Metabolization by Fungal Esterases

Although early studies on the resistance risk of Qols had detected a multitude of mutations aU lowering the sensitivity to Qol fungicides, up to now, besides the G143A mutation, only one further mutation could be proved in field isolates. At 

Practical Importance of Individual Resistance Mechanisms to Qols 

Early (pre-launch) risk assessments were essentially not able to predict correctly the high resistance risk of Qol fungicides. This rehects a general problem with mutagenesis studies delivering mostly only limited informahon on the impact of a mutation on htness and competitiveness. 

Besides the intrinsic properties of each resistance mechanism, the economic impact of Qol resistance on the Qol market is also governed by the availability of alternative fungicidal modes of action for disease control and resistance management in each crop. For example, the early and rapid development of resistance of cereal powdery mildew (Blumeria graminis) in European wheat and barley production from 1998 on had a remarkably low impact on Qol consumption. The broad disease spectrum controlled by Qols and the availability of several other modes of action for the control of powdery mildews in cereals such as DMIs, amines, cyprodinil, quinoxyfen, and metrafenone resulted in a nearly unchanged use frequency of Qols in European cereal production. 

Adapted from FRAC Qol Working Group (www.frac.info). 

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