I don't have much to add to what you've already been told. I can't
tell if you really meant "fumigation" as in "applying a pesticide in
gaseous form", which is a bad idea, period.

(Claudio Fierro) wrote in message ...
I have two questions about fumigation:
First; is it right to make it in a preemptive way?

No.

And another question about the use of oil based pesticides
against spiders and aphids: Is it safe for our bonsai to use them?

Test first. Trees differ in their sensitivity to oil; the dosage to
use may differ. And read the label: some should not be used above
certain temperatures.

Nina, at a workshop learning to extract DNA from fungi.