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.
Black Spot. In the spring, my roses were full of leaves and had a lot of blossoms. This year the leaves have black spots, turn yellow and fall off. Some dry up, turn gray and curl up. There is new growth on the bare stems and at the base of the plant, so I know it isn't dead.e have bush type roses that grow on the south side of our home. Over the past few years we have noticed they are becoming infested with some type of pest that creates pods on the stem. It seems to suck the life out of that stem and moves on to another. Inside these pods are small worms.