Well, I thought growing garlic would be foolproof. It is easy to grow garlic! What would want to eat it? Well, here is one of those garlic growing problems I didn’t anticipate- the leek moth.

At our orchestra party last week, a gardener friend and I got to talking around the kitchen counter while munching on post-concert treats. My mom was also there, and I am pretty proud of the gardening skills I’ve been researching and practicing. So, I was telling both of them about my garlic and about how I’ve made a row cover for my brassicas.

He asked the game-changing question: Do you use row cover on your garlic?

WHAT??? Row cover on my garlic. Why EVER would I need to do that?

That’s when he told me that the Haliburton Garlic Growers association is now involved in a research project to find out more about the leek moths in question.

I told him I didn’t think I had any since my garlic seems to healthy. BOY, was I wrong. lol. The next morning when I went out to check my garlic, low and behold, I found that many plants had this lovely garlic pest. Luckily, I don’t think my infestation was too bad YET, so I’ve been picking and squishing.

Check out the OMAFRA (Ontario Ministry of Agriculture, Food and Rural Affairs) website here for information about the leek moth life cycle and control.

I will summarize some of the main points of the OMAFRA article that were particularly important to my research:

  • adults moths emerge and become active when temperatures read 9.5 degrees Celsius (they don’t lay eggs yet, just become active)
  • eggs are laid one at a time. This is a good thing! The eggs are laid on the lower leaf surfaces when night temperatures are above 10-12 degrees celsius
  • females lay up to 100 eggs over a 3-4 week period
  • after several weeks of active feeding, larvae (caterpillars) move onto foliage and spin cocoons. (EASY TO SEE- get them before they can hatch!)

Why not get them now at this tiny caterpillar stage? If you miss this stage, get them when they move out onto the leaves to make their cocoons. Then they can’t become new moths which will then lay new eggs, and so on, and so on.

But it still bothers me to squish them…they are living things that are just going about their natural way of life. I would much rather prevent them from growing on my garlic crop. If we can prevent the moths from landing on the garlic in the first place, they will have to find a wild allium (leek) instead. They will fly into the woods and set-up shop there instead of on the leeks. Next year, I am definitely going to use row cover to prevent them!

  • Pupation (time to metamorphosis in the cocoon) is around 12 days. That means that you have 12 days to find them before they hatch into moths.
  • the moths have 3 “flights” or moth generations. The first one is when the weather warms up and the first moths get to work-late April to mid-May
  • The first generation of new moths are from mid-to-late June until mid-July
  • The second generation of moths is from late-July to mid-August.

All of these dates will be dependent on when those first moths emerge and lay their first eggs.


If you can get the row cover on before dusk when you think the moths will be trying to lay eggs, you should be able to curb the caterpillars, which will them eliminate/stunt the 1st and 2nd generations from being born!

Encourage predator insect species. You can find out all about these on the OMAFRA website.

These leek moths have not made their way everywhere. Hopefully, you don’t have them where you live and if you do, please leave comments to start a conversation on what you have done to control or prevent them from ruining or stunting your garlic crop.

Have a leek-moth-caterpillar-free day!