brassica rootfly collars?

Never had to do it myself, but I know in the past others on here have made them from roofing felt, cardboard, carpet underlay, hanging basket liners............ get the pattern?

I was given a great tip by Clive Bevan the Giant Veg Expert, and touch wood, I have never had a problem

He advised me that a short stick of Rhubarb planted in the whole before the Brassica, was a good cure for root fly and anything else which attacked the plant from beneath

Just make the whole, drop in the rhubarb and plant on top

It is something in the Rhubarb which all species hate. Apparently, humans are the only living creature who like rhubarb

He also advised to cook it up and drain the fluid. Let it cool down and then use it as a spray against white and black fly. I have to say, it does work and it's organic

I had a bad attack of root fly last year, although I used felt collars. They did not make any difference. It's easy to tell which plants are affected as they are smaller than the others. I pulled them up, searched for and destroyed the culprits, including the pupae, and put in new plants.
This year I intend to use old pairs of tights over the plants, down to the soil, in the hopes that it will keep them off and stretch with the plants. Haven't tried it before so I don't know if it will work or not.