Steady on Nick I was also quoting myself when I said "Back to things like
Bordeaux Mixture"

Paris Green and DDT were both in use at the time Bordeaux mix was.

Yes DDT was used from about 1940, and to many 60+ years is a long time ago.
Also The first Organochlorides date back to late 1800's

And I quote...
"....DDT the first of the chlorinated organic insecticides, was originally
prepared in 1873, but it was not until 1939 that Paul Muller of Geigy
Pharmaceutical in Switzerland discovered the effectiveness of DDT as an
insecticide ...."

Probably the answer is a bit of Genetic engineering to make plants resistant
to pests.........
Before any one shouts....... many plants have wild relatives that are
resistant to pests so it could be done without crossing any species
boundaries.......
David Hill
Abacus nurseries
www.abacus-nurseries.co.uk