The grit needs to be at least 1 inch deep. It is not that it is uncomfortable, they need to lay their eggs on the soil so that the newly hatched grubs can move down to where the roots are. If they cannot find the soil then they do not lay their eggs.
They also prefer a peat based compost so another reason to move to non-peat based stuff.
You can use the kind of soil covering sold for the prevention of cabbage root fly infection where you are growing single stem plants. I would still put grit on top of that though.
@GardenerSuze I wasn't logged in properly and the site has given me a weird username. I have been a bit of a stalker for some time and have have dipped in with questions as and when. Vine weevils were the reason I stopped growing lillies in pots. I'll maybe have another go now I know that I can perhaps stop the eggs from being laid. Thank you.
@SonnieB Same happened to me when I joined. If you want to post photos they many be upside down or sideways, don't be concerned, members are use to it!
I have worked as a Gardener for 24 years. My latest garden is a new build garden on heavy clay.
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