A new report of leek moth has been confirmed this summer in Coos County, by our state entomologist, Piera Siegert. This confirmation included adult moth activity in pheromone-baited traps, as well as larvae and pupae in onions and leeks. Leek moth has now been found in several gardens and farms in Grafton and Coos Counties. While this invasive species has not be found in southern regions, NH's Division of Plant Industry continues to monitor vegetable farms for adult moth activity in Plainfield, Cornish, Charlestown, Keene, Hollis, New Boston, Peterborough, Milford, and Litchfield. Please let us know if you have damage that you believe is caused by leek moth.
Leek moth (Acrolepiopsis assectella) arrived in Vermont in 2012 and was first reported in New Hampshire in 2016. While this new report does not expand the known geographic distribution of this pest insect, we are particularly interested in tracking any potential spread.
The caterpillar of this moth feeds on Alliums, including garlic, onions, and leeks. There are three generations of this pest, and it is active starting in very early spring (once the soil temperatures hit 50F) in cycles through mid-late August. As you pull your garlic, pay attention for signs of the damage. The damage can be confused with that caused by thrips, botrytis blight, and saltmarsh caterpillar – but it is distinct and the caterpillar is easy to identify. There are some excellent photos of the damage in these three publications:
- Leek Moth Identification and Management Guide, Cornell University
- Leek Moth – A Pest of Onion Crops. Ontario Ministry of Agriculture, Food & Rural Affairs
- Leek Moth, Massachusetts Introduced Pest Outreach Project
These publications also detail management tactics. In addition to chemical approaches, rowcovers and other methods of exclusion can be effective.
