From Oranges, by John McPhee:
Some foes [of orange trees] attack underground, most notably the burrowing nematode, a small worm that is the author of a disease called the spreading decline. The nematode feeds on small roots and increasingly cuts off the food supply of the tree, which dies slowly, from the top down, as more and more skeletal branches appear each year and the amount of fruit steadily decreases. When people in Florida are feeling depressed and miserable with some unspecific malady, they sometimes tell one another that they have the spreading decline. Since no one has yet found a way to kill the nematodes without killing the tree, decline brings economic disaster. Whole groves of affected trees and a surrounding margin of healthy trees often have to be bulldozed into a great pyre and burned; after the land they stood on is fumigated, it must be left empty for three years. As we drove along, [the orange grower] Mathias would now and again point to areas full of half-dead trees and say, “Decline.” Some were all but leafless, and looked like Northern apple trees in February. Once, we were on a secondary road, moving along between healthy, thick-foliaged orange groves, when perhaps fifty acres of treeless land suddenly came into view, covered with new houses, all of which looked alike. “Decline,” Mathias explained.