I've been looking at this as my turnips did nothing this year. The pest is associated commercially with oil seed rape growing (so don't buy stuff containing this could be a start). So if a lot is grown in your area you could be struggling.
Life cycle is here; https://ahdb.org.uk/knowledge-library/ca...lea-beetle
Some sites recommend companion planting with rosemary and thyme. I know Rorbert Milne recommends thyme (20cm+ across plants at 1 per sq.m.) for cabbage root fly in all brassicas. He recons it is 90% effective. So I would try, grow as long as possible undercover with a thyme plant and, when planting out, plant out the thyme as well. You could try covering with fleece as well. As they are very small, environmesh coul let some through may be.
Robert also says that most years they are not a serious problem and that keeping the ground damp is fairly effective (may be pak choi would be different because of when it is grown in the beetles life-cycle).
Life cycle is here; https://ahdb.org.uk/knowledge-library/ca...lea-beetle
Some sites recommend companion planting with rosemary and thyme. I know Rorbert Milne recommends thyme (20cm+ across plants at 1 per sq.m.) for cabbage root fly in all brassicas. He recons it is 90% effective. So I would try, grow as long as possible undercover with a thyme plant and, when planting out, plant out the thyme as well. You could try covering with fleece as well. As they are very small, environmesh coul let some through may be.
Robert also says that most years they are not a serious problem and that keeping the ground damp is fairly effective (may be pak choi would be different because of when it is grown in the beetles life-cycle).
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