Map of an individual Phylloxera “spot” in a Zinfandel vineyard in California
The final Phylloxera map for today stems from an United States Department of Agriculture Bulletin focused on the Phylloxera in California published in 1921. This map indicate the spread of Phylloxera in a Zinfandel vineyard by indicating the state of each individual vine. Thus dead vines are represented by solid circles whereas the varying states of the other vines is indicated by a letter. After looking at the legend, I find it is easy to understand the map. I hope you enjoyed these four different Phylloxera maps.
 Bulletin of the U.S. Department of Agriculture. … no. 901-925 (1920-1921). URL: http://hdl.handle.net/2027/njp.32101050725728