Phylloxera is a bug that feeds on a vine's roots. It is an aphid native to North America, and its effect on wine production is legendary. In the 1860's phylloxera managed to make its way over to Europe and proceeded to devastate European vineyards. In much the same way that Europeans brought viruses that Native American's immune systems were unprepared for, the European vines had no natural resistance to Phylloxera. As a result, almost all European vineyards were completely destroyed, and an international effort to restore wine production started. French wine production in particular at one point was thought to be completely lost.
Fortunately, someone discovered that the good old American table grape vines, vitis labrusca, were unaffected by phylloxera. American rootstock was then sent to Europe, and the vitis vinifera vines were grafted onto the labrusca rootstock. To this day almost every single vine planted in the world is grafted in this way. There are only a few places, mostly in South America, that have escaped the effect of these deadly bugs.
When I heard the story of phylloxera, my first thought was, does the labrusca rootstock affect the taste of the grapes and therefore the wine? Apparently it doesn't. While the labrusca grapes make terrible wine, apparently the roots are virtually identical. There are actually a few benefits to this little bug. Before anyone understood phylloxera, wine production (good wine, anyway) in the United States was non-existent. Thomas Jefferson had famously brought back many vine clippings from France to try and plant at Monticello, and was totally unable to produce any grapes. No one understood why that was until they discovered that it must have been the phylloxera that was eating Jefferson's vines. So as a result of this bug, and the international cooperation it necessitated, we have wine in the United States. Hooray for us!