Pest of the Month October 2010 – Algal Leaf Spot

Cephaleuros spp.

  • Hosts:  Guava, magnolia, coffee, avocado, mango, breadfruit, coconut, cacao, citrus, and others
  • Distribution: Tropical and subtropical climates and on all continents and probably all islands between 33°N and 33°S of the equator where temperature and humidity are suitable for growth.
  • Symptoms:  For C. virescens,  leaf spots on the upper leaf surface, raised and velvety in shades of orange or brown.  For C. parasiticus on guava, bright but relatively sparse orange spots on the undersides of leaves causing full-thickness necrosis.
  • Spread by:  Wind and splashing water
  • Management:  Sanitation (removing/discarding infected leaves), pruning overhanging trees to reduce relative humidity, reducing plant stress, controlling weeds around affected plant, application of some fungicides (Bordeaux mixture), selecting resistant varieties

Source: Cephaleuros Species, the Plant-Parasitic Green Algae by Dr. Scot Nelson, University of Hawai’i at Manoa, College of Tropical Agriculture and Human Resources Cooperative Extension Service Plant Disease PD-43, August 2008

Algal leaf spots on avocado. Photo by Dr. Scot Nelson, UH CTAHR