Posted: Wednesday 22 August 2012
by Pippa Greenwood

For some people, ants are a problem simply because they are six-legged and present in large numbers.

Ants and aphids on plant foliage

The arrival of some pests, diseases, weeds and other plant problems can be so regular that they work like a calendar – I can tell where we are in the year from the forum threads on this website, or questions put to me on Gardeners’ Question Time and at garden shows.

But this year, the ants have taken us all by surprise. Usually ants become headline news at the beginning of summer – in June, or sometimes even earlier – but the start of summer appeared to be almost ant-free. Then a few weeks back, they arrived in force, and the ant queries began to flood in. 

For some people, ants are a problem simply because they are six-legged and present in large numbers. My feeling is that if they’re not causing you any particular harm you should try to think of them kindly as six-legged friends and leave them alone. But ants are certainly no fun if you have them in or around your lawn or in areas where you spend time sitting – or even worse, in a favoured spot for eating and drinking. The expression ‘ants in your pants’ only really makes sense when you’ve had them in your clothes and biting.

Ants don’t attack plants, although they are often be found around aphid colonies that produce honeydew as they enjoy the sweet, sticky secretions. But they can cause damage due to their excavations. In the last few days, I’ve had lots of people describe situations where ants burrowing in the soil has caused plants – including sizeable, and often fairly recently planted, trees and shrubs – to wilt and even die. 

In a situation like this, the problem is caused by the ants’ tunnels preventing the roots of the plant from getting in close contact with the soil. The excavations mean that roots are surrounded by air instead of earth, so they cannot take up moisture and nutrients. As a result, the plants suffer. 

So if you are seeing repeated episodes of plant damage caused by ant excavations, or experiencing personal attacks, my favourite solution would be a biological control. Like other biological controls, ant nest nematodes are effective without posing an environmental threat. They need to be watered in – ideally in the evening or in cloudy weather – and the area being treated must be kept moist for 14 days to allow time for them to work, as nematodes are unable to move in dry soil.

But don’t forget to leave a few nests in out-of-the-way places where they are not likely to bother you – after all, ants are a favourite food of the gorgeous green woodpecker.

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Talkback: Ants
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Pepperdog 05/09/2012 at 11:57

I know that ants may be a problem for some people and I suppose it depends where they are in the garden or allotmentt.
I had an ants nest in my leaf-mould bin, it didn't half speed up the time taken to use the leaf mould, and in the bottom were a pair of newts obviously munching on the ants eggs!
So ants aren't all bad and are good for the eco-system

pixie-lady 24/09/2012 at 11:19