I have a persistent problem with red spider in the greenhouse. I know
that people do use biological controls successfully (Sacha's husband has
for years and was one of the pioneers), and I've had success with the
red spider predator in previous years.

However, in my but of W Yorkshire, we have had three rotten summers on
the trot. The last two years the red spider predator seemed to have no
effect, and I came to the conclusion it wasn't very happy unless the
weather was warm.

This year, the early part of summer was shaping up a bit better, so I
bought the predator. And then the weather went downhill and once again
the predator seemed to fail. I gave it about 6 weeks (when successful,
there has been about 3 weeks of apparently no effect, then after that
I've suddenly realised there don't seem to be any red spider around any
more) and since then I've operated on a combination of spraying with
soapy solution rather than water and removing the worst affected leaves,
and this has kept it to a level where the plants have been cropping
reasonably well.

Has anyone else noticed this? Is it a known problem that biological
controls work better in the warm south of the country? Or am I imagining
it?


--
Kay