Problem with aphids

[Leszek Andrzej Kleczkowski]

We have problem with aphids eating up our Arabidopsis
plants.  Is there some chemical which can be added to
the soil to kill the beasts without affecting the growth
and development of the plants?  We tried spraying the
plants with pyrsol emulsion from Bayer AB, but it works
only temporarily and has also visible effects on plant growth.

Will be grateful for any suggestion

Leszek