Same answer I Posted at your question at the IPM Forum.
Aphids are generally more likely to infest plants with lush green growth, plants growing in soils with too much available Nitrogen although they can be found on other plants. Aphids also produce live young, and start doing that almost as soon as the are born so by the time you see an Aphid you probably have several generations already present.
The simplest means of control is to knock the wee buggers off the plants with a sharp spray of water. Now many people that know not whereof they speak will tell you that those Aphids you just knocked off will simply return, but these wee buggers are so dumb they know not whereof they came and die before they figure out where they need to go. What you will see is the next generations moving into the vacancy you created, so it takes some time and repeat applications of the water spray, as well as digging into your soil to determine why your plants might be so attrractive to these pests.

Introduce some green lacewing larva to you aphids. Be prepared to say goodbye to your aphids. Easy, quick and natural..;-)

Thanks for replying to both of my posts. Sorry I double posted (annoying, I know).

I have been battling these green buggers with water, and a paraffin spray on occasion...

Is there anything I can do between taking my peas out and putting my tomatoes in to prevent the cycle from continuing on my tomatoes?

bigdaddyj~I used ladybugs last year when our plum tree was badly infested... Maybe I'll give the lacewings a try if the aphids stick around.

Sorry. But there's at least one kind of aphid for every kind of plant. And numerous kinds for every season. They are part of having a garden.

There are people thoroughly convinced that insect pests are just a part of gardening and you must spray a lot of poisons around, poisons that also kill off beneficial and predatory insects, to control them. There has been a lot of research done and there are more gardening articles being written that tell you that getting your soil into a good healthy condition so you can grow strong and healthy plants will lessen the likelyhood of having and needing to control insect pests.
Paul Zimmerman, in an article that appears in the current issue of Fine Gardening magazine tells you just what I have been telling people for years. Grow your plants in a good, healthy soil and the plants will be strong and healthy and be better able to ward off and withstand insect pests and plant diseases.

You are so right, kimmsr. However, insect pests and plant diseases are a part of the normal scheme of things, too. Good, healthy soil, and strong and healthy plants can tolerate a balanced population of the problem organisms. Those conditions do nothing prevent pests and pathogens from arriving.

What you have been repeating over and over is tried and true. Nothing new, but certainly worth repeating. It is also important to know that a healthy garden will have aphids, will have mites and caterpillars and will have billions of spores of pathogens.

Learning to accept and manage the problems is all part of 'culture'. It's good for gardeners like momma to know that, and to learn about some of the many methods of control they have to choose from. Momma has done a good thing in switching fertilizers, perhaps. She might also try to be even more watchful, especially when the crops are young, so that she can do some hand removal before those 'green buggers' get the upper hand.

Which they will do, no matter how 'good, healthy, and strong' everything may be. A healthy tomato plant doesn't repel aphids....the plant is just able to withstand the onslaught longer.

I agree good soil is a good starting point because your plants are in peak condition and can ward off attacks of either disease or insects better than those grown in mediocre soil. But it's only a start. BALANCE is key after that. Aphids and whiteflies starting to take control, perhaps due to weather or biological cycle, which is completely natural, well you can help nature out. Find a natural solution. Green lacewings will put things back in balance again and they are better killers than ladybugs who tend to fly away. You can kill every aphid in your garden with Sevin but you'll next be attacked by spidermites, it's proven. Use of chems is a never ending cycle...control this and you cause this other thing. BALANCE is key and sometimes we need to adjust the weights a bit...;-)

A tomato, or any other plant, growing in a good healthy soil not only will have fewer Aphids, but as some research has shown can repel them as well. No one has ever written that growing plants in a good, healthy soil will guarantee a pest or disease free plant, although that is apparently what some peolle have read into what was written. But much research has been done and has confirmed that plants growing in a good, healthy soil are better able to ward off insect pests and plant disease better then plants growing in not healthy soils.
Many people are told that all they need to do to garden is go and buy some "fertilizers" and dump them on the soil, but that simply provides plants with an excess of certain nutrients, not a balanced diet, which makes those plants more susceptible to, more attractive to, insect pests and plant diseases. That is why I try to tell people how to get their soil into a good, healthy condition.

Well said, bigdaddy!

Kimmsr, I don't believe that you try to tell people HOW to do anything. You make statements but without helpful instructions. Perhaps if you tried to offer some helpful suggestions. Give some examples of what you do in your own garden; what has been successful and what has not.