The giant columnar cardon cactus (Pachycereus pringlei) appears to have an ailment(s) that is destroying a large number of plants. The causal
agent(s). whether biotic or abiotic, has yet to be determined. Two forms of symptom development have been recorded. The first is a circular tissue
decay on a branch leading to death of the growing tip. In this case, the dead portion detaches and forms a "flat top" on the living part (hence the
proposed name for this phenomenon). Progressive degeneration and death of the plant ensue. The second form is an initial circular crack on the branch
without decay. Later, the green branch above the crack detaches, creating the characteristic flat top. A third type of degeneration was also
observed: fatal bleaching. The time period between symptoms is unknown. It primarily affects mature, more then 100-year-old plants, but relatively
young plants are also affected. Thirty-six field surveys covering the entire state of Baja California Sur found five major and four smaller
centers of flat top decay. We believe that flat top decay syndrome of the cardon cacti in Baja California is common and widespread.