Diel patterns of emergence and reproductive behaviour in the invasive Swede midge (Diptera: Cecidomyiidae).
Swede midge (Contarinia nasturtii (Kieffer); Diptera: Cecidomyiidae) is a serious invasive pest of Brassica Linnaeus (Brassicaceae) oilseed and vegetable crops in Canada and the United States of America. Pheromone mating disruption is a promising new tactic for managing this difficult pest, but research is needed to determine how pheromone delivery can be optimised. With an understanding of swede midge diel mating patterns, pest managers could limit pheromone release to periods when midges are sexually active. We conducted a series of 24-hour trials to test whether swede midge exhibit diel periodicity of emergence, female calling, and male capture in pheromone traps. We found that females began releasing pheromones almost immediately following emergence within the first five hours after dawn. In the field, we found that males were most active from dawn until late morning, indicating that midges mate primarily during the first five hours of photophase. Low levels of reproductive activity during midday and nighttime hours present opportunities to turn off dispensers and reduce the cost of pheromone inputs in a swede midge mating disruption system.