Gardening in Spain- What do I do about ants in the orange tree?

Help, There are ants in my orange tree. What can I do to stop them?

This question came in today from a member of the gardening club whose neighbour was in a panic about the number of ants climbing into his orange tree.

The likelihood is that these ants are not particularly interested in the orange tree itself, theyre far more likely to be interested in something else thats in it, and at this time of year thats probably aphids.

This autumn has been warmer than average with a spell of intense rain, creating  perfect breeding conditions. Citrus trees are particularly prone to aphids , so look carefully at the leaves to see if theyve got the telltale signs of a black, sooty looking deposit anywhere, which is a giveaway sign to indicate the presence of this unwanted pest.

They excrete a sweet, sticky goo, called honeydew, which drops onto the leaves below where theyre most active, so look underneath the leaves to see if theres any sign of them.

Ants love honeydew and feed on it, also feeding on the aphids themselves, literally milking them for the honeydew. Remarkable research has shown that ants "farm " aphids, sometimes even nipping their wings to prevent them moving too fast and excrete a chemical  substance through their feet which slows down the reactions of the aphids, making them more docile, sometimes literally herding them to the freshest growth on a plant. There are documented cases of aphids being carried off to ant colonies for food or for continued honeydew production, and ants love anything sweet and sugary, so theyre not really interested in the tree, its the aphids theyre after.

There are several approaches that can be adopted:

1. Get rid of the aphids

In mild cases, trees can be sprayed with a mix of washing up liquid and water , or a garlic and water infusion, (1 pint boiling water, 3 crushed cloves of garlic left to infuse) but for more severe or persistent infestations, chemical controls are most effective. These are easily obtained from agricultural suppliers, the main ones dispensing with aphids, spiders and other pests in one application.

Organic controls are becoming more widespread in the region, but are still a longer-term option.

1. Stop the ants going up the trees.

Ants leave a pheromone trail that can be followed by other ants. Break the pheromone path and theyll stop going up the tree.

There are several ways to do this, depending on whether you wish to simply divert them or get rid of them altogether.

They wont cross lime or chalk , so create a barrier. One of the simplest home solutions is to use talcum powder, pour a ring around the base of the tree and thats the end of it, or if you have chalk, draw a thick ring either around the base of the tree or on the trunk.

Visitors to Greece will have noticed the bases of the trees are whitewashed, theyre actually lime washed for this very reason.

Other organic solutions are to create a barrier on the treetrunk that the ants wont cross. Surprisingly, Vaseline in a thick ring around the base of the tree will stop them going up, or you can buy chemical strips , which are secured around the base of the tree and form a protective barrier.

Duct tape , taped around the tree sticky side out is also an effective barrier.

To get rid of the ants altogether, there are various chemical powders available, but be careful if there are children or pets around- a lot of these things are pretty lethal.

Boiling water is another solution, but only if you dont suffer from guilt.

To deter ants from coming into the house, use scents that they hate - garlic, peppermint, camphor, tansy, cinnamon and crushed peppers are all a big turn-off , so dab peppermint oil or raw garlic at entry points, and believe it or not, theyve got a real problem with cucumber, especially sliced up and left where they are crossing.

( Dont use cake making peppermint or peppermint cooking products, buy peppermint oil from health shops instead.)

So theres your answer, clear whatever is attracting the ants away and theyll go off in search of something else, so if its not aphids, it could be the fruit theyre after, theyve got a taste for sweetness and sugar, so practice good husbandry, clear old fruit from branches and just be vigilant, act the moment you see them in your orange tree as theyre a symptom of a greater problem.

And remember, theyre not all bad, they do aerate the soil and pollinate plants, just keep their numbers under control and theyre a useful ally in the garden.