Phytophthora ramorum

Plant Damange:

Foliar leaf spots and shoot blight. Bleeding stem cankers on some members of the oak family.

Multiple Hosts:

  • Camellia (Camellia)
  • Pieris (Pieris)
  • Rhododendron (Rhododendron)
  • Viburnum (Viburnum)
  • many others


This federally quarantined pest is regulated to prevent its spread in North America. It is found in natural landscapes along the north and central California coast and in a small area on the southern Oregon coast. It has been found in a few West Coast nurseries following inspection.


Spores landing on wet leaves or shoots germinate and infect the plant. Young leaves are especially susceptible. This disease is favored by moderate temperatures and moist conditions. It is spread by airborne and rain-splashed spores. Moving infected plants can spread the disease over long distances.


Several spore types produced by this pathogen could help it survive extreme hot and dry conditions.