Black Spot of Peach Caused by Alternaria alternata (Fr.) Keissler

A new disease of peach (Prunus persica Batsch var. vulgaris Maxim.), causing brown, sunken lesions and brownish to blackish brown spots with cracks on peach fruits, was found in Okayama prefecture, Japan, in 1995. The disease was observed not only on peach fruits but also on twigs and leaves. An Alternaria sp. was consistently isolated from these diseased fruits, twigs and leaves. The isolates were pathogenic to peach fruits and leaves. Based on the morphological characteristics, the causal fungus was identified as Alternaria alternata (Fr.) Keissler. After cross-inoculation with isolates from peach, Japanese pear and apple, the isolates were found to be pathogenic only to their original host. This is the first report on a peach disease caused by a host-specific A. alternata; therefore, the common name of black spot (`Kokuhanbyo' in Japanese) was proposed.