Armyworm (Lepidoptera: Noctuidae) in the province of Quebec, Canada: trapping, sex ratios, and female reproductive status

Abstract Outbreaks caused by migrant pests such as the armyworm, Mythimna unipuncta (Haworth, 1809) (Lepidoptera: Noctuidae), are generally unpredictable. In the province of Quebec, Canada, the arrival and dispersal of armyworms is monitored by capturing males using pheromone traps. Because only males are captured in pheromone-baited traps, trap catch is not predictive of subsequent larval occurrence and damage. We used traps baited with a feeding attractant to capture both male and female armyworm moths and evaluate their flight period at 11 sites across the province in 2018 and 2019. The reproductive status of females was also investigated by dissecting their reproductive apparatus to determine if they were sexually active when captured. The results showed two peak flight periods between May and August but high variation at the different sites and between years. Both sexes migrate in Quebec at the same time but in variable and unpredictable proportions. All spring migrant females had mated before capture, whereas some unmated females were captured later in the season. These results provide useful information to better monitor the armyworm in Quebec and to develop more appropriate integrated pest management strategies.