http://www.woodvinegar.org/history.html
Modern research on the use of wood vinegar was first carried out in Japan in the early 1950s. It was reported to be effective against: rosette or green mosaic in wheat, nematode in sweet potato, tobacco mosaic, powdery mildew in leafy vegetables, leaf miner and other insect pests. However, due to the introduction of agro-chemicals and their instantaneous effects, research on wood vinegar took a back seat. Ten years ago, interest in wood vinegar resurfaced as the effectiveness and safety of agro-chemicals were put on the spot. It is now commonly used by Japanese farmers and is also catching up fast in Taiwan and Korea.
The various elements in the wood vinegar work as co-enzymes or catalysts. Various enzymes are involved in reactions such as cell multiplication. The functions of the enzymes are assisted by the elements in the wood vinegar which co-ordinate the reactions and the cell multiplication. Elements that are effective as co-enzymes and catalysts require only a minute amount. It is like vitamins in our bodies. The dosage of some of these elements is effective in the unit of PPM. (Parts per million).