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Help, I've got ants on my plants!

CandideZA
Published on July 10th 2020
20
A close up of a green branch
Ants in the garden often feel a bit like grey territory. On the one hand, they are beneficial insects that play a very important role in maintaining a healthy garden ecosystem, but, on the other hand, they can also cause quite a lot of trouble with their nesting habits and aphid-farming practices. Basically, ants are both friend and foe.
In this article, we take a look at the effects of ants in the garden, as well as how to control them.

Why ants are good

Ants till the soil
Ants, like earthworms, tunnel into the soil to aerate it and to redistribute nutrients. They are also ardent recyclers, they scavenge organic bits and pieces and dead insects, and turn it into natural fertilizer.
Ants naturally control pests
Besides the fact that ants do support some pests (keep reading for more on that), they do serve as a very effective biological control agent. Ants disrupt certain pests by eating their eggs or young. Furthermore, ants are drawn to nectar found on plant stems and sepals and will patrol the plant for threats to these sources, often interrupting pests from feeding or egg-laying.
Did you know? | Indigenous ants protect a number of local butterfly caterpillars.
Ants pollinate flowers
Ants often serve as pollinators as they march to and fro in search of food, unintentionally carrying pollen from one flower to the next.
A close up of a flower
Photo by @Gundula.
Ants disperse seed
Ants are pretty much the gardeners of the Arthropod world, planting seeds in nutrient-rich environments. Some seeds, like Polygala myrtifolia, Agathosma ovata and Podalyria calyptrata, have special ‘fat bodies’ called elaiosomes attached to the seed which serves as a special attractant to ants. Ants collect these seeds to take back to the nest, feed the elaiosomes to their brood and discard the seed in their nesting site underground. These seeds are now protected from predators and removed from fellow competitors until conditions are optimal for germination. If that doesn't convince you to keep ants around, we don’t know what will!
A close up of a flower
Ants help to maintain a healthy ecosystem
Ants are a natural part of gardening. They decompose organic material, aerate the soil, feast on pests and are themselves a light snack for other garden critters like lizards and frogs.

Why ants can be bad

Having a few ants here and there is no cause for concern, however, a concentration of ants might turn on some red lights.
Ants farm aphids
There is one thing that ants cannot resist: sugar. Aphids, and other sap-sucking pests, naturally produce a sweet and sugary substance called ‘honeydew’. Just like humans farm cows for milk, ants farm aphids for honeydew. Very often seen on citrus trees and White Stinkwood, is a black sooty mould growing on the underside of the leaves. This sooty mould is a byproduct of this symbiotic relationship between aphids and ants, with the fungus growing on the honeydew. If you want to get rid of the fungus and the aphids, start with the source and get rid of the ants.
Here are a few posts by fellow gardeners with aphid-farming ants.

jacobus_oosthuizen

Struggling with ants on my lemon tree, eats the ends and effects trees growth. Any suggestions?

brown_chrysanth

#Help white fluffy fungus that ant est on the back of a leave from a lemon tree

vicky

Lots of ants on our Lime tree. Is this a problem or can Ieave them?

A close up of a green leaf
Ants have problematic nesting habits
Ants make their nests in numerous sites in and around the garden, including lawns, pot plants, vegetable or ornamental garden, or in your compost.
  • Lawns | Nesting sites are easy to spot in lawns as ground mounds or hills. Hill building can cause damage to the roots, however, unless the infestation is extremely problematic, the best solution is to learn to live with them. Ants often eat troublesome lawn pests’ larvae and can do more good than harm.
  • Pot plants | Ants in pot plants can cause harmful disturbance of the roots. Giving your pot plants an occasional deep soak should be enough to warn them off.
  • Vegetable and herb garden | If you find ants in your vegetable garden, you do not want to use insecticides or pesticides harmful to your family or pets.
  • Compost | Compost heaps and bins provide ideal conditions for ants to nest. This compost is still usable and once spread into the garden, the colony is disrupted and the ants disperse.

How to control ants

There are numerous species of ants and not all control methods will work for all. Here are a few common ways and recipes gardeners commonly use control ants.
  • Scatter cayenne, cinnamon or chilly pepper around the nesting holes.
  • Mix 15 drops of mint essential oil in a 750 ml water and spray nesting sites and plants.
  • Apple cider vinegar can also be sprayed along trails and on nests, just be careful not to spray your plants.
  • Spot treat ant nests with AnTrap or sticky barriers on tree trunks.
  • Spray organic insecticides like Margret Roberts or Ludwig’s Insecticides or Neem oil.
  • Place food-grade diatomaceous earth (DE) near trail and ants nests. DE is made from fossilized hard-shelled algae (diatoms), a fine powder with a crystal-like shape with sharp edges. It is effective in dehydrating ants, and can also be used for snails and cockroaches.
  • Set up a poison trap using a solution of borax, sugar and water. Although a natural compound, borax is still harmful to humans and pets and we advise this as a last resort.