Cactus
Fungi, bacteria and viruses attack cacti, the first two particularly when plants are over-watered. Fusarium rot can gain entry through a wound and cause rotting accompanied by red-violet mold. ""Helminosporium" rot" is caused by "Bipolaris cactivora" ( "Helminosporium cactivorum"); "Phytophthora" species also cause similar rotting in cacti. Fungicides may be of limited value in combating these diseases. Several viruses have been found in cacti, including cactus virus X. These appear to cause only limited visible symptoms, such as chlorotic (pale green) spots and mosaic effects (streaks and patches of paler color). However, in an "Agave" species, cactus virus X has been shown to reduce growth, particularly when the roots are dry. There are no treatments for virus diseases.
San Andreas Creek
Fog drip may play a key role in the precipitation in the upper watershed. On Cahill Ridge (just west of San Mateo Creek and east of Pilarcitos Creek, at an elevation of , Oberlander measured fog drip beneath tanoak ("Lithocarpus densiflorus"), Coast redwood and three Douglas fir trees, the latter tall. He found that the trees most exposed produced the most precipitation and in five weeks of measurement (July 20 – August 28, 1951) fog drip below the tanoak produced of precipitation, more than the total annual precipitation on nearby grasslands and chaparral. The Douglas fir produced of fog drip and appeared to provide unique conditions supporting the orchids giant helleborine ("Epipactis gigantea") and phantom orchid ("Cephalanthera austiniae"), since these plants were found exclusively in these moist ridge tops.