The atmospheric chemistry would be upset by cutting out sunlight. It would be like a nuclear winter and could last for tens of thousands of years. These comets are 200-300km (186 miles) in diameter they are sheer monsters and could sterilise the earth if we are hit by one.
Heat stress â Another reason for rose leaves turning yellow is the rose bush is under some sort of stress. A common cause of stress is heat stress. The rose bush turns yellow and drops its foliage in an effort to cool down in the case of heat stress.
Examine the plant for other disease symptoms known to be associated with black spots on the species. For example, search roses for other black spot disease symptoms caused by the fungal pathogen Diplocarpon rosae, including diminished health, black spots on upper sides of leaves, yellowed foliage, and leaf drop. Look over canes for the presence of purple-hued areas of dying plant tissue.