Plant Doctor Archive

Ants everywhere

HAVING recently moved house I am renewing my garden. Unfortunately, every plant, and now my pots, are full of ants. They are all over my roses. I have tried spraying but to no avail. I am at my wits end. Can you help?

ANTS crawling up the stems of roses and other garden shrubs are usually a sign that aphids, scale or other sap-sucking pests are present. Sap suckers excrete sweet honeydew which ants love to feed on and take back to their nests for their young. If you get rid of the sap suckers, the ant problem on the plants should also disappear.

There are lots of effective products you could use to control sap-suckers on roses, such as Nature's Way Insect Spray, Confidor, or any of the pyrethrum-based insecticides like Garlic & Pyrethrum.

Once they make their homes in potting mix, ants can be a little harder to get rid of. Bear in mind they only move in if it's relatively warm and dry, so more regular watering might be enough to make them pack up and go elsewhere.

If that doesn't work, watering a solution of pyrethrum insecticide into the mix should do the trick. Or, if it's practicable, you could repot your plants into fresh mix.

As a last resort, sprinkle a small amount of diazinon granules (available as Soil Insect Killer or Lawnguard Prills) on to the surface of the mix and water in - but be aware, the potting mix and water draining from the pot will be contaminated for perhaps 2-3 weeks until the insecticide breaks down.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.