Submitted to: Journal of British Columbia Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/1999
Publication Date: N/A
Citation: Knight, A.L., Croft, B.A., Bloem, K.A. 1999. Effect of mating disruption dispenser placement on trap performance for monitoring codling moth (Lepidoptera:Tortricidae). Journal of British Columbia Entomological Society. 96: 95-102. Interpretive Summary: Sex pheromone-baited sticky traps are an important tool used to monitor orchards treated with dispensers emitting sex pheromone for mating disruption of codling moth. Recent recommendations for both proper trap and dispenser placement have suggested that both traps and dispensers should be placed in the upper canopy of the orchard. Studies were conducted to examine whether the proximity of traps and dispensers influences trap performance. The unexpected results from our first experiment, that traps placed lower caught more moths than higher traps was shown to be due to the presence of year-old dispensers that were still emitting sex pheromone. Following the removal of these dispensers higher traps caught more moths than traps placed lower. In a third test we showed that moth catch is significantly reduced when traps are placed within 0.3 m of dispensers. An evaluation of grower use of traps in mating disrupted orchards revealed that the proportion of traps placed within 0.3 m of dispensers increased from 9.0 to 30.0% from 1996 to 1997 following general recommendations to place traps higher in the canopy.
Technical Abstract: Capture of codling moth, Cydia pomonella L., in lure-baited, wing-style traps placed at varying distances from polyethylene dispensers (Isomate-C+) in the canopy of an apple orchard (mean tree height was 3.99 m) was investigated during 1997. Replicated studies of trap - dispenser position were conducted with releases of sterile moths around each trap. In the first experiment, moth catch was unexpectedly higher in traps placed 1 m below the 1997 dispenser's height (3.38 m) compared with traps at the dispenser's height. No differences were found in moth catch for traps placed adjacent to 1 and 2 m distant from dispensers at the dispenser height. Subsequent analysis of the Isomate-C+ dispensers left in the field from 1996 found that they continued to emit low levels of sex pheromone through July. In the second experiment, the 1996 dispensers were removed from the trees around each trap and moth catch was significantly lower in traps placed 1 m below the 1997 dispenser height and in traps adjacent to the dispenser compared with traps 1 and 2 m distant at the dispenser's height. In a third test, moth catches were significantly reduced when the trap - dispenser distance was less than or equal to 0.3 m for both 1996 and 1997 dispensers. Moth catch did not vary in traps placed 0.3 to 2.0 m from either dispenser type. A post-hoc evaluation of trap placements used in an areawide project situated near Oroville, Washington, in 1996 found that 9% of traps were placed within 0.3 m of dispensers. This percentage of traps inadvertently increased to 30% in 1997 following recommendations that traps should be placed higher in the canopy.