Rose Black Spot Symptoms and Control
Are you familiar with these? Knowledge about roses from the Flower Clinic, symptoms and control of rose black spot, let's learn about it together.
1. Symptoms.
Black spot is most prevalent in Beijing during the summer and autumn seasons. The affected rose plant leaves develop blackish-brown spots 3-4 mm in diameter with a yellow halo around them, the leaves fall off, and in severe cases, only the branches and infected buds remain on the rose plant.
2. Early Prevention
(1) Prevent dripping water on the leaves or spraying during the seedling stage of roses; if spraying is necessary, it should be done on sunny mornings.
(2) Spray with a fungicide (1000 times dilution of carbendazim) before planting to prevent disease. After planting, in May and June when the rose seedlings are not taller than 30 cm, spray the fungicide once a week, and respray promptly after rain. Both sides of the rose leaves should be sprayed each time. Mature old leaves of roses are less likely to be infected; when the roses grow to be over 40 cm tall and have not been infected with black spot during the seedling stage, even without preventive spraying during the rainy season of summer and autumn, rose black spot will not occur.
3. Treat Early and Minimally After Onset
If a small number of diseased leaves appear on roses, remove them promptly. Spray with a fungicide (1000 times dilution of carbendazim) once a week for 4-5 times. After the first removal of diseased leaves, strictly pay attention and remove all new leaves with black spot lesions measuring 1 mm in diameter. Practice has proven that removing the leaves at this stage will not cause re-infection due to the operation. This usually cures the disease in one application. If no new diseased leaves appear after a period of observation, stop the treatment. Generally, if roses grow to 50-60 cm tall without being infected by black spot, there is no need for spraying and black spot will not occur.
The above is a comprehensive explanation of the symptoms and control of rose black spot, hoping it can help you.