Thiocarbamate fungicides: reliable tools in resistance management and future outlook.

Among contact fungicides, dithiocarbamates have remained successful and are used worldwide. These organic sulfur fungicides, viz. mancozeb, maneb, zineb, ziram, thiram, metiram and propineb, have helped growers manage several economically important plant diseases. Their multi-site mode of action and broad-spectrum disease control make them some of the most common partners in mixtures of a number of single-site fungicides as part of resistance management strategies. Indeed, it was the part played by ethylene-bis-dithiocarbamates such as mancozeb in delaying the evolution of phenylamide resistance in several oomycete phytopathogens that laid the groundwork for mixture strategies to become a cornerstone of anti-resistance management in plant disease control. Dithiocarbamates, however, do not have systemic action, are only surface protectants and have to be applied prior to pathogen infection. Dithiocarbamates will likely continue play a key role as reliable resistance management tools to prolong the efficacy of single-site fungicides. The primary metabolite ethylene thiourea produced by some of these fungicides is considered a reproductive and endocrine disrupter in animals. Therefore, dithiocarbamates need to be used at reduced rates or in slow-release formulations.