Microorganisms have many roles in nature. They may act as decomposers that obtain nutrients from dead materials, while some are pathogens that cause diseases in animals, insects, and plants. Some are symbionts that enhance plant growth, such as arbuscular mycorrhizae and nitrogen fixation bacteria. However, roles of plant pathogens and diseases in natural ecosystems are still poorly understood....

This paper reports on five years of observations in a case-control study examining the role of tree and site factors on the development of Phytophthora ramorum stem canker (sudden oak death) in coast live oak (Quercus agrifolia) and tanoak (Lithocarpus densiflorus). In September of each year from 2000 through 2004, we collected data on P. ramorum symptoms, tree condition, midday stem water pote...

Effective control of plant disease remains a key challenge. Eradication attempts often involve removal of host plants within a certain radius of detection, targeting asymptomatic infection. Here we develop and test potentially more effective, epidemiologically motivated, control strategies, using a mathematical model previously fitted to the spread of citrus canker in Florida. We test risk-base...

Pitch canker, caused by the fungus Gibberella circinata (anamorph = Fusarium circinatum), was first identified in 1945 as a disease of pines in North Carolina (7). Pitch canker now occurs throughout the southeastern United States where it remains a chronic problem in plantations, nurseries, and seed orchards (2,3). In California, a pitch canker infestation that was first recognized in 1986 has ...