When the black spot of the rose is serious, all the lower and middle leaves of the whole plant can be shed, leaving only a small amount of new leaves at the top, which directly affects the growth, flowering and ornamental effects of the rose.
After the leaves of the rose are dyed, there are different purple-brown round spots or irregular-shaped lesions, which are not very obvious at the beginning; the later spots are purple-brown or brown, and the radiation is clearly visible. In severe cases, the lower leaves are light and the branches are dry. The bacteria overwinter in dead leaves or soil. Poor ventilation, lack of light, low water accumulation, poor sanitation, improper application of fertilizer and water, etc. are conducive to the onset. The black spot of the rose should be mainly prevention, and timely prevention and treatment in the early stage of the disease will be twice as effective. Once it is late, it is difficult to control its spread with pesticide control.
When planting the rose, try to use excellent disease-resistant varieties and strengthen the cultivation and management of seedlings. When watering, try not to spray, and water the roots of the seedlings. If conditions permit, it is best to use drip irrigation, furrow irrigation or watering along the basin. It is not watered at night, so as not to dry quickly when there is water on the leaves, and the bacteria invade. Temporarily trimmed to make the plants ventilate and illuminate, and at least 6 hours of light per day is guaranteed. During the onset of the disease, less nitrogen fertilizer was applied and more phosphorus and potassium fertilizer were applied.
Clean the leaves at any time, remove the diseased leaves, and reduce the source of the infection. Heavy-duty strains are heavily pruned in winter to remove the overwintering pathogens on the diseased stems. Do not touch the leaves of the diseased plants with your hands to prevent artificial transmission.
In the spring of the next year, before the germination of the rose, spray the crystal stone sulphur mixture 100 times. In the summer, when the new leaves are unfolded, they start spraying until the winter. At the beginning of the disease, alternately spray 75% chlorothalonil wettable powder 1000 times solution, or 45% thiabendazole (Tecto) suspension agent 500 to 600 times solution, 40% flusilazole or 25% nitrile emulsifiable concentrate 800 times. Spray once a day in the rainy season, spray once every 7 days to 10 days in the normal growing season and the rainy season, and spray 4 to 5 times to control the spread of the disease. When the incidence is serious, it can be sprayed 70% to kill, 30% copper oxychloride suspension agent 800 times, 75% chlorothalonil 500 times, 12.5% ​​clear milk 1000 times liquid, 7 days to 10 days spray once, even Spray 3 times to 5 times. Among them, 12.5% ​​clear (spotted off) emulsifiable concentrate 1000 times liquid, 75% chlorothalonil 500 times liquid has the best control effect.
For more information, please visit the China Pesticide Network .
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