Turf Logic - Plant Health Care Program

Plant Health Care Program

Hort-Stories: Phytopthora

Yes, I have a favorite plant disease and yes I realize it makes me a nerd. The disease is phytopthora, which is Latin for plant destroyer. Phytopthora is a strange and fascinating organism that has actually played a role world history.

Phytopthora is an organism that is superficially very similar to fungi. Like fungi. Phytopthora feeds and grows by producing long filamentous structures called mycelium. Although similar to fungi, Phytopthora differs in some fundamental ways. The coolest difference is one that brings into question the lines that man draws between the kingdoms of life. Fungal spores generally rely on chance to disseminate; they are spread by passive means such as the splashing of water, blowing in the wind, or by catching a ride with an animal. Phytopthora however has an active mode of transport. Like an alien species Phytopthora spores lay in wait for weeks, months or years waiting for the perfect conditions to strike.

When the spores find themselves in water and in the presences of compounds produced by plants called root exudates they grow whip-like structures called flagellum to swarm like a horde of locusts toward the source of the root exudates. The spores then penetrate the roots protective sheath. Having breached the plants defenses, Phytopthora�s tentacle-like mycelium spread into the flesh of its victim to suck the nutrients from its still living host. Phytopthora causes a multitude of plant diseases like root and crown rots that can be devastating in the landscape, and in at least one case a disease cased by Phytopthora helped to shape the course of human history.

In the fall of 1845 a mysterious blight began to affect the potato fields of the farmers in Ireland. The blight was caused by a strain of Phytopthora, Phytopthora infestans. Within 5 years an estimated 1 million Irish farmers had starved and a million more had fled. Late Blight as it has come to be known was responsible for one of the worst famines in modern history.

The Irish Potato Famine has become an allegory for the potential dangers of poor farming practices. Potatoes are generally not grown from seed, they are an annual crop that are grown from �seed� potatoes. If you have ever left a potato out for too long you have undoubtedly found that it began to grow �eyes�. If you planted that potato it would grow into a new plant genetically identical to its �seed�. In fact if you cut up, each piece would grow into a plant. This practice was largely responsible for the spread of the blight. Because the plants were genetically identical a disease that killed one plant killed them all. If you are of Irish descent it is likely that your ancestors fled their country due to the action of a strange microscopic organism that blurs the lines between animal and fungi.