1. Grey spot disease of poplar is common in Northeast, North China, Northwest and East China, which damages many kinds of poplar.
2. The disease mostly occurs on leaves and young shoots. At the initial stage, it is a water stain, and soon develops into irregular brown spots. The disease spots gradually expand, and finally the center is grayish white (Populus canadensis is multilaterally brown), the edge is grayish brown, and at the later stage, the disease spots produce dark green mold like substances (i.e. conidia).
