Carboxylic Acid Amide (CAA) Fungicides

The mode of action of carboxylic acid amide (CAA) fungicides has in the past been associated with an inhibition of phospholipid biosynthesis, but it has now been confirmed to be an interference with cell wall deposition and cellulose biosynthesis. Pyrimorph is an oomycete-selective fungicide, because it is described to be active against Phytophthora infestans, Phytophthora capsici, and Pseudoperonospora cubensis. Dimethomorph has a good preventive activity, as well as pronounced curative and antisporulant activities. Following a soil drench or foliar application, iprovalicarb is reported to be more systemic than both dimethomorph and mandipropamid. The results of cytological studies have implied that dimethomorph, iprovalicarb, and benthiavalicarb inhibit processes involved in cell-wall biosynthesis and assembly. Although cross-resistance was identified among all CAAs for the vast majority of resistant isolates, as might have been expected, no cross-resistance was found between CAAs and other modes of action, such as phenylamides, quinone outside inhibitor (QoI) fungicides, and zoxamide.