ABSTRACT
The barley mildew pathogen, Erysiphe graminis f. sp. hordei, responds rapidly to almost all host resistance genes and fungicides, particularly if their commercial introduction is rapid and on a large scale. However, the pathogen population on each variety or fungicide treatment tends to be adapted to that particular control measure and is usually less well-adapted to other hosts or fungicides. The inability of the pathogen to become highly adapted to many different components of control simultaneously can be exploited in crops in which adjacent plants are either of different varieties or are treated with different fungicides. In such mixtures, the distance between identical plants, or identically treated plants, is greater than in a conventional crop stand, which helps to slow down the spread of the pathogen.
Mixing of varieties or of fungicides can be integrated in various ways. One of the simplest and most advantageous appears to be fungicide treatment of the seed of a single component of a three variety mixture. Yield is not less than that from a conventionally treated mixture, but cost, selection for fungicide insensitivity and environmental contamination are all reduced,
