Blackspot is a plant disease caused by wind borne fungus spores in water drops.They land on the top of the leaves and when growing looks like circular black spots with irregular edges. The infected leaves will finally turn yellow and drop off. If the disease is severe all the leaves will drop off and the plant will have to grow a new set. The quality of the blooms will suffer and the plant will be weakened. Blackspot can not be cured but it can be controlled. In climates where there is a lot of rain in the summer or high humidity it becomes more prevalent. Blackspot can be controlled best by spraying with a dormant oil and sulphur spray in the early spring before the bush leafs out. Then again in the early summer using at half the strength. There are also other ways to keep it control. Clean up all dead and fallen leaves, water when the sun will dry the leaves off or use drip or soaker type hoses, remove first six inches of leaves from the ground up so splashed water won't jump the spores on the leaves, plus feed and water plants well as a weak or stressed plant will succumb more quickly . Finally choose varieties that are disease resistant.
Entered by Lynnette
GardenWeb Home Page | Forums | Forum