Carrot Root Fly
As you are growing in raised beds at 18” high the risk of carrot root fly is lower as the carrot flies do not fly much above 50cm (19.5”) but you never know with these pesky flies. If you want to be absolutely sure your crop is protected you could erect an Anti carrot fly screen around your raised bed or alternatively try a Carrot Root Fly Trap. There is also a nematode option that we use at Stephanie’s Kitchen Garden called Grow Your Own Pest Control but this needs to be applied every 6 weeks.
Horticultural Adviser/Kitchen Gardener