Spring is the time when the weather warms up, and nature springs to life. Fruit trees flower and put out their new leaves ready for the growing season. Sugar rich sap rises from the roots of fruit trees to fuel the new season’s growth.
Gardeners look forward to the beginnings of spring, but so do ants! These little critters keep a hidden stash of aphid and scale insects hidden away in their nests, that they’ve kept safe over winter. They wait till new growth emerges, then take the aphids and scale op to the soft, new growth, so they can such the sap of the tree and exude honeydew, which the ants harvest. The ants actively farm these pest insects, and protect them from beneficial insects that prey on aphids and scale.
Aphids are mobile insects through all their life stages and can move around, but scale insects in their adult stage become fixed in place under a protective, waxy shell.
Sap sucking pest insects weaken fruit trees by reducing the amount of sugars available that the trees require to flower, produce new growth, set fruit and ripen it. They reduce tree vigour and also spread plant viruses, and therefore should be controlled in the garden.
When these sap sucking insects are separated from the ants that guard them, they’re quickly eliminated by beneficial insects such as ladybirds, lacewings, hoverflies and parasitic wasps.
Ants guard and protect aphids and scale from beneficial insects that eat them. Ladybirds love eating aphids!
One way to prevent ants from climbing trees to place aphids and scale on new growth, and to prevent them from protecting any pests that are already up there, is by glue banding fruit trees.
Another way is to use traps which redirect them away from the trees and into baited traps which eliminate them.
How to Build a DIY Outdoor Ant Trap to Protect the Garden and Fruit Trees
One of the easiest ways to protect fruit trees from aphid and scale insect attack is to build an outdoor, rain-resistant ant trap.
This ant trap is my own design and I have been using it for years, it’s guaranteed to work! The design is shown in the labelled photo below.
- One small clear plastic takeaway food container with lid.
- Two cotton balls
- Borax ant bait liquid, to make your own see DIY instructions – How to Make Borax Ant Bait for Indoor and Outdoor Use
To build the outdoor ant trap, follow the steps detailed below.
Step 1. Prepare the container.
Make a few holes on one side of the container, near the lid. Using five holes around 6mm (1/4”) works well. Having only a few holes in one side prevents the rain entering the trap and diluting the bait, which will water it down and weaken it.
Step 2. Add cotton balls.
Place two cotton balls into the container alongside the holes in the side of the container. The cotton balls act as a wick, creating a moist surface that ants can walk on and feed from, without drowning in the liquid below.
Step 3. Add DIY ant bait liquid.
Pour in ant bait liquid so that the bottom half of the cotton buds are submerged, with the top half above the liquid.
Step 4. Seal the container.
Put the lid on the container to keep the rain out and prevent anything other than the ants from getting into the bait solution.
Step 5. Put trap in place.
Place trap near the base of the fruit tree, away from the sun. If it gets too hot ants won’t enter and the liquid will evaporate faster!
After a few hours, ants will find the trap and leave pheromone trails so the rest of them can find their way there to feed on the borax bait.
When large trails of ants appear and head towards the trap, don’t disturb them, allow them to feed. They will take the bait back to the nest and eliminate the problem at the source. That’s how the bait is designed to work!
Since the container is fairly well sealed, very little liquid is lost to evaporation, but the swarms of ants will consume it all down to the last drop. When this happens, wait till the ants have mostly dispersed, then just top up the liquid so that it covers the bottom half of the cotton balls.
If there are too many dead ants on the cotton balls, as pictured below, discard them into the rubbish bin (not into the compost, the borax isn’t good for the soil) and replace them with new cotton balls. Wash out the container with water if it looks too dirty. Continue refilling the trap with borax ant bait liquid until ant activity ceases, then leave the trap in place in case more ants emerge.
By eliminating the ants that farm and protect the pest aphid and scale insects, the pests don’t last very long on the fruit trees.
To quickly eliminate any pests that are on the trees, spray with horticultural oil, but don’t use it on hot days when the weather is 30°C (86°F) or higher, as that may cause leaf burn.
More articles on Garden Pests, Diseases and Problems
Hi Angelo, thanks for this great tip. Seems like it also would work for ants/aphids on soft plants like broad beans? Going to give it a go!
Hi Verity, you’re welcome! It can be used anywhere where ants are farming aphids, including broad beans! 🙂
Is there any evidence to show that diluting a small amount of dish soap and water and spraying directly will affect any growth on fruit or flowering plants?
Will this bait work with leaf cutter ants? (I work in Mexico.)
If leaf cutter ants are attracted to sugar, then it will work on them! 🙂
Hmmm, might not work. They harvest the leaves to feed a fungus that they eat. Strip a tree overnight. I’ll try it on the aphid farming ants, though. Thanks!