Organic gardeners do not use sprays to control pests, instead they get very sneaky and use plants as a deterrent. The best known of these is French Marigolds, Tagetes minuta
which have a very strong and distinctive smell.
We are just about to sow seed in the greenhouse. The plants will be used around brassicas and in the greenhouse around the tomatoes.
This is sometimes called companion planting but it is also older gardening knowledge that has been handed down though generations. It seem to work but we have not done any specific trials.
There is some more information here from the Thompson and Morgan web site.
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