Rose disease and insect pest control

powdery mildew

Powdery mildew mostly occurs on young leaves, and other old leaves, flower stems, receptacles and even branches are also commonly infected. When infected, the leaves appear raised, the raised areas become lighter in color and contain white powdery substances, the leaves become uneven and gradually curl up, the bacteria spread, and the entire back of the leaf is covered with a layer of grayish-white mold. In severe cases, the flower buds, pedicels, entire branches, and leaves are covered with a layer of mold, and new buds and leaves are curled up.

The disease often occurs in late autumn to early spring, and is prone to occur when there is a large temperature difference between day and night and the humidity is high. When the night temperature is 15℃ and the humidity is as high as 90%, it is most suitable for the production, germination and infection of pathogen spores. The high temperature of 27℃ and the low humidity of 40%~70% during the day are suitable for the maturation and dispersion of spores. In this case, it is necessary to spray pesticides as soon as possible for prevention. Powdery mildew spores are spread by air movement.

Prevention and treatment methods:

Spray pesticides regularly, using 600 times diluted amylopectin, 800 times diluted thiophanate-methyl and other pesticides for prevention and control. Spraying the medicine once every 7 to 10 days and spraying water on the leaves frequently can effectively reduce the occurrence of powdery mildew. Cut off diseased branches and leaves as soon as possible to reduce the chance of further spread.

Downy Mildew

Downy mildew mainly harms leaves, new shoots, stems, pedicels and petals. The growth point is first infected, and the leaves turn purple to brown-black. Irregular small spots appear on the infected leaves, which then gradually wither or fall off, and the diseased shoots dry up. Flowers, pedicels and petals become infected and develop similar spots.

When the humidity is high, grayish-white mold layers are likely to appear on all diseased parts. No pathogens can be seen when it is dry, but when it is wet, a large amount of mold layer, namely pathogen cysts and sporangia, will grow. The disease mainly occurs in the greenhouse 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 water spit out from the leaf edges or dew condenses on the leaf surface, the disease will last long and be serious.

Prevention and treatment methods:

Disease-resistant varieties should be selected and carefully maintained, with relative humidity controlled below 85%, attention paid to ventilation, and avoid excessive nitrogen fertilizer application. When the disease first occurs, spray 72% Kelu and other pesticides in time.

aphid

Aphids occur year-round and cause damage during dry periods. It needs to be eradicated as soon as possible in the early stages of its occurrence, especially during the period when new buds are developing vigorously. Spraying a variety of pesticides can have a good preventive effect. The key spraying areas are the growing points and the backs of the leaves. Commonly used pesticides include Aphidkiller, etc., and DDT fumigation can also be used, which is more effective, but it cannot be used after flowering.

Red Spider

Red spider mites absorb chlorophyll from leaves, reducing the efficiency of rose photosynthesis. They spread rapidly and can quickly damage the leaves and stop the development of the plant. It often occurs in summer and is most likely to occur when the temperature is high and dry. In the early stage of the occurrence, you can spray 600 times the diluted mite-killer solution, or 1000~1500 times the diluted mite-killer solution for prevention and control, which is effective.