Leek Moth Monitoring Update

Tuesday, April 20, 2021


2020 marked the third season of collaboration between Perennia and Agriculture and Agri Food Canada (AAFC), with support from NSDA in monitored for Leek Moth (Acrolepiopsis assectella) in across Nova Scotia. Leek Moth is an invasive pest native to Europe and was first identified in Canada (near Ottawa) in 1993. Leek Moth has expanded its range in Eastern North America and was first identified in Kings County, Nova Scotia in 2017. It has established itself here and we have confirmed its presence in both Annapolis and Kings Counties in all 3 seasons of the monitoring program (2018 – 2020). If you are a small scale or commercial grower of Allium crops, particularly garlic or leeks, it may be wise to take some time to familiarize yourself with this pest. For more information on leek moth, Cornell and OMAFRA have great resources pertaining to identification, life cycle and management.  

Adult leek moth. Photo: David Fuller, University of Maine Extension.

Larval feeding damage on garlic. Photo: Agriculture and Agri-Food Canada.

Monitoring in 2020 took place at six sites across Annapolis and Kings Counties. Pheromone traps were set out in early April to try and catch the first flight of overwintering adults, which typically occurs when temperatures reach 9.5oC. Throughout the entire season (April – October) trap liners (sticky paper in bottom) were changed weekly and inspected for adult leek moths. Frequent liner/sticky changes allowed us to have a detailed look at flight patterns of the insect at each location. Trap lures were changed monthly.

Pheromone (Delta) traps used for monitoring leek moth. Photo: Agriculture and Agri-Food Canada.

In 2020 we observed up to 3 flights or 2 generations of leek moth in some locations. The first flight of leek moths was caught as early as the end of April at a couple sites and as late as mid-May in others. A second flight of insects was observed at some sites the end of June into early July. There were traps that experienced a third and final flight later in the summer (late July – late August). Interestingly, some locations did not catch any moths until the end of July. Trap data can be seen in the ‘2020 Leek Moth Catches’ graph pictured below.

Leek moth catches observed on a given date for each trap. Each line corresponds to a separate trapping site. 

Overall, data from the pheromone traps are showing similar trends to what has been observed in Ontario. Studies out of Ontario have determined that there are 3 flights or 2 generations of leek moth each season in Eastern Ontario:

    - Overwintering adults emerging in late April to mid-May

    - An early summer flight of 1st generation adults beginning in mid to late June through mid-July

    - A late summer flight of 2nd generation adults beginning in late-July to August.

Focused monitoring continues for the 2021 season and will follow the same trapping procedure as 2020. The goal for this year is to compare the trap data to previous years’ and to validate an insect development model used in other regions.

If you think you are seeing leek moths or feeding damage in your alliums, feel free to reach out to Perennia or check out our Pest Management Guides for Allium crops for products registered for use on leek moths.