In the home orchard or yard, a crabapple tree can be planted along with more desirable apple varieties to cross-pollinate the trees or as a landscaping plant for springtime flowers. But some home owners despise crabapple trees for their susceptibility to disease and pests, including apple scab, mildew, fire blight and Japanese beetles. If you have a crabapple tree, you may wish to kill it completely before removing it from your landscape to prevent tiny crabapple saplings, called suckers, from springing up from the tree's roots or stump. Killing a crabapple tree is simple.
Cut a groove around the circumference of the tree with an axe. This groove should extend 1½ inch into the tree trunk and should be at least 2 inches on smaller trees and up to 8 inches on larger trees. This process is called girdling a tree. Girdling a tree interrupts the flow of sap from the tree's roots to the top of the tree. This kills the tree.
Mix 1 part systemic herbicide containing triclopyr and 1 part water. Pour the solution into a spray bottle.
Spray the herbicide and water mixture onto the groove cut in the tree until the groove is saturated with moisture. Although girdling itself will slowly kill a tree, spraying a systemic herbicide will speed up the process and cause the tree to pull the poison down to its roots, which will kill the tree's roots and prevent suckers from forming.
Cut a second ring into the tree approximately 3 inches above the first girdling ring and reapply the herbicide. A second ring is not required for girdling, but will make an application of systemic herbicide more effective.