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.
Stem Rot caused by a fungus is the most common disease of Desert Roses. The infected portion of the stem may be yellow or black. The decay may be wet or dry. A Desert Rose may heal itself by surrounding the infected area with new growth, called an abscission zone.