Crabapple trees are susceptible to a bacteriological disease known as fireblight, which can be spread by pruning. Therefore it is important that you only prune your crabapple in the winter or early spring, while it is dormant and before the tree shows signs of new growth. Pruning tools should be soaked in a solution of bleach and water in order to prevent the spread of any disease.
Remove all dead or diseased wood. Take your time and make certain that you have found all dead wood. Tap on branches with something hard to assess their soundness.
Remove any branches that are growing downward or rubbing against each other.
Remove all branches which are growing sideways through the canopy. This helps open the canopy and allows more light and air into the center of the tree. Never remove more than 25 percent of a tree's branches during any one pruning.
Remove any suckers that are growing from the roots or from the trunk. Suckers have a smooth skin, not bark like the rest of the tree.
Discard all wood or burn it to prevent the possible spread of fireblight or other disease.