I have lots of aphids every spring, do little or nothing about it, and find that they are controlled by predators by mid-June each year. This is a common experience, so it could just be coincidence that you have tomatoes nearby.

No, probably not. Aphid population is a function of weather and predator populations. Spring is their boom time, and predators lag the aphid population--when the number of predators increase as the season goes on, the aphids decrease.

Easy and safe control for aphids is to wash them off the plant with the hose every day for a few days.

Just to add to the case for the cyclic nature of aphid infestations: "Aphids tend to abandon rose bushes when the sepals of the blossoms open. This is perhaps related to observed increases in catechin in the rose tissue during the same period of time" (I took this note from some journal abstract, don't have the original reference). Catechins are phenolic compounds with a bitter taste and increased concentrations in rose tissue have been correlated with aphid feeding activity.

Mike
Your explanations are most informative.
I'm always interested in the Hows and Whys of nature.

I have an infestation of aphids right now, coinciding with a lot of new growth and buds on my roses. The weather has also turned very hot and humid - does that have anything to do with it? Anyway,I've been squishing and hosing them off every day. But this morning I noticed that the troops have finally arrived! They will surely be the best-fed in town!
Sir Thomas Lipton buds (sorry, a bit blurry)
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Ladybug larvae to the rescue (there were many more...)
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We just have to be patient, and nature usually comes to the rescue.
Judith

Judith,
What's so great about your photos of Lady Beetle instars (the part of the life cycle before they are the Lady Beetles that we recognize more often.) is that those are the first instars and you can expect two molts before they reach 'beetle-hood'. And the instars eat a lot more aphids than the beetles do.
Ann

Darn! I thought I had discovered something that would be written up in garden books and make me famous!

Thanks, Ann, didn't know that was the proper name (instars).They can eat all they want, there's plenty to go around! Of course, I don't know what those buds will look like when they open up. They're up so high I can't reach them with the hose without spraying the people next door!(they might not mind though, with all this heat and humidity we're having:)
Judith