As with most garden myths, there’s a kernel of truth, so let’s pull it apart and deal with it properly.
The Truths:
Yes, ants farm aphids for their sweet honeydew. So in theory, if you control the ants, you reduce the aphid population. And yes, Vaseline has been used as a physical barrier to stop ants climbing.
The Reality:
Smearing Vaseline directly on your tree’s trunk, especially thin-barked trees like citrus or stone fruit, is a fast track to disaster. Petroleum jelly (Vaseline) suffocates the bark, traps moisture, and can cause ringbarking. With no application rate, no guidelines and just guesswork, that can kill your tree.
What should we do instead?
First, let’s talk about what’s really going on.
Excess ants usually (not always) point to hydrophobic soil. Soil that’s either not getting enough water or repelling it altogether. Ants love this. They build their nests in the dry root ball and actively repel water to keep their home dry. That means your plant stays dry too, stressed, weak, and vulnerable.
Then come the aphids, followed by scale and mites. Now the ants have a buffet and the whole thing snowballs.
Fix it this way instead:
Drench the soil with a soil wetter, really soak it. This floods out the ants and starts restoring water flow.
Follow up with a complete fertiliser like Organic Link to support recovery.
Start a pest management routine: Spray fortnightly with something organic like neem or Eco-fend.
Add a liquid feed (like Plant Care) every two weeks for a month to boost vitality and immunity.
It’s not instant but this approach is safer, more effective, and kinder to your trees in the long run.