Prevention and treatment of powdery mildew of rose

Rose powdery mildew is mainly harmful to rose, prunes, roses and so on. The disease affects plant leaves, twigs and buds, with an incidence of 50%, 70%, and can prevent buds from blooming or make flowers smaller. The pathogen is Rosa monocystis. The pathogen overwinters with hyphae on the branches, buds and fallen leaves of the host. If the temperature is suitable in the next spring (18 ℃-25 ℃), a large number of conidia can be transmitted and infected. From September to October after summer, the spores were infected again by the wind. Under the condition of 20 ℃ temperature and 97% humidity, the spores sprouted in 4 hours and formed pollinospores in 3 days. Generally, the night temperature is lower (15 ℃-16 ℃) and the humidity is higher (90% Muth99%), which is beneficial to spore germination and infection. High daytime temperature (23 ℃-27 ℃) and low humidity (40% Mur70%) are beneficial to the formation and release of spores.

In early spring, the pathogen was covered with powdery mildew layer on both sides of the unfolded leaves. The leaves wrinkled and curled, thickened to purplish green, and gradually withered and died. During the growing season, the leaves were infected, first appeared small white powder spots, and gradually expanded into round or irregular powder spots. In severe cases, the white powder spots connected with each other, the internodes shortened, the leaves shrunk and withered, and the branches developed malformed. The powdery layer on leaves, petioles and prickles is too thick to peel off. The flower buds are covered with powdery layer, withered and withered, the flowers are small and few, and even do not blossom or bloom malformed.

First of all, to create a good environment for prevention and control, strengthen cultivation management, adequate light, good ventilation, watering during the day. Avoid excessive application of nitrogen fertilizer, properly increase the application of potassium fertilizer, the soil keeps good drainage and improves the ability of disease resistance. During the dormant period, 2Mel 3-degree stone sulfur mixture should be sprayed to eliminate the overwintering hyphae in the disease buds or the closed capsule of the disease. During the disease period, diseased branches, leaves and buds should be thoroughly cut off, and the surrounding rotten diseased leaves should be removed to reduce the source of infection. Combined with diseased branch pruning, alternately spray 70% methyl thiophanate wettable powder 700 Mel 800 times, or 50% carbendazim solution.

The white powdery matter on the surface of the diseased plant is very easy to spread with the help of the wind, the prevention and control is not timely or the diseased branches clean up the unclean and windy environment, which is conducive to the spread of bacteria and re-infection, which is difficult to control. Therefore, should be more observation, early detection, timely spray prevention and control, can achieve good results.