Occurrence of bacterial canker of kiwifruit in Japan: Description of symptoms, isolation of the pathogen and screening of bactericides.

A bacterial canker disease of kiwifruit (Actinidia chinensis) has been observed in Shizuoka Prefecture, Japan. Symptoms appear on trunks, leaders and over-wintering canes from late winter to early spring as cankers and cracks, when red-rusty brown bacterial ooze exudes from these lesions or from apparently healthy buds, leaf scars, lenticels and joints of trunks, leaders and canes. In late spring, brown water-soaked lesions with halos appear on leaves, and wilt or blight of vigorous canes and flower buds is also observed. A characteristic white bacterium is consistently isolated from the affected tissues, isolates of which reproduce typical symptoms on kiwifruit and Actinidia arguta when inoculated either with or without wounding in spring and winter. Kiwifruit leaves are most susceptible to the pathogen just before maturation and are less susceptible at younger and older stages. Climatic conditions such as low temperatures, strong winds, and heavy rainfall appear to promote the disease. Applications of streptomycin, kasugamycin or inorganic copper formulations reduced disease development on leaves.