Pink Spots On Roses . It can also cause rotting of petals, balling of flowers, and black canker on the bark near cuts or frozen tissue. Often green but occasionally light brown, and sometimes with wings, they may cover (in a colony) the complete growing tip of the plant. Treating Botrytis Blight In Roses from www.gardeningknowhow.com Insects that affect roses are often considered pests. The ones that didn't die, the first bloom flush was spotted the same way. Rose leaves that are badly infected will fall from the bush.