Introduced Pests Outreach Project

Leek Moth

(Click on an image below to see the captioned full-size version)
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6

Scientific Name: Acrolepiopsis assectella
Common Names: Leek moth, onion moth

Known Hosts:
Allium spp. Leek is the preferred host, but other hosts include onion, garlic, chives, and shallot

Key ID Features (Adults, Larvae, Eggs):
Adult is a small pale brown to black moth. Wingspan is about 1/2 inch (12-15mm). The moth is 1/4 inch (5-7mm) long with wings folded at rest. The forewing has a large triangular white marking with small white markings. The hindwings are heavily fringed and are pale grey to light black in color. (Figure 1 and 2)
Adults overwinter in sheltered areas (e.g. buildings, plant debris).
Eggs are white and oval-shaped. Due to their small size (0.4mm) they are difficult to detect.
Larvae are yellowish-green and about 1/2 inch (13-14 mm) long when mature. Each segment has 8 small spots and the head capsule is pale brown. (Figure 3)
The pupal cocoon is 1/2" long. The green pupa is visible through the loosely netted cocoon. Cocoons can be found on the leaves of hosts, neighboring vegetation, and on plant debris. (Figure 4)

Description of damage:
Symptoms include mining and perforations.
When feeding on onion or garlic, larvae spend most of their time feeding inside hollow leaves or stems (Figure 5)
Larvae can bore into onion or garlic bulbs predisposing them to secondary bacterial or fungal infection.
On leek the larvae bore towards the center of the plant to feed on the inner leaves creating a series of pinholes. The larval mining can be seen as longitudinal grooves on mature leaves (Figure 6). This damage renders the crop unmarketable.
Damage is more prevalent near field perimeters.

Similar species or symptoms:
The adult moth is similar in appearance to the carrion-flower moth. See the Ontario Ministry of Agriculture and Food publication on the leek moth for a description and photos.

The cocoon of the leek moth is similar to that of other pest moths such as the diamondback moth.

Fact sheets and references:
USDA, APHIS Pest Response Guidelines

Ontario Ministry of Agriculture and Food- The Leek Moth - An Introduced Pest of Allium in Eastern Ontario

National Agricultural Pest Information System/Cooperative Agricultural Pest Survey

An Integrated Approach to Management of Leek Moth. Agriculture and Agri-Food Canada.

Pesticide Risk Reduction Program, Agriculture and Agri-Food Canada.

Release of a Parasitic Wasp for Biological Control of Leek Moth. Agriculture and Agri-Food Canada.

Cornell University Cooperative Extension Leek Moth Fact Sheet

last reviewed December 18, 2014

Massachusetts Department of Agricultural Resources
The Massachusetts Introduced Pests Outreach Project is maintained by staff at the Massachusetts Dept. of Agricultural Resources. This website was made possible, in part, by a Cooperative Agreement from the United States Department of Agriculture's Animal and Plant Health Inspection Service (USDA APHIS). It may not necessarily express APHIS' views.