Comparison of Water Pan Traps and Sticky Traps for Monitoring Delia Spp. (Diptera: Anthomyiidae) in Canola

Yellow water pan traps and yellow sticky traps were used to collect Delia spp. flies in plots of canola, var. Tobin, for an entire growing season in the Peace River region of Alberta. At one or more times during the growing season, pan traps and sticky traps captured Delia radicum (L.), Delia floralis (Fallen), Delia planipalpis (Stein), or Delia platura (Meigen). Numbers of males and females caught varied dramatically between the two trap styles, both within and between the various species. Prior to the onset of flowering, cumulative captures of each of the four Delia spp. in pan traps were all significantly lower than on sticky traps for females and males. From the onset of flowering until trapping ended on 17 August, cumulative captures of D. radicum, D. floralis, and D. planipalpis females were similar in pan traps and sticky traps. Sticky traps, however, remained significantly better than pan traps for trapping all Delia spp. males, as well as D. platura females. Pan traps were more suitable than sticky traps for collecting intact specimens for positive identifications. Results indicate that a combination of sticky traps and pan traps should be used over an entire growing season when conducting initial surveys for Delia species in crops such as canola. In routine monitoring programs for Delia spp., sticky traps would be more efficacious early in the growing season and more practical than pan traps. The level of expertise required to accurately identify the Delia spp. complex in canola would be higher for sticky traps than for pan traps.