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.
Proper pruning improves the health of your rose bush, prevents disease and encourages better flowering. There are different pruning strategies for different times of the year, but overall the goal is always the same: keep the bush fresh and open for better air circulation through the center of the plant.