecas. The number of powdery mildew lesions per leaf in most cases varied from 1 to 3. Incidence was higher in fields where the canopy was closed and warmer and wetter conditions may have allowed the disease to progress.

Reference: (1) J. B. Jones et al. 1991. Compendium of Tomato Diseases. American Phytopathological Society, St. Paul, MN.