Prevention and Treatment of Rose Powdery Mildew
The editor will share with everyone some experience about roses and rose powdery mildew prevention, which is very useful knowledge. It is recommended to collect it!
Rose powdery mildew is a common disease in roses. In some areas, it can cause severe damage.
Symptoms
Leaves, petioles, flower buds, and young shoots can all be affected. Initially, faded yellow spots appear on the leaves, which gradually expand, and later, a layer of white powdery substance forms, covering the entire leaf in severe cases. Infected young leaves will curl, shrink, and thicken, sometimes turning purple-red. When petioles and young shoots are infected, the affected areas will slightly swell and bend backward. Infected flower buds will have a white powdery mildew layer on the surface, resulting in abnormal flower shapes and inability to bloom properly or at all.
Cause
The causal agent has a sexual generation of the fungus Sphaerotheca pannosa (Wallr.) Lev. The closed ascocarps are spherical to pear-shaped, with a diameter of 85-120 micrometers. The accessory filaments are filiform, few and short, dark brown, and have partitions. Each contains one ascus, which is broadly elliptical to spherical, measuring 88-115x69-75 micrometers. Ascospores are 8, measuring 20-27x12-15 micrometers, broadly elliptical. The asexual generation is Oidium leucoconium, with conidia catenate.
Infection Pathway
The rose powdery mildew fungus overwinters as mycelium in diseased buds, leaves, or branches, and in some areas, it can overwinter as closed ascocarps. The following year, it infects for the first time through ascospores or conidia. It is spread by wind, directly penetrating the epidermis or through stomata. The disease spreads rapidly in warm and humid seasons. Different rose varieties have varying resistance to powdery mildew, with generally light, climbing, and multiflowering varieties being more resistant. However, resistance can be lost due to the emergence of new physiological races. Excessive nitrogen fertilizer in the soil and insufficient potassium fertilizer can lead to more severe disease.
Control Methods
1. In early spring, prune and destroy all dead infected branches to reduce the source of infection. Diseased leaves should be removed early.
2. In greenhouse cultivation, ventilation should be increased to prevent excessive humidity. Avoid excessive nitrogen fertilizer and apply phosphorus and potassium fertilizers appropriately.
3. When using chemicals for control, the spraying should be comprehensive and thorough, protecting the young parts. During the peak growth period of new shoots and rainy seasons, the frequency of spraying should be increased. Initially, you can choose to spray 15% Fenjining wettable powder at a concentration of 1500 times, or 20% Fenruting emulsion at a concentration of 2000 times, or 50% Duoliu suspension at a concentration of 300 times, or 50% Methylextorbin wettable powder at a concentration of 800 times and 75% Baijunqing wettable powder at a concentration of 600 times, spraying every 7-10 days, for 2-3 times.
The above is the complete content on the prevention and treatment of rose powdery mildew. I hope it can help you, and at the same time, I hope everyone comes to see more green plant and flower experience knowledge!