This is a cross post from The Cottage Garden Forum. I am hoping to get some good advice here.
Here is a link that might be useful: Ants Help
Contrary to popular myth ants are not really a problem. If in your barrel planter they pose, to you, a problem a simple way to get rid of them is to replace the soil. If replacing the soil is not an option then you could saturate the soil that is there now with water and that should drive the ants out.
In some instances, ants are a real problem....hardly one of the imagination, as Kimmsr intimates.
In containers, they can leave roots high and dry. Depending upon the ant species, they can feed on fruits or veggies you may be growing. They may also prevent efficient pest control, too, if they are actively protecting a scale, mealybug, or aphid population with their bites or stings.
So, you decide if these ants pose a problem to you or just a bit of a nuisance. In my part of the country, a swarm of ants almost always means fire ants. Not only do they bite and sting, but can do considerable real (not imaginary) damage to plants.
In other parts of the country, if ants have literally taken up housekeeping in your container, you'll need to do something about it.
This is about the only time I recommend Diatomaceous Earth (DE). You can find food/horticultural grade DE in almost any garden supply outlet. It can be sprinkled on the top of the soil and it will eventually work itself into throughout the container. I've even seen ants carry DE into their nests! DE's razor sharp edges abrade the exoskeleton of the ants ( and all other insects, so don't use in the garden), causing dessication and eventual death.
Don't use the DE that is manufactured for use in pool filters.
"DE's razor sharp edges abrade the exoskeleton of the ants (AND ALL OTHER INSECTS, so don't use in the garden), causing dessication and eventual death."
That isn't true. DE only kills insects that have an exoskeleton or carapace, whether they are good or bad. It doesn't harm bees, it doesn't harm earthworms, etc.
Prior to a year ago or so, the info on DE was pretty accurate. Then some bozos got hold of it like they do those e-hoaxes, and now there are sites all over that list the horrors of DE.
Thinking that maybe some new info had cropped up, I googled 'diatomaceous earth bees' and looked at page after page and couldn't find any info from any scientific source that indicated bees were suddenly at risk from DE. All the 'info' was from a couple of commercial sites that were selling insecticides and those 'anyone can put info here' question/answer sites. Look for yourself, and you'll see.
So don't panic, folks, it's just the e-hoaxers and nothing-if-not-all obsessive-compulsives at it again.
Many people have been taught all their lives that ants are a problem and so they firmly believe that. Ants are part of Ma Natures recycling machine, helping clean up our planet after us, removing stuff we throw away. Ants are more beneficial then they are a problem, although sometimes where they are can be problematic.
There is no real need to do anything to kill those ants off even if where they are is a problem, simple create conditions they do not like so they move. Spread Diamotaceous Earth around can get to be a very expensive means of control, and more often then not is really ineffective.
You are misinformed, Sue. DE should never be used indiscriminately in the outdoor environment where it can come into contact with a wide range of insects and other non-target organisms. Insects, by the way, come fully equipped with an exoskeleton. I cannot think of a single example of one that doesn't. Please educate us if you know of such a creature.
To use DE responsibly, do not broadcast the product widely and certainly not over flowers. My suggestion that it be a good solution to an ant problem in a planter is a good one.