Prunus ssiori trees were totally defoliated with an outbreak of Yponomeuta evonymellus during the early summer of 1996 at Dohdaira on Mt. Tanzawa of Kanagawa Prefecture, central Honshu. The trees were covered with webbed tents produced by the larvae. This is the first report on an outbreak of Y. evonymellus in Japan. The life cycle and biology of Y. evonymellus on Mt. Tanzawa are also briefly described.
