ABSTRACT
Powdery mildews are spread over great distances by wind and can be moved around the world on plants with inconspicuous or latent infections. Within the powdery mildew family, Erysiphaceae, some members have very narrow host ranges, whereas others have broad host ranges and affect plants in multiple plant families. Powdery mildews differ from the vast majority of other fungal pathogens in that, with few exceptions, the mycelium grows superficially over host tissues. Only specialized feeding cells, called haustoria (Chapter 7), invaginate the host epidermis (Figure 12.3). Powdery mildew life cycles (Figure 12.4) are entirely biotrophic. No species has been grown in axenic culture apart from its host for any significant duration, and none can grow on dead plant material.
