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.
How to Control Black Spot on Roses. Controlling black spot on roses is crucial to any rose grower. Black spot is a fungal disease characterized by black spots on the upper side of leaves. Tending to occur in warm, wet weather, usually during wet summers, the leaves of infected roses turn yellow and fall off.