ABSTRACT
Ammonium thiocyanate was first introduced as a soil-applied herbicide. The fact that 2, 4-d is a hormone weed-killer and, therefore, interacts with natural indole-3-acetic acid (IAA) present in the plant does make the specific IAA-thiocyanate reaction relevant when assessing the success of the treatment. The combination of ammonium thiocyanate and amitrole is claimed to be one of the few truly synergistic reactions between herbicides. Work carried out at Glasgow on the eradication of bracken comparing amitrole alone with the activated form revealed a much improved performance with activated amitrole compared with amitrole alone. The studies on the effectiveness of a range of free radical inhibitors in amitrole formulations led to a particular interest in the behavior of iodide in plants. The behavior of thiocyanate in plants is particularly interesting in that its oxidation to the toxic moiety does not take place as readily as with iodide, and the interaction of thiocyanogen with IAA may possess something of a selective nature.
