I really sympathise with you having suffered this problem!
We have 2 20’x 60′ polytunnels that were no dig, converted from pasture with a huge residual wireworm population (click beetle larvae) – we took away their food source – grass roots – so they had no choice but to eat our crops. They particularly seem to enjoy tunnelling up into the stem/neck of lettuce, took about half of our french bean plants and lettuce, I have found up to 12 on a single plant. We are growing on a small commercial scale so it’s quite challenging!
I removed every affected plant, checking the root zone carefully, as there was rarely just one wireworm, tried burying cut up potatoes stuck with wire and coloured piece of baler twine to mark them, but these need to be checked regularly and ’emptied’-limited success. I have read you can use the nematodes used for chafer grubs – but they are not specifically for wireworm and are expensive. There’s also a biodynamic approach – collect them, burn them and collect the ash which is diluted and watered onto the affected area, I may still try this!
I hate to admit we have now dug the tunnels and removed loads by hand – cultivation is generally recommended – then we let the chickens in the worst tunnel over last winter.
On a brighter note they didn’t really bother the tomatoes, which were in 9cm pots when planted out last year. I also grow extra plants and keep replacing those they damage.
Hope this helps?(!)
Good luck – the first 2 years are meant to be the worst…
Regards,
beansy