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Fighting Leek Moths in Garlic Crops Using Trichogramma

Published on: | Created by: Roxanne S. Bernard

Tags: garlic, leek moth, pepper, trichogramma

Field of garlic with small bags of trichogramma to fight leek moth

Leek moth: major garlic pest

Portrait de Roxanne S. BernardTemperatures are gradually rising and the snow is starting to melt. Spring is finally on its way! Garlic bulbs planted in the fall are starting to grow, for harvesting this season. Unfortunately, the milder spring weather brings worry about the emergence of a major garlic pest: the leek moth (Acrolepiopsis assectella).

Leek moth: portrait of a pest

The leek moth is an invasive species, native to Europe. It was spotted for the first time in eastern Ontario in 1993 and in Quebec in 2001. The caterpillars feed on plants from the Alliaceae family (leek, garlic, onions, chives, etc.), causing damage to the young leaves, flowers and cloves, resulting in a loss of yield.

Leek moth: life cycle

  • The adults spend winter in plant debris.
  • Adults become active at 9.5 °C.
  • Females lay 2-6 days after breeding.
  • Females lay 80 to 240 eggs.
  • There are three generations of leek moths in Quebec.

Follow these three steps to protect your garlic from leek moths

1 Scout using pheromone traps

Scouting helps you determine the adults’ period of activity and the size of the populations. This information makes it easier to use trichogramma and apply Bacillus thuringiensis (Bt) at the best time.

Quebec’s Réseau d’avertissement phytosanitaire (phytosanitary notification network) posts informative bulletins that let you know when pests have arrived and when to apply products in your region (sign up at (in French only)..

2 Choose your pest control strategy

Choosing the best pest control strategy will depend on several factors, such as the surface area to cover, your agricultural equipment, your time use, values and more. There are several physical (mini tunnels and anti-insect netting), biological (trichogramma or bioinsecticides) and chemical (pesticides) methods available on the market.

The use of trichogramma as a biological control agent is getting more and more popular in Quebec. Trichogramma cards can be installed without any equipment, at any time of day and in any condition (wind, rain, soggy ground, etc.). They cost about the same as some biopesticides and are safe for the environment and human health.

3 Apply good farming practices

Rotating garlic crops with non-host crops every three years and removing crop residues and weeds will help reduce leek moth populations.

Trichogramma in garlic crops

The trichogramma species used to fight leek moths is Trichogramma brassicae. These tiny trichogramma are less than 1 mm long. As soon as they emerge, bred females actively seek leek moth eggs on the surface of garlic leaves. Once an egg mass is detected, the female lays her eggs inside it (parasitism). The trichogramma larvae feed on the developing leek moth caterpillar, thus eliminating the next generation of leek moths.

Research and deepening knowledge

In Quebec, garlic yields obtained with the use of trichogramma are very encouraging. This method is a good alternative to conventional insecticides and Bacillus thuringiensis-based bioinsecticides (Bt).


It is thanks to the open mind of Quebec garlic growers ( that this solution is now on the market. Some of the growers were looking for an alternative to conventional insecticides, to offer their customers quality garlic grown with respect for the environment and human health.

During the 2017 season, the IRDA* and Université de Laval will be conducting tests to better determine to how trichogramma control leek month populations. Anatis Bioprotection may also be testing different way of setting up the trichogramma cards in the fields at certain growers’ sites, with the aim of ensuring better protection at field edges, which sustain greater pest damage.

See the Tricho-Gard sheet

Informations supplémentaires

  1.   - Leek Moth - A Pest of Allium crops
  2.   - Living with the Leek Moth - An Organic Approach
  3.   - Leek Moth (Acrolepiopsis assectella)

Additional information

  1.   - Leek Moth - A Pest of Allium crops
  2.   - Living with the Leek Moth - An Organic Approach
  3.   - Leek Moth (Acrolepiopsis assectella)

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