Oxalic acid vaporization has been used in European countries for many years but until recently it was illegal in the United States. Oxalic acid is a naturally organic chemical found in plants and used as a defense mechanism against herbivores. Oxalic acid was registered as a pesticide in 1957 and works to break down the varroa mites exoskeleton system. Vaporization is one of the easiest treatments on the market as it does not require breaking apart the colony to treat. Studies have shown that oxalic acid has a 95 % kill rating in a broodless period in hives.