A Technical Report from The Bartlett Tree Research Laboratories
Leaf and twig blight on holly (Ilex spp.) is a fairly common disease in the Pacific coastal region of Canada and the northwestern United States. This disease is caused by a fungus-like organism called Phytophthora ilicis. There are many well known pathogens in the genus Phytophthora, most of which cause root rots or trunk cankers, including the ‘Sudden Oak Death’ pathogen P. ramorum. Phytophthora species require free water (either in the soil or on the plant surface) to complete their infection cycle as they have motile spores that swim to new host tissue and infect. Excess moisture is, therefore, an important factor in any Phytophthora disease situation.