A New Disease of Hop Due to a Bacterium

Abstract

i) In Nagano and Yamagata prefectures a disease of hop has occurred in the last few years which is different from the usual Downy Mildew or the Crown Call disease. It was observed from the physiological and pathological points of view.
ii) Considerable degeneration and diminution of the vessels take place in a somewhat lower part of the diseased shoot of the “Witches'-broom” type and “Whip-shaped” materials. The vessels of such materials were often plugged with some mucous substance.
iii) Rod bacterium-like minute bodies were observed in some of the plugged vessels, and in the intercellular spaces of the diseased tissues.
iv) Several strains of bacteria were isolated from “Witches'-broom” type materials.
v) Two positive results were obtained in the preliminary inoculation tests with one of the strains of the isolated bacteria.