A fat, hairy fly resting on daffodil leaves in spring, banded like a small bumble bee, is worth a second look. Narcissus bulb flies lay eggs near the base of the plant, and their maggots hollow out the bulb underground. The damage stays hidden until the leaves come up weak and the bulb turns soft.
Narcissus Bulb Flies: What You See
The adult is the easiest stage to spot, while the larva stays out of sight inside the bulb.
- The adult looks like a small bumble bee, hairy and heavy-bodied, with bands of yellow or orange brown over black.
- It is a small fly, usually seen resting on leaves and other vegetation.
- In California, adults often hover around blooming plants on warm sunny days, feeding on pollen and nectar.
- The maggot inside the bulb is plump, wrinkled and dirty white to yellow, growing from 1/16 inch when newly hatched to ¾ inch when mature.
- A damaged bulb feels soft and spongy, and the inside may be hollowed out or reduced to a brown mass.
- In Washington, a bulb that is not too badly damaged may send up a few grassy-looking leaves.
Adults can show up in Colorado from late April or early May and stay through June.
From the almanac
Bulbs in your state
The dates on this page depend on where you live. Your state's page carries its frost dates, its USDA zones and the year laid out month by month.
Northeast
Southeast
- Alabama
- Arkansas
- Delaware
- Florida
- Georgia
- Kentucky
- Louisiana
- Maryland
- Mississippi
- North Carolina
- South Carolina
- Tennessee
- Virginia
- West Virginia
Midwest
Southwest
West
Pacific Northwest
Canada
Narcissus Bulb Flies or Something Else?
The adult fly is a mimic, so it is easy to mistake for a harmless visitor. A soft bulb has several possible causes too, which is why a single clue is never enough.
Look at the insect and its location together, then cut open a doubtful bulb to settle it.
| Looks like | How to tell them apart |
|---|---|
| A real bumble bee or another helpful fly, hairy and banded yellow and black | The bulb fly is heavy-bodied and often sits on leaves near the base of the plants, and digging there turns up a soft bulb with a maggot at its base. |
| Maggots from other bulb flies, found in daffodil, iris, lily and tulip | The narcissus bulb fly maggot is plump and wrinkled, ½ to ¾ of an inch long, with a short brown or blackish breathing tube at the rear, and it lives in the base of a narcissus bulb. |
| A bulb that rotted for another reason, soft and brown | A leaf-weak clump alone proves nothing, but a plump yellowish white larva inside the soft bulb confirms the fly. |
Bumble bees and other beneficial species deserve to be left alone, so confirm the maggot before you act against anything flying in the bed.
What Causes Narcissus Bulb Flies, and Where It Is Worst
The cause is the adult female. She lays eggs on the leaves near the soil surface or on the crowns, and when the eggs hatch the maggots tunnel into the bulb and feed on the soft tissue. They often burrow in near the basal plate, destroying bulb scales and flower parts.
Timing depends on where you garden. In Washington, the female lays eggs near the bulbs in early summer. In California, eggs go on exposed bulbs or stems at the base of plants in spring or summer. Colorado adults normally emerge in late April or early May and are present through June.
One generation is produced each year. In Colorado, winter is spent as a full-grown larva in a cavity in the base of the bulb. In South Carolina, the larvae overwinter in the bulb and move into the soil in spring to finish their life cycle. The pest can turn up where narcissus grow, so check your local county or provincial extension office for guidance.
How to Treat Narcissus Bulb Flies
No cure brings a hollowed bulb back, so treatment means finding the infested bulbs and removing the maggots before they spread the problem.
- Squeeze suspect bulbs when you dig or handle them, so that soft, spongy ones are separated from firm ones.
- Cut open any soft bulb and look at the base, so that you can confirm a plump larva rather than guess from the rot.
- Discard infested bulbs in the trash instead of the compost pile, so that the maggots cannot finish developing in your yard.
- Leave the leaves on healthy plants until they turn yellow, so that the remaining bulbs keep feeding for next year.
- Replant only firm, clean bulbs, so that you are not putting a maggot back into the ground.
- Ask your county extension office which treatments are approved in your state, so that you use only what is legal and suited to your yard.
Dig carefully, because the bulbs are easy to nick and a damaged bulb invites rot.
How to Prevent Narcissus Bulb Flies Coming Back
Prevention follows the fly’s calendar, so check your local county or provincial extension office for guidance.
- In fall, when you plant new bulbs, check each one and set aside any that feel soft, so that you never bring the pest in with the stock.
- In spring, as adults begin to fly (late April or early May in Colorado), watch the bed on sunny days for the bumble-bee-like fly resting on the leaves.
- In early summer, when females are laying eggs near the bulbs in Washington, keep an eye on the base of the plants where the eggs go.
- After the leaves have turned yellow, tidy the bed and note any clumps that came up with small, weak leaves, because those bulbs are the ones to dig and check.
A clump that has weakened once is a good candidate for a spot check the following year.
Where This Comes From
The details here come from university extension and government pages written for South Carolina, Washington, California and Colorado. Timing and local advice differ from state to state, so check with your own state’s extension service before you act.
Common Questions
How Many Maggots Live in One Bulb?
Usually only one larva develops in each bulb. That single maggot is still enough to hollow it out.
Where Do the Maggots Go in Spring?
In Colorado, the larvae leave the plant in early spring, often exiting through the neck, and pupate in the soil about an inch below the surface. In South Carolina, they also move from the bulb into the soil in spring.
Can an Infested Bulb Recover?
Once infested, bulbs often rot. Some survive but generally produce small, weak leaf blades the following year.