In a few weeks, these three tough guys have multiplied into zillions of clones, all fungicide-resistant. The next fungicide spray has little effect, and the one after that has no effect. The potato crop turns brown and dies. Arnold and his moldy buddies have won. This scary scenario plays out all too often in the real world.
Fungi are amazingly versatile when it comes to reproduction.
They can manage sex when needed, but they also can make babies by cloning themselves. Cloning, also called asexual reproduction, turns out to be a fast, efficient way to multiply. Speaking of potatoes, a fungal disease called late blight caused the Great Famine in Ireland about 150 years ago. It was one of the first diseases to be successfully controlled with fungicides. Late blight was held in check in much of the world until just a few years ago.