Omg yes--the narcissus bulb fly is a nasty culprit and wrecks havoc for me--I used to blame all kinds of things for poor repeat performance in my daffs until I found out (recently) that the larvae of this fly were wrecking my bulbs.
Here's what mine look like:
Typical treatment is to repeatedly spray bug poison around the basal leaves and soil so the larva makes contact with it en route to the bulb and gets sick and dies before it would pupate and emerge as the fly the next year. I've not found an effective chemical to kill only them and not my bee and other friends.
Some folks dig up all their bulbs and hot treat to kill the larvae, replant in fall.
I read something a while back that the 'best' and most effective thing to do --if you have them-- is to kill the females before they can lay eggs. I've learned to recognize the sound they make and last year began practicing my skills at finding and killing them. It's easy enough to squash the writhing pair when they are breeding next to the daffs on the ground...but when they're flying around it's more challenging. They make a very loud high-pitched buzz and they tend to fly straight up when startled so this year I am going to be more earnest about it with a net, but I'm just not home enough...
People also use barriers like Remay to cover the daff foliage so the females can't get to the bulb base. I haven't tried that, but I read they will sleep on the Remay so they are supposedly easy to find and kill in the morning.
