What is Phytophthora?

Phytophthora species (Phytophthora spp.) are a group of fungi-like microorganisms that attack plants. They’re commonly known as “water molds” because their spores can travel through water to infect new individuals (hosts).

The name, “Phytophthora” means “plant-destroyer” from its Greek roots, which gives an idea of how destructive this disease can be.

There are over 150 different species of Phytophthora that have been identified/described, and there is likely more that have been undiscovered! Some species have specific hosts that they infect, whereas some others (e.g. Phytophthora cinnamomi) attack many different species of plants.

It was first discovered as the Irish potato famine in the 1800’s, which was accidentally imported on potatoes and eventually exterminated the majority of potato crops.

Today, we have discovered numerous diseases caused by Phytophthora that have proven to be detrimental to forests and agricultural crops across the globe. Examples of such include sudden oak death, European oak decline, and many forms of root rot, fruit rot, and pod rots (e.g. of Cacao).


History of one of the globes smallest killers
Potato blight is caused by Phytophthora infestans. The pathogen originates from Mexico and accidentally came to Europe together with imported potato plants. During the 1840’s the disease on potato spread rapidly in Europe, at first with no one really knowing what it was, and caused a catastrophic mass starvation in Ireland where potato were the main staple for many of the poor. Today, Phytophthora infestans is still the worst threat to potato farmers.