Which natural remedy exist against aphids?

[alessandro2011]

The nettle macerate.
A preparation based on propolis: 15 ml of water-alcohol solution of propolis on 5 liter of water.
marseille liquid soap: 20 cc over each liter of water (and mix well).
Strong bitter tea: boil for several minutes, a spoonful of tea in 1 liter of water. Then strain, let cool and use undiluted on the plant and also on the paths of the ants.

Water under pressure over the plant.
Generally is a system used over tree but with caution i think could be used even for small plant.

Good entomophagous insects:
Coccinellidi beetles
Hoverflies the Diptera
Different Rincoti Heteroptera
Neuroptera Crisopidi

adalia bipunctata
aphidius colemani

About chrysoperla carnea they are active against differents things but i don't known if the adult are sufficient good or not, given that they like feed on pollen, nectar and other sugary substances.
In summary i don't known if they can ruin the flowers.
Probably no, but i don't known.
Lotta biologica agli afidi con l'ausilio degli insetti utili

Should always be taken into account the peculiar biological characteristics of util insects.
For example the larvae of Chrysoperla carnea attack aphids immediately once entered in the field and can feed in scarcity of aphids, other prey such as mites and other insects, and respond well to environmental stresses and temperature.

While other type of insects require a lot of prey for work good.
Warning:
As usual when are used good insects and larvae is better don't use other system because even biological system could be dangerous even for good insects.

Later i think i add others solutions.
If someone known other system, suggest it.

[okieOrchid]

I was able to completely eliminate spider mite from my collection using this simple solution : put a couple of drops of Eucalyptic oil into the potting medium.
I repeat this application anout once a month and have NOT seen even 1 mites on any of my 100+ orchids

[sii]

I haven't seen any aphids around here.

But one day i went out to a nursery to check out some 'other' plants. While I was there we watched one of the ladies put ladybugs all over some rose bushes. They are considered a good natural enemy.

Don't know how this translates to orchids, but thought I'd share.