The only problem I get with ants is on cherries, because I get rid of the aphids on other crops by spraying with an aphicide and therefore the ants go elsewhere for sustenance. But the problem with cherries is that when the fruit is nice and ripe, the ants crawl up the tree and suck them dry.
Given a reasonably dry summer, sprinkling an ant eradicant around the base of the tree and any supporting mechanism is very effective. Ants do not survive to reach the fruit.
If you object to the use of chemical sprays, an old and very effective eradicant is a soft soap spray. This was available in Garden Centres, but now replaced by the much more expensive insectidal soap. However, soft soap is also sold by plumbers’ merchants (used in seating the exit pipe of WC’s).
Although ants can sometimes be a nuisance I find that I can use them to my advantage as they will show me where either aphids or possibly scale insects are lurking early in the year, which allows me to spot spray them. Very little spray is then required though a later check is advisable for any missed.
The removal of the first aphids can prevent a possible loss of apples as the rosy apple aphid, otherwise known as blue bug, which is how they appear initially. will cause stunted apples and destroy the branch tips if unchecked. Unlike greenfly, they often hide under the lower leaves which being softly curled makes them difficult to find.
The best solution to this problem I know is to use a barrier of non-setting glue to trap the ants as they move up the trunk and so preventing them gaining access and laying a scent trail to guide other ants to the aphids. This acts rather like a horizontal fly-paper.
In the USA the product is sold as ‘Tanglefoot’, but this does not appear to be available in the UK. Some time ago I bought a small tube of ‘Agralan Insect Barrier Glue’ which I guess is much the same sort of product but I have not seen it in the shops lately so perhaps it has been withdrawn? Agralan still do commercial size tubes of barrier glue that fit into a mastic gun but you would have to check with them if it is possible to get hold of the product in small quantities. Both http://www.tanglefoot.com and http://www.agralan.co.uk give more details.
When applying barrier glue it is best to put a band of tape (either masking or PVC) around the trunk and squirt the goo onto that. This allows the barrier to be cleanly removed and replaced from time to time. The other thing is to make sure you also treat any support stakes too, otherwise the ants soon discover any alternative safe way into the canopy.
Thank you for this great info on ants – I knew they were doing something to my cherry tree as the marked fruit did not look like bird pecking. Now I know that the ants were sucking the fruit – thus releasing a sticky coating on the fruit? As I pick it off the tree all the fruit becomes sticky. I will be putting some ant trap stuff around the base.
The way I control ants is pretty simple, organic and safe, and means that you make sure you enjoy yourself on a sunny evening. I use the Barbeque coals, crushed to a powder. So basically, have a BBQ, wait until the following day and the coals are cold. Either crush them in the BBQ or tip them into a wheelbarrow, then use a trowel or similar to crush the coals into dust, then sprinkle around the trees and any supporting posts. The coal dust turns the ants black. They struggle to move, can’t climb high without falling off the tree. I reckon it pulls their exoskeletons apart. Within 30 minutes or so, you have an ant-free tree, and to boot a nice fertilser for your tree. Organic, safe and more effective than anything you can buy.