Multi-site fungicides

Although some multi-site fungicides have been in use for over 200 years, resistance reports for this class of chemicals are rare and usually of low practical importance. As shown in Table 12.5, resistance of cereal pathogens to organo-mercury compounds was reported in 1964 and resistance of apple scab to dodine in 1969 [5]. 

Other multi-site of action organic fungicides include dichlorofluanid, anilazine and chlorothalonil. 

When benzimidazoles are abused, resistance is likely to occur and often has. However, when used judiciously as part of well considered strategies, benzimidazoles continue to give excellent control. Mixtures and combinations of mixtures and alternations with multi-site contact fungicides have proved very effective, especially if used before problems become apparent. 

Forty-six different specific fungicide and bactericide modes of action are actually classified in the FRAC lists [3], including the unknown modes of action (Table 12.1). In addition, numerous multi-site inhibitors and plant defense inducers are available for the control of plant diseases worldwide. Therefore, a sufficient diversity of modes of action seems to be available for the control of plant diseases and for an effective resistance management. However, many fungicides are only available in a restricted number of regions and crops because they may not be registered everywhere or because the market size may not be big enough. 

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