The powdery mildew of roses usually appears in the summer or early autumn. This disease causes the parasitic fungus Sphaerotheca pannosa, which affects all the terrestrial parts of the plant – thorns, buds, young leaves and shoots. In the middle lane, the first signs will appear in the middle of May.
A dirty white ′′powder′′ raid appears on the affected organs. In roses, photosynthesis deteriorates, leaves change shape, dry out and fall off. The buds of flowers do not open, but dry up and fall away. Plant shoots die off, and the plant itself looks depressed. Weakened plants may die in winter. The most responsive to this disease are hybrid tea roses and remontant beauties.
In the summer, the fungus spreads spores (conidia). By the onset of autumn, the fruiting bodies of the fungus develop on the mycelium of the affected plant. Under patches of sleeping buds and cracked bark, the pathogen overwinters. Sharp temperature fluctuations, poor aeration of the soil, lack of light, excess nitrogen fertilizers, lack of calcium in the soil, low or high humidity and thickened plantings can cause the development of a new disease of the rose shrub.
Powdery mildew control measures
- First of all, it is necessary to plant the plants in open, but not ′′draft′′ areas.
- Treatment of plants with anti fungal drugs
- Removal of diseased plant parts
Prevention VS powdery mildew
With the initial defeat of the plant, you can use the popular methods of dealing with the disease. Here will help infusions of horsetail, nettle, sludge, mullein and ash. But it is worth remembering that an overdose can harm the plant. With a stronger damage to the rose with powdery mildew, fungicides should be used, moreover, each time differently, so as not to cause the fungus and its mutation to become addictive. It is necessary to process until the disease disappears with an interval of 10-12 days. With an interval of 7 days, the plant should be sprayed with a solution of 40-50 g of soda ash and 40 g of soap per 10 liters of water or preparations.
In autumn, it is necessary to cut the parts of the plant affected by powdery mildew and burn them. For prophylaxis, before each flowering, root dressings should be carried out with a 0.3% solution of super phosphate and a 0.3% solution of potassium nitrate until the leaves are completely wetted.