"Sally" wrote in message ...
Despite my using companion planting, my greenhouse tomatoes are becoming
infested with whitefly. Any recommendations of biological control would be
gratefully received.
Thanks so much

The ONLY remedy you need to reduce population to virtually 0 is
to feed tomatoes with a 5% water solution of rotted kelp (as in seaweed).
If you can't get it free from the ocean, buy it in the garden store
as a concentrated solution. Feed them by watering with that solution
occasionally, as required. I do it once a week, starting from seedlings
stage.
If you rot the kelp (in a closed container) yourself, make sure to
wash the sea salt off first. To rot kelp, just stuff it into a barrel,
close the lid and wait 2-3 weeks (depending on temperature). Stinks,
but works.
Good luck.