Preliminary report on the leaf spot disease of Camellias caused by Graphiothecium Kusanoi sp. nov.

Abstract

1. In 1936 a new leaf disease of Camellia japonica var. spontanea was found in the Tokyo Imperial University Forest, Kiyosumi, Awa; and its symptom, etiology, pathology and distribution were studied.2. On the upper surface of the leaf, there first appear minute discolored specks, which gradually enlarge to circular spots, 2-4 mm in diameter. The spots, having indistinct margins, are at first pale green and become later greenish white. Turning black in the centers, the spots assume “snakeeye” form.3. The disease is caused by a parasitic fungus. It invades through the stoma on the under surface of the leaf into the mesophyll, and forms its stroma in the respiratory cavity. The invaded tissues perish and turn brown, while the cells surrounding them undergo division. The stroma, breaking the overlying epidermis, is exposed as a conical protuberance, measuring 1 mm in diameter and 0.5 mm high. On the stroma, many synnemata are developed, measuring 70×850μ, producing conidia in Penicillium type. The conidia are hyaline, ovoid or ellipsoid, and catenate, measuring 6.0-10.6×3.5-4.5μ.4. The “leaf spot” is proposed as the name of the disease and the causal fungus is described under the name of Graphiothecium Kusanoi sp. nov.