One of my favorite stories about pesticides is the story of Bordeaux mix. It’s a story of France in the 1800s (so it must be pretty romantic, right?) and how they were suffering from a shortage of grapes. Don’t feel sorry for them — it was really their own doing. Over the course of the 19th century grape vines were brought from the United States to test their merits against European grapes. It was quickly discovered that, for the most part, American grapes were not the equal of European grapes for winemaking. Unfortunately for the French, however, along with the grapes came a disease: downy mildew. This mildew absolutely ravaged grape vines across Europe, and particularly France from the time that it was introduced, around 1878.
Meanwhile there was another problem for grapes growing in France. People. People like to eat grapes beside the side of the road and so, throughout France’s grape growing regions, grapes on the sides of the road were typically bare. Unlike downy mildew, however, grape growers had a pretty good idea what to do about people. They sprayed nasty stuff on the grapes. This nasty stuff took many forms, but the one which was most effective was a mixture of copper sulfate (basically you dissolve copper in sulfuric acid) mixed with lime. Brushed on a plant’s foliage, it was darn ugly.
Then came 1882; a terrible year for downy mildew. Grape vines were losing their leaves all over Europe, except for those vines beside the sides of the road. There the grape vines were doing just fine. The reason was the copper in the lime/copper sulfate mixture which was eventually dubbed Bordeaux mixture because of where it was first used. Bordeaux mixture is still available today, and is one of the most important tools in the organic grower’s pesticide arsenal. Unfortunately it’s nasty stuff – it builds up in the soil and it’s toxic to earthworms and a wide variety of different plants and aquatic organisms. Using this stuff once in a while – such as once a year – isn’t terrible, but regular use is a good way to ruin your plot of land.
One final thought – Those American vines which originally brought in mildew? They eventually became very important to French wines because of another introduced pest, phylloxera. They were used as rootstocks because they were resistant to this pest — unlike European grapes.