Common ants do not typically infest healthy plants. If you notice ants climbing on your plants they are probably attracted to a source of food provided by some other agent such as pests or disease. It is suggested you closely examine the underside of younger leaves towards the growing tips of the plants. There is a good chance that you will find that the leaves and soft stems are sites where sap-sucking pests such as aphids or whiteflies are feeding and reproducing. These sap feeding insects have specialized mouth parts called stylets that are hollow needle-like tubes, which the insects use to pierce the outer layer of plant leaves and stems. The sugar produced by leaves is transported around the plant in vessels in young leaves and shoots. This sugar, found in a dilute syrupy liquid, is literally pumped around the plant as the result of a slight pressure. When an insect stylet pierces the sugar vessel, the liquid is then pumped into the digestive system of the insect. Excess sugar liquid that cannot be absorbed by the insect (also known as “honeydew”) is left behind. Honeydew contains a significant amount of sugar. Ants have the acute ability to detect sugar in the environment using their antennae. Bugs that feed on plant sap such as aphids etc., provide ants with a direct avenue to access sugar made by plants and found in honeydew. Ants visit the feeding sites of these bugs to take advantage of the excess sugar liquid or “honeydew.” Ants also help protect the sap-sucking bugs from other predators to ensure their own continual supply of honeydew.
So what do you do next? First, assess the extent of the problem by carefully examining your plants. If you can live with the problem, simply continue to monitor the situation. If the problem grows, you may want to take one or more of the following actions: physically remove the bugs, introduce natural predators (ladybugs), or treat the plant(s) with insecticide.