Japan's emblematic "sakura" cherry trees have been infected by a contagious mold disease known as witches' broom in at least 18 prefectures, a study by the Flower Association of Japan showed Monday.
The disease makes cherry trees unable to produce flowers and can sometimes kill them in about 10 years, so the association has recommended the removal of the lesions from the affected trees.
According to the study carried out at 53 locations in 28 prefectures from July 2004 to last December, cherry blossom trees at 25 places in 18 prefectures were found infected with witches' broom.
The existence of even one affected tree indicates it is highly likely the disease has already spread to other trees in the area, according to the association.
As the cherry blossom season approaches in Japan, the association hopes more people consider the importance of keeping the "sakura" trees healthy, said Hiroyuki Wada, the group's tree doctor.
The disease does not affect the health of humans.