How to prevent and cure scab in rose?

How to prevent and cure scab in rose? Please help guide scab to be the most prevalent in summer and autumn in Beijing. Black-brown spots with a diameter of 3-4 mm appeared on the leaves of diseased rose plants, and there were yellow halos around them, and the leaves fell off. When the disease was serious, only branches and infected buds were left. 2. Early prevention (1) to prevent dripping and sprinkler irrigation on leaves at the seedling stage, sprinkler irrigation must be carried out in the morning on a sunny day. (2) spray 8-1000 times chlorothalonil to prevent disease before planting operation. From May to June after planting, when the height of rose seedlings is not more than 30 cm, spray once a week and spray in time after rain. Spray both sides of rose leaves every time. The mature old leaves of rose are not easy to infect, the height of the month is more than 40 cm, the seedling stage is not infected with scab, to the rainy season in summer and autumn, if there is no medication to prevent it, scab will not occur. 3. After the onset of the disease, there are a small number of diseased leaves in the rose, which should be removed in time. Spray 8-1000 times chlorothalonil in time, once a week for 4-5 times. After the diseased leaves were removed for the first time, strict attention should be paid to the rediscovery of black star disease spots in the new leaves, all of which were removed when the diameter of the disease spot was 1 mm. Practice has proved that the removal of diseased leaves at this time will not be reinfected as a result of operation. In this way, you can generally get a radical cure at once, observe that there is no occurrence of new diseased leaves, and stop treatment. Generally rose grows more than 50-60 cm without scab infection, without spray control, scab will not occur. Click to get more rose planting techniques click to get more flower planting techniques