 The next group we're going to discuss are the cankers on the list, and the first one is nectria canker. Nectria canker is actually a number of different fungi that cause these cankers, but what's unique about these is the fungus gets in on a branch stub, and we can see here on this oak here, the fungus got on the branch stub, and there's an interaction between the tree and the fungus. The fungus kills a little bit and then the tree grows around it. The fungus kills a little bit and the tree grows around it. So actually what you can do is we get these target-shaped cankers, and we can actually count how many years the fungus and the tree have been interacting, and what happens is it causes these target-shaped cankers. When you see this target shape, it's a nectria canker. So this is a very good example. Again, here's another good example, a branch stub. You can see the number of callus tissues that just tried to get rid of the fungus. Again, here's another sample, a branch here, and you can count how old the fungus and the tree were trying to kick each other out. Here's another example. Again, the fungus got on the branch, and you can count how many years that the tree has tried to get rid of the fungus. All nectria cankers will cause these target-shaped cankers. A canker, in this particular case, is what we call the death of the cambium. The fungus has killed the growing part of the tree, and the tree is trying to get rid of it, and by doing that we get these circles and these targets. This is a nectria canker.