Phytophthora root rot of avocado, a soilborne disease caused by Phytophthora cinnamomi Rands, continues to be devastating to the cultivation of avocados despite more than 70 years of research on control methods. Phytophthora root rot has been estimated to be present in two-thirds of the avocado groves in California, causing losses of almost 30% of the total value of the crop (5). P. cinnamomi m...