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Managing increasing leek moth in leeks and garlic

Leek moth has slowly been increasing in Eastern Canada preferring to feed on leeks and garlic, but will also feed on onions, shallots, and chives.

In a 2024 leek moth monitoring survey spanning eight locations in six counties in southwestern Ontario, leek moths were detected on sticky cards at all locations during the 2024 growing season. The only exception was two sites in Huron County where no leek moth was detected. In Grey, Oxford, Perth, Prescott-Russell, and Renfrew counties, leek moth was detected on sticky cards.

While there was a peak in leek moth populations during their adult flights, plant damage was only observed on leeks in July at the Perth, Ont. Field site.

Leek moth overwinters and lays its eggs on the meristem of Alliums, eating everything but the roots. Leeks are at the greatest risk to leek moth because the inner portions of the leaves must be marketable, and the crop has to survive all three larval generations of this pest.

With three distinct adult flights per year, the population of leak moth, according to Ontario data, peaks in early-May, early-July, and mid-August.

Travis Cranmer, vegetable crop specialist with the Ontario Ministry of Agriculture, Food, and Agribusiness, writes that insecticides and exclusion nets are effective for managing leek moth.

Cranmer provides further guidelines for monitoring for the pest and managing it with insecticides or – if timed correctly – exclusion nets in his latest post on ONvegetables. | READ MORE

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