You can buy Derris from any nursery / garden centre or organic catalogue/or online in Uk unlike in France where you cant get it anywhere - it works a treat but isnt cheap - any suggestions for alternatives. I have tried companion planting with marigolds to some effect. This is the second batch of flea beetles this summer and they are playing havoc with my good growing cabbages, and caulis. if anyone knows a supplier in France please pass on any info you have.