Ants in plants

I have ants running around all over my garden. Are they attracted by the sweet smell? Should I let them live in peace or should I exterminate them?
Northern Stoner,
Fort Saint John, BC

The ants are making nests in the planting medium. This messes with the roots. There is a good possibility that the ants are aphid ranchers. The ants eat the aphids’ excreted “honeydew,” which is a sugar concentrate from the plant’s sap. If they are not ranching, they are getting food from another source and that probably has something to do with the garden.

The ants must be eliminated. There is only one thing to do: get rid of them and stop them from returning.

Although it may seem like they are everywhere, once you follow the trails you will probably find that the ants are only colonizing a few containers. If the plants in them are not special, it may be easiest to destroy them to resolve the ant issue.

If the plants are special, then they should be isolated so that the ants cannot get to other plants. A moat can be made using a tray several inches high. Place something like a block of wood
to elevate the pot in the middle of the tray. Add water to the tray and the ants are trapped.

Cinnamon is both repugnant and fatal to ants. As you sprinkle it or water it into the soil you will see the ants scurrying out of their nests. Ants are also susceptible to pyrethrum drenches and other biological insecticides. With a spoon, sprinkle ground cinnamon, which can be purchased at any herb shop or grocery store, on the top of the planting medium. Then make a drench using two rounded tablespoons of ground cinnamon per gallon of hot water. Let the water cool to room temperature then add a liquid pyrethrum insecticide into the solution as directed. A surfactant such as Coco-Wet will make the solution more effective. Use the solution as a drench.

Beneficial nematodes should be added to the medium. These microscopic creatures attack various insects including ants.

To keep the ants out, the perimeter should be lined with an inch wide barrier of dry boric acid. This powder is not a harsh chemical but is lethal to ants should they try to pass through. Cinnamon powder in the garden area, under tables and in out-of-the-way areas keeps the ants away as well.

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