Narcissus Bulb Fly: Essential Tips and Facts

The Narcissus Bulb Fly is a pest that can cause significant damage to flowering bulbs, particularly those in the Narcissus family. These flies, scientifically known as Merodon equestris, bear a striking resemblance to honey bees or bumble bees due to their hairy yellow or orange-brown bodies 1. Being aware of their appearance and life cycle is essential in order to effectively prevent and manage infestations.

Adult Narcissus Bulb Flies typically emerge from the soil during May, where they mate and lay their eggs near bulbs 2. Once the eggs hatch, the larvae burrow into the bulbs and feed on their insides. This leads to the destruction of bulb scales and flower parts, as well as impeding the growth of healthy leaves and flowers. In some cases, infested bulbs may only produce grassy-looking leaves 3.

Narcissus Bulb Fly Identification

Adults

The adult narcissus bulb fly, scientifically known as Merodon equestris, is a heavy-bodied fly that mimics the appearance of bumble bees ¹. Some key features of adult bulb flies include:

• Sizes ranging from 3/8 to 1/2 inch
• Hairy bodies
• Variable colors from reddish-brown, orange, or tan ²

Larvae

The larvae or maggots of the narcissus bulb fly exhibit the following characteristics:

• Plump and wrinkled bodies
• Grayish-white to yellow color
• Length ranges from 1/16 inch when newly hatched to 3/4 inch when mature ³

Eggs

Narcissus bulb fly eggs can be identified by their presence and location:

• Females typically lay one to three eggs [|4|]
• Eggs are laid on leaves near the soil surface or on the crowns of narcissus plants ⁴

Life Cycle and Biology

Emergence

The Narcissus bulb fly emerges from the soil in May. The adult fly is about 1⁄2″ long and closely resembles a small bumblebee.

Feeding and Development

• Female lays eggs near bulbs in early summer
• Hatching maggots burrow into the bulbs and feed inside
• Larvae are plump, white to yellow, and wrinkled
• Length: 1/16 inch when newly hatched, ¾ inch when mature

The feeding larvae cause significant damage to the bulbs, often leading to bulb destruction. Narcissus (daffodils) bulbs are particularly badly damaged by the Narcissus bulb fly.

Comparison of Bumblebee and Narcissus Bulb Fly:

Pupation and Overwintering

After feeding and development throughout the summer, larvae pupate in the soil to overwinter. The cycle begins again the following May when new adults emerge from the pupae.

Infestation and Damage

Host Plants

The Narcissus Bulb Fly primarily infests bulbs of:

• Narcissus (daffodils)
• Hyacinth
• Iris
• Amaryllis
• Galanthus (snowdrop)
• Hippeastrum
• Nerine

Signs of Infestation

Keep an eye out for:

• Adult flies resembling small bumblebees, about ½” long
• Female flies laying eggs near bulbs in early summer
• Grassy-looking leaves, potentially indicating infested bulbs¹

Impact on Bulbs

Narcissus Bulb Flies have the following impact on bulbs:

• Larvae (maggots) burrow into bulbs near the basal plate
• Feed inside the bulbs, destroying scales and flower parts
• Infested bulbs produce a few, grassy-looking leaves or develop rot²

Prevention and Management

Cultural Practices

• Healthy bulbs: To prevent Narcissus Bulb Fly infestation, start by selecting healthy and disease-free bulbs for planting.
• Planting: Plant bulbs in well-drained soils to discourage the larval growth and avoid overwatering.
• Mowing and cultivating: Regularly mow and cultivate the area around the bulbs to minimize hiding spots for adult flies.

Chemical Control

• Insect netting: Protect your plants with insect netting to keep adult flies away from the bulbs.
• Insecticides: Although many chemical options have been removed from the market, you may still find some available. Consult your local extension service for recommendations that suit your region.

Comparison of methods:

Pros and cons of chemical control:

• Pros
  • Quick results in pest reduction
  • May be necessary in severe infestations
• Cons
  • May harm beneficial insects
  • Potential for development of insect resistance

Remember, a combination of these methods may work best to prevent and manage Narcissus Bulb Fly infestations in your garden. Consult with your local extension service if you need further guidance.

Frequently Misidentified Insects

Narcissus bulb fly, which refers to two species – the large narcissus fly (Merodon equestris) and the small narcissus fly (Eumerus strigatus) – often gets misidentified due to their resemblance to certain bees. They get mistaken for bumble bees, but there are key differences that can help identify them correctly.

Both large and small narcissus flies display yellow or brown markings on their bodies similar to those on bees. However, they belong to the fly family and are classified as dipterans. A comparison of their features can assist in distinguishing them:

Bumble Bees:

• Have two pairs of wings
• Exhibit pollen baskets on their hind legs
• Possess a straight antennae

Large and Small Narcissus Flies:

• Have only one pair of wings
• Lack pollen baskets on their legs
• Possess a distinct L-shaped antennae

Example: A gardener might mistake a large narcissus fly (Merodon equestris) buzzing around their narcissus plants for a bumble bee, owing to the fly’s yellow and black banding on its body.

While the large narcissus fly predominantly damages narcissus bulbs, the smaller species of bulb flies like Eumerus strigatus are associated with several bulb crops, including Allium.

In conclusion, it’s essential to keenly observe the features of the insects around your garden to ensure their accurate identification. Doing so aids in the effective management of pests, thereby protecting your plants from any potential harm.

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