These Permafelt cabbage / brassica collars are made from recycled plastic bottles and protect all brassica plants from cabbage root fly and will repel slugs also.
They are simple, efficient, effective and non chemical. In addition the collars will stop weed germination around the plant and conserve moisture.
They are put on around the stem of the plants at ground level and prevents the adult cabbage root fly from laying eggs near the base of the plants and stops root damage which kills or severelly weakens newly establishing plants. How to use instuctions are on the box and the 18 collars are 10 cm in diameter