In article , Rosie wrote:
Why does this work?

I sprayed some water from my washing-up onto my roses and instead of being
covered in greenfly they are now covered in black(dead)greenfly.

How does that work then?

There are two mechanisms. One is that it washes off their waxy coat
that protects them from dehydration, and the other is that it clogs
the pores through which they breathe. I believe that it is primarily
the former, but I could be wrong.

For this reason, pretty well any soap-like liquid will work.


Regards,
Nick Maclaren.