Some ants are important enemies of insect pests.
However, some ant species cause trouble in the garden and orchard. The most common problem is with ants that feed on honeydew, a sugary sap produced by insects such as aphids, whiteflies, mealybugs, and soft scales. Ants may protect their honeydew supply by driving away these insects' natural enemies. A column of ants marching up and down a tree trunk usually means an infestation by honeydew feeders.