Narcissus Bulb Fly
Merodon equestris
A bee-mimicking hover fly whose single fat maggot eats out the center of a daffodil or other bulb, so the bulb rots or sends up only weak grassy leaves with no flower. It is the most damaging pest of daffodils and also attacks other amaryllis-family bulbs such as amaryllis, snowdrop, and nerine.
🔎 How to spot it
The adult looks like a small bumblebee, about half an inch long and covered in yellow, orange, or buff hairs, and it hovers and basks near the planting in late spring. The larva is a single plump, wrinkled, dirty-white maggot up to about three quarters of an inch long, found curled in the hollowed-out heart of the bulb. A soft bulb with a rotten, maggot-filled center is the diagnostic sign.
🥀 Damage it causes
The female lays eggs near the necks of the bulbs and on the soil as the foliage dies down, and the maggot burrows in through the basal plate and eats out the inside of the bulb. A hollowed bulb usually rots, fails to sprout, or produces only thin, grassy leaves and no bloom, and a single maggot can destroy a bulb. Damage shows up the following spring as blind, leafy-only or missing plants.
🛡️ Prevent it
Because females are drawn to the holes left in the soil as foliage dies, firm or lightly cultivate the soil over the dying leaves and consider deeper planting, around six inches or more, to make it harder for maggots to reach the bulbs. Bulbs grown in shadier, cooler spots are attacked less than those in warm, open sun the flies prefer. Lift and inspect bulbs and discard any that feel soft, and buy firm, sound bulbs from a clean source.
🧯 If it is already here
There is no home spray that reaches the maggot inside the bulb, so control is cultural: dig up and destroy soft, infested bulbs to remove the larvae before they mature. Knocking down the soil and folding over the dying foliage to close the entry holes deters egg-laying, and covering valued clumps with fine mesh during the adult flight in late spring keeps the flies off. Commercial growers use hot-water treatment of dormant bulbs.
💡 Good to know
The narcissus bulb fly is the usual reason a daffodil clump comes up all leaves and no flowers, with one or more soft, hollow bulbs to confirm it. Since each bulb is destroyed by just one maggot and there is no rescue spray, prevention and rogueing out infested bulbs are the whole of control. Deep planting and disturbing the soil over fading foliage are the simplest defenses for a home garden.
🌱 Plants it attacks
2 plants in the library can be attacked by this pest
For educational and informational purposes only. Pest control advice is general guidance drawn from university cooperative extension sources; always identify a pest positively and read and follow the label on any product before use, especially around food crops, children, and pets.