Although the use of chemicals or fungicides to control plant diseases can be traced back as far as 1000 B.C., it was not until the 1930's- 1960's that substantial efforts were devoted to the development of non-corrosive and non-phytotoxic fungicides. Among the first of the "modern" fungicides were the dithiocarbamate fungicides such as thiram, maneb, and zineb. These materials have broad-spectrum activity but are contact, protectant fungicides. Dithiocarbamate fungicides were used for control of field crop diseases and there still are several formulations labeled for use on field crops. Their use has declined because they are protectants that need to be apply prior to disease development or at the first sign of disease development and because as contact materials they are subject to weathering and may need to be reapplied if weather conditions remain favorable for disease development.