Mildew

Powdery mildew is a collective term for various caused by fungi plant diseases usually by a white lining ( fungus grass) occur on leaf surfaces in appearance. A distinction is made between and downy mildews.

The sac fungus ( Ascomycota ) associated with powdery mildew pathogens ( Erysiphaceae ) infest mainly leaves. These are first coated with a flour-like covering, later they turn brown and dry up. The powdery mildew fungi include, inter alia, Blumeria graminis ( affects various cereals and pasture grasses ), or pathogens of powdery mildew of grapevine, Uncinula necator.

The to the Eipilzen ( Oomycetes ) belonging causative agent of downy mildew ( Peronosporaceae ) usually penetrate deeper into the plant and often produce a whitish coating on the underside of leaves. Important plant parasites are downy mildew of wine (Plasmopara viticola ), the blue mold of tobacco ( Peronospora tabacina ) and also relatively host-specific Phytophthora species. Through resistance breeding using poison cos become relatively well known, is downy mildew of lettuce ( Bremia lactucae ).

Powdery mildew: overwintering spores in small enclosures on the plant or as mycelium, eg on the bud scales of fruit trees or on the branches, even on weeds. Dry weather favors the spread ( fair-weather fungus), as well as humid warm weather and the drastic temperature difference between day and night in the fall. A humidity of 70 % is sufficient for the spores, as they are supplied from the house with nutrients and water. Optimal is a temperature around 20 ° for the distribution.

Powdery mildew is not with mildew to confuse another name for honeydew.

Combat

On phlox ( Phlox paniculata ) Powdery mildew is found in veritablem scope nowadays in many gardens. Against the various mildews of different chemical structure in agricultural and horticultural fungicides (eg Tridemorphe ). So pesticides are widespread sulfur-based against the mainly growing on the leaf surface powdery mildew fungi.

As a food source within intact ecosystems of the mildew is vital for some ladybug species. Thus, for example, the feed Sechzehnfleckige and the twenty-two -spot ladybird exclusively by mildew.

Swell

• Plant diseases and pests. In: Meyers Taschenlexikon A-Z. Mannheim 2002, ISBN 3-411-10136-9, pp. 529-530.