Hi Markyb
My very first crop of potatoes was attacked by wireworm - same kind of sitaution as yours; newly cleared couch grass. Not much damage - but enough to set me to find out about wireworm.
The grass was ideal habitat for the little sods - a real happy home for them. They bred like ...... well, like only beetles can.
In your plot, last year, they laid their eggs; these will hatch hungry grubs in the spring - and find nothing to eat, except your potatoes!
The good news, is that once they metamorphose into beetles, they promptly fly off to a much more "friendly" grass patch near by - and lay their eggs there!
The problem rapidly diminishes in following years.
Things you can do to reduce the problem this next year
- When you first clear your bed, move the grass turves off the bed (and so most of "your" eggs), and put them on the compost heap. This alone will substantially reduce your population.
- Grow potatoes which can be harvested before September in the year after clearing the bed; apparently you will avoid the main damage season.
- And I've read about making traps - burying slices of potato (attached to skewers) in the bed; check the slice regularly, and replace when the wireworms tunnel in.
Good luck - Gavin
