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Submitted to: Digger
Publication Type: Trade Journal Publication Acceptance Date: 8/1/2014 Publication Date: 9/1/2014 Citation: Grunwald, N.J. 2014. Knowing your Phytophthora. Digger. 9:33-35. Interpretive Summary: Technical Abstract: Phytophthora pathogens are known as some of the most important plant killers known to man. Two particularly notorious killers include the Irish potato famine pathogen P. infestans affecting potato and tomato and the sudden oak death P. ramorum affecting woody ornamentals and trees. Phytophthora pathogens are fungal-like in nature, but are most closely related to brown algae. These pathogens are also known as water molds because they require water for dispersal and infection. Until the emergence of the sudden oak death pathogen in Oregon nurseries and forests, Phytophthora diseases were thought of mostly as root rot or dieback pathogens. Today, we distinguish two major classes of symptoms caused by Phytophthora species on ornamentals (Table 1). The first class includes root, stem or crown rots most often caused by species such as P. cinnamomi, P. cactorum, P. citrophthora and P. plurivora that have been extensively studied. These often result in wilting once the root system is compromised. A second class includes Phytophthora species that cause foliar leaf lesions or stem diebacks. This second disease class is less studied and gained prominence after emergence of sudden oak death known to cause distinct foliar symptoms on ornamentals such as Camellia or Rhododendron. Several species cause foliar symptoms on nursery crops including P. plurivora, P. ramorum, and P. syringae. This article discusses recent research findings and what we currently know about the biology and management of foliar Phytophthora pathogens. |
