Fungus does frequently follow a wound of some sort which I suppose either 1. allows the tree to succumb to fungus present in the soil as it is weakened. or 2. allows fungus to enter the tree through the wound itself. Again I would think there are different kinds. IF it is the result of a wound, it may not affect the soil and planting another tree there would be ok. But again you wouldn't really know without some way of testing the soil first. Crabapples can be really pretty trees, but many people do not prune them properly and they look like a bush on a stick and are too low to the ground ect. The variety can make a huge difference as well. I have a crab apple that has small berry-like gold colored fruits and they stay on most of the winter. It is very attractive. I do have one in my front yard that has purple foliage year round and it is really nice. They like water, so in drier areas, they may tend to look not as nice during the hotter months. They are nice trees for town yards because they do not overwhelm smaller yards. Suitable subs are dogwood, redbud, other fruit trees, ornamental fruit trees such as cherries, or holly. of course if space is not a problem you can plant anything as long as the soil is ok.
