Notice I didn't say "Aphid Control"? Aphids are a natural part of a natural garden. You have nice pretty plants then you will aphids.
A friend of mine called recently asking for advice for controlling the aphids in his yard and here is a more detailed version of what I told him.
The aphid is a sucking insect and sucks the plants juices, creating stunted or curled leaves and potentially killing the whole plant. They hang out mostly on the stems and tops and bottoms of leaves and reproduce rather quickly. Sometimes you will see ants running around with aphids too. One person asked me if the ants eat the aphids but they actually "farm" them, tending to them for a sweet substance that they excrete. Yum.
There are other beneficial insects used to help control or manage the aphid population such as ladybugs and lacewings. You need a pretty good population of aphids to keep the beneficial insects around and they are usually more effective in a greenhouse environment. Most nurseries though have bags of live ladybugs and kids love helping with them so give it a try, at least it'll be fun.
According to Rodale's Encyclopedia of Organic Gardening, some tips to help prevent aphids in the first place is to plant nasturtiums, to eliminate all weeds and to have humus rich soil . You will hear me say to everyone I meet that the soil is the foundation of the garden. Think you've added enough compost to your soil? Add more. Especially here in Central Oregon where our soil is practically sterile. And if you add top soil to your garden, that is just sterile soil from somewhere else in Central Oregon. If you prepare your planting area well you will avoid much of the problems people have in their gardens and lawns.
Aphids have never caused me much trouble but I also make sure to grow plants that are relatively hardy on their own and don't require much coddling to survive.
For aphids I've always sprayed them off with a gentle yet firm spray from the hose, making sure to get the underside of the leaf too. You probably will need to do this a few times to really eliminate them.
If that is not working then you can try the homemade version of insecticidal soap (you can also buy insecticidal soap too). The soap breaks down the bodies of the aphids, thus killing them.
About.com had a good article in their Organic Gardening section with a recipe for Tomato Leaf Spray. I've never used it but it sounds really interesting. Click here to see their article. The simplest version is to use about 4 ounces (3 tablespoons) of dish soap per gallon of water, spraying this solution on the tops and undersides of the leaves. You may need to spray a few times to get the entire population. As with most sprays, if it's a hot sunny day the water can cause some burn on the leaves so spray earlier or later. This kind of solution, as far as I have read, does not harm beneficial insects.
If you have other questions about gardening or landscaping just leave a comment or send me an email and I'll be happy to help you out. Happy gardening!
Sources: Sciencejrant, Life123, "The Encyclopdedia of Organic Gardening" by Rodale and Staff