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Flowering Shrubs – Hydrangea

Hydrangeas are deciduous flowering shrubs that bloom from midsummer to fall. Although the plants are noted for their easy care, there are several insects and diseases to which they are susceptible. Hydrangeas are known to acquire diseases such as leaf spots, blights, wilts and powdery mildews. With early detection, most of these maladies can be eliminated.

Leaf Spots

Caused by the fungus Cercospora hydrangeae, leaf spots first appear as small circular brown or purple spots near the plant’s base. Cercospora leaf spots thrive in warm wet weather. The fungus lays dormant on afflicted fallen leaves through the winter and becomes a source for new disease in the next year. They can be treated by removing the diseased leaves and adding nitrogen to the soil.

Blight

Caused by the fungus Botrytis cinerea, blight appears on the flower buds and blossoms. The petals turn reddish-brown and eventually cover in mold. Blights normally occur during wet, humid seasons and are treated with fungicides.

Wilting

Wilting can be a simple matter of lack of water, or a more serious disease such as mushroom root rot or phytophthora root rot. The plant will wilt and turn yellow if it is infected with one of these diseases. When root rot is the culprit, the best option is to ventilate the soil or try to restart the plant.

Powdery Mildew

Powdery mildew starts with small circular white or light gray powdery patches on the hydrangea leaves. It favors high humidity and low air circulation. If left untreated, the white patches will become large yellow or purple blotches
Read more: http://www.doityourself.com/stry/spotting-pests-and-diseases-on-your-hydrangea#.UMjx2bYtdFQ#ixzz2EsFlrnUi