On 2/6/04 8:56, in article nDgvc.9$yu2.3@newsfe3-gui, "Sally"
wrote:

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.


I finally remembered to ask my husband about this. He used to grow toms
commercially and was one of the first to use biological controls under such
conditions - just to give you his credentials!
He says that for this year, it may already be too late but the natural
predator is Encarsia. However, given that you have a bad infestation he
thinks it will probably not work this year and that you should use a soap
solution in a spray and see if that works. Next year, get hold of the
predator very early in your planting season. The Gardener usually has
adverts by various biological control companies. This takes time to work
but work it does. It may sound obvious but not everyone thinks of it - so,
it's very important not to use any insecticidal sprays just before or while
using Encarsia. If you can get them this year, you might want to give them
a try but no promises! Ours come from Kopperts which is a commercial firm
but I don't know if they supply to amateur gardeners or have a branch which
does.
I have found this site which has good info and is a supplier, too:
http://www.defenders.co.uk/problems.htm

--
Sacha
www.hillhousenursery.co.uk
South Devon
(remove the weeds after garden to email me)