**Narcissus Bulb Flies** (*Merodon equestris*) are hoverflies whose larvae (maggots) are a severe, destructive pest of ornamental bulbs, particularly **Narcissus** (Daffodils), as well as amaryllis, hyacinths, and tulips. The conflict is the death or severe weakening of the bulb: the female fly lays eggs near the plant, and the larva bores into the bulb, consumes the internal tissue (often the central growing point), and causes the bulb to rot and fail to flower or grow.
Taxonomy and Classification
Narcissus Bulb Flies belong to the order Diptera (flies). They undergo complete metamorphosis. The adult flies are beneficial pollinators and harmless, often mimicking bumblebees in appearance. However, the larval stage is highly destructive, spending nearly a year inside the bulb feeding and developing.
Physical Description
Adult flies are 1/2 inch long.
- **Adult Fly (Key ID):** Large, fuzzy, brown/yellow/black flies that look remarkably like bumblebees (Batesian mimicry).
- **Larva (Key ID):** A single, large, grayish-yellow, legless maggot, up to 3/4 inch long, often found near the core of the rotting bulb.
- **Damage Sign (Key ID):**
- **Soft Bulbs:** Infested bulbs feel soft and spongy when squeezed.
- **Foliage Failure:** Infested plants may produce stunted, distorted, or yellowed foliage, or fail to emerge altogether.
- **Entry:** Small hole often visible near the neck of the bulb.
- **Conflict:** Destruction of ornamental bulbs.
Distribution and Habitat
Narcissus Bulb Flies are found in Europe, North America, and other areas where ornamental bulbs are grown. Their habitat is the soil surrounding bulb beds and the internal tissue of the bulbs themselves.
Behavior and Conflict
The conflict is the total loss of the bulb.
- **Central Damage:** The larva typically moves to the base plate of the bulb and consumes the growing point, ensuring the bulb cannot produce foliage or flowers.
- **Overwintering:** The maggot overwinters inside the bulb, making it difficult to detect the infestation until the following spring when the plant fails to emerge.
- **Entry:** Adults are attracted to the foliage of the plants in spring and lay eggs near the base of the plant once the leaves begin to yellow.
Management and Prevention
Control is based on inspection, sanitation, and physical protection.
- **Discard:** When planting or storing bulbs, carefully inspect them and immediately discard any that are soft, spongy, or show signs of maggot entry.
- **Deep Planting:** Planting bulbs at least 8 inches deep can deter the fly from reaching the bulb neck to lay eggs.
- **Sanitation:** Remove all dying foliage and loose soil from the bulb area immediately after flowering to eliminate egg-laying sites.
- Drenching the soil around the bulbs with a residual insecticide may offer some protection, but this is often considered too disruptive in the home garden.
Conservation and Research
Narcissus Bulb Flies are managed as ornamental pests. Research focuses on developing hot water treatment protocols that can kill the larvae inside the bulb without damaging the plant tissue, particularly for commercial nursery stock.