Powdery mildew often occurs in young leaves, other old leaves, flower stems, flower bearers and even branches are also generally infected. When infected, the leaves show bulges, the color of the bulges becomes pale and there is white powder, the leaves form uneven and curl gradually, the pathogen spreads, the whole leaf back is covered with a layer of gray white mold, when serious, the buds, pedicels, the whole branches and leaves are covered with a layer of mold, and the new buds and leaves are curled.
The disease usually occurs from late autumn to early spring, and is prone to occur when the temperature difference between day and night is large and the humidity is high. When the temperature is 15 ℃ at night and the humidity is as high as 90%, it is most suitable for the production, germination and infection of spores. When the temperature is 27 ℃ and the humidity is 40% ~ 70%, it is suitable for the mature and emission of spores. In this case, it is necessary to spray medicine as soon as possible. Powdery mildew spreads spores by air flow.
Spray medicine regularly, and control it with 600 times solution of NbZ and 800 times of chlorothalonil. Spray once every 7-10 days, and often spray water on the leaves can effectively reduce the incidence of powdery mildew. Cut off the diseased branches and leaves as soon as possible to reduce the chance of re transmission.
Downy mildew mainly damages leaves, shoots, stems, pedicels and petals. The infected leaves showed irregular spots, then gradually withered or fell off, and the diseased shoots dried up. Flower, pedicel and petal are infected with similar spots.
When the humidity is high, the gray mildew layer is easy to appear in all parts. No pathogen can be seen when dry, but a large number of mould layers grow when wet, i.e. sporangium and sporangium. The greenhouse mainly occurs in spring and autumn. If the temperature difference between day and night is large, the greenhouse is not ventilated, the humidity is close to saturation, and the leaf edge spits water or the leaf surface condenses, the duration is long and the disease is serious.
Disease resistant varieties should be selected and carefully maintained. The relative humidity should be controlled below 85%. Attention should be paid to ventilation, and excessive nitrogen fertilizer should not be applied. 72% Kelu should be sprayed in time in the first time.
Aphids occur all the year round and do harm when they are dry. In the early stage of occurrence, it needs to be eliminated as soon as possible, especially in the period of vigorous development of new buds. The key spraying sites were the growth points and the back of leaves. The commonly used medicament is aphid loujing, etc. it can also be fumigated with dichlorvos, with better effect, but it can not be used after flowering.
Red spider absorbs chlorophyll from the leaves, reduces the photosynthetic efficiency of rose, and spreads rapidly, quickly damages the leaves and stops the plant development. Most of them occur in summer, and most easily in high temperature and dry. In the early stage, it can be treated by spraying 600 times of mite, or using 1000~1500 spray of sharp mite net.
