When applying systemic pesticides to trees, spray bark or drench or inject soil whenever possible, as directed on product labels, instead of injecting or implanting trees with pesticide. Injecting or implanting trunks or roots injures trees and creates wounds that can provide entry sites for pests. Unless tools that contact internal parts of trees are cleaned and disinfected when treating multiple trees, contaminated tools can spread certain bacterial, fungal, and viral pathogens from one tree to another.