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.
Three tablespoons of 10-10-10 fertilizer are adequate for most plants but plants over 5â² tall respond to 5 tablespoons per month. Two major diseases affect roses: black spot and powdery mildew. Black spot shows up as small black spots on the leaves which cause the leaf to turn yellow and fall off.