How can they all die so fast and sudden? Wouldn't we expect a certain % to have some immunity, and then those genes pass on and the population eventually recovers?
I read in the book "American Chestnut, The Life, Death, and Rebirth of a Perfect Tree" by Susan Freinkel that when the blight was first discovered in the early 1900's scientists thought that cutting down chestnut trees in the east would stop the blight from spreading. Many trees were cut down that might have had some level of resistance to the blight.
Maybe that might have happened, but panic due to the blight massively increased logging of healthy Chestnuts trees. It wasn't just the blight that caused the ecological disaster; greed and shortsightedness probably played an equal part as well.
Plant immune systems aren't as adaptive as ours, and the American chestnut had no reason to evolve any immunity to the blight because it wasn't present on the continent until the early 1900s.