Turnips being tunneled by grubs

Hi. I *think* what you have is cabbage root fly maggots. Turnips are actually brassicas and therefore suffer from the same pests as cabbages, broccoli, etc. Cover your turnips next year as you would other brassicas. You can buy nematodes to water on your crops too which are supposed to get rid of them, but not getting them in the first place is probably better!

I got Cabbage root fly last year on my cabbages and had to dig them up wash the roots and replant them elsewhere and they did still produce a crop. Interestingly the turnips weren't affected. This year I had no other spring or summer brassicas and so my turnips have been tunnelled! They too will be under the mesh next year!