Powdery Mildew

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powdery mildew

[′pau̇d·ə·rē ′mil‚dü]
A fungus characterized by production of abundant powdery conidia on the host; a member of the family Erysiphaceae or the genus Oidium.
(plant pathology)
A plant disease caused by a powdery mildew fungus.

Powdery Mildew


any one parasitic fungus of the order Erysiphales (Perisporiales) of the class Ascomycetes. The multicellular mycelium usually develops ectotrophically, on the surface of various plant organs. It rarely develops endotrophically, in the cells of leaf parenchyma, or mesophyll (in the genera Leveillula, Phyllactinia). The fungi feed by means of special outgrowths of the mycelium, or haustoria. During the vegetative period, they reproduce asexually by means of conidia. The fruiting bodies, or cleistothecia, develop most often on aging mycelium; they are dark in color, lack stomata, and have hyphal processes (whose structure has species or generic specificity). The cleistothecia have one or more sacs (asci), which form as a result of the sexual process.

There are 20 genera of Erysiphales, including about 100 species. They prefer dry places and are especially abundant during a dry summer. The mycelium forms a white coating on the green parts of a number of wild and cultivated grains, causing the disease powdery mildew. Species of fungi that cause powdery mildew of oak, grape, hops, apple, and other plants are widely distributed.


Powdery Mildew


(also oidium disease), any one of a group of plant diseases caused by powdery-mildew fungi (Erysiphales). Powdery mildew usually appears at the beginning or middle of summer in the form of a powdery, cobwebby, or tomentose mealy-white film that spots leaves, shoots, stems, petioles, fruit stalks, and sometimes fruits. The film gradually spreads, covering most of the green organs, which become brownish with innumerable black spots. Diseased leaves and shoots become fragile and wither prematurely. The wood of trees and shrubs infected with powdery mildew does not mature; as a result, the plants freeze in the winter. Those shoots that remain alive exhibit poor growth in the next vegetative period. Sick fruits usually split; the flesh is exposed and quickly rots.

All the causative agents of powdery mildew are exoparasites of plants. Many powdery-mildew fungi are parasites of agricultural crops. The most harmful species are Uncinula necator, which parasitizes grapes; Sphaerotheca mors, which infests gooseberries; Erysiphe graminis, which parasitizes bread grains; Sphaerotheca pannosa forma persicae, which affects peaches; Erysiphe communis, which infests sugar beets; and Sphaerotheca pannosa forma rosae, which parasitizes roses.

Control measures include destroying affected plant residue, pruning and burning diseased shoots, deep autumn plowing, applying phosphorus and potassium fertilizers, using crop varieties that are more resistant to powdery mildew, and spraying or dusting plants with sulfur preparations or with dinocap (kara-thane). Sulfur preparations are not used on gooseberry, since they cause shedding of leaves. For control of powdery mildew on roses, sodium carbonate or a solution of green soap may be used.


Golovin, P. N. Muchnistorosianye griby, parazitiruiushchie na kurturnykh i poleznykh rasteniiakh. Moscow-Leningrad, 1960.


References in periodicals archive ?
For example, some seedlings in Cornell's "no-spray" block show remarkably few powdery mildew colonies on their leaves, but only now are we learning what gene or genes are associated with the observed resistance.
Two trials were undertaken during the 2016-17 season to determine the best fungicide management strategy for the control of powdery mildew using different fungicides on the variety Jade-AU, and using different row spacings.
All the recommended package of practices was applied except protection for control of powdery mildew under natural filed condition.
Wheat powdery mildew is caused by the Erysiphe graminis, which often infects the leaf blade and sheath.
15], demonstrated that powdery mildew thrives well at 16-28[degrees]C but temperature for conidial germination is 20-24[degrees]C.
Not preferred by squash bugs but susceptible to vine borers and powdery mildew, delicata squash (C.
The objectives of this study were (i) to estimate the DFE for the multiple pathosystem of barley brown spot and powdery mildew using the critical-point and experimental parcel models relating the disease intensity to the grain yield, and (ii) to determine the EDT using the model-generated damage coefficient from the DFE.
Powdery mildew fungi produce microscopic air-borne dispersal spores with an unusually high water content, enabling them to infect underdrier conditions Some asters, surprisingly, are unaffected by mildew, the elegant, willowy six-footer, Climax, with panicles of powder-blueflower heads one these.
She also looked at how well 12 different genotypes of the same asexual evening primrose species weathered attacks by powdery mildew.
For the past 8 y, we have observed increases in the incidence of a naturally occurring powdery mildew fungus on garlic mustard in southwestern Ohio that we initially identified as Erysiphe cruciferarum Opiz ex.
Anthocyanin coloration of the tip was the main discriminant variable for powdery mildew.