aren't sticky yellow pieces of plastic you poke in the soil here and
there supposed to trap white fly?
How's the ventilation in the greenhouses? Warm enough to open it up
and blow some of them out with fans? Then use sticky yellow traps.
Insecticidal soap sprays? Depends on how bad the infestation and the
damage done so far. Asking in uk.rec.gardening? Someone growing them
under glass there may be more familiar with the problem and what's
available for you to treat the problems. We have a common language
dividing us ;-) We don't call things by the same names! LOL
I have used a wasp called Encarsia formosana, which is a parasite for
white flies and will kill all forms of the pest. These insects won't
remove all the white flies, but then you don't need to remove them
all, just reduce the population. I'm not sure of the name of the
company from which I bought them, something like Biological Controls,
but you can do a google search and easily find sources.
These come on a little card. You attach these to the plants, after
uncovering and the wasps then fly around and attack the white flies.
This is beautiful - they do all the work and there are no side effect.
These wasps don't attack anything but white flies.
The downside is they are rather expensive. However, I've not found any
chemical which controls sufficiently. I have had decent luck with Neem
oil, you might try that as a cheaper alternative. If you use Neem oil,
be sure to spray the undersides of the leaves.
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
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,
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