| Abstract: | The use of fungicides in wheat and barley production has increased impressively during the last 10 years in Switzerland. Although no resistance to fungicides has yet been recorded in the field, strategies to delay resistance build-up have been developed. They are the result of collaboration between official research and advisory services. More co-operation is desirable, however, between officials and chemical companies at the level of farmer advice. Our recommendations are based on the following points: 1) minimal numbers of applications; 2) whenever possible, fungicides with multisite action should be used; 3) all components of a mixture should aim at pathogens present to a significant extent in the crop; 4) long-term, flexible strategies. Implementation of these strategies is made easier by several methods for deciding when and whether to treat (EPIPRE; risk evaluation; disease threshold levels). We recommend the alternation of single-site compounds according to their mode of action, rather than the use of mixtures (multi- + single-site, or single-site). A major reason is the common, simultaneous occurrence of a variety of pathogens in cereal crops. Preferring a ‘mixture strategy’ to alternation would imply the use of cocktails of several compounds with possible major disadvantages such as cost, residues, and iatrogenic diseases. |
