Efficacy of Isomate-CM/LR for management of leafrollers by mating disruption in organic apple orchards of western Canada

Results of a three-year study demonstrated that Isomate-CM/LR, a polyethylene, single tube-type pheromone dispenser releasing an incomplete mixture of several species' multi-component pheromones is an effective management tool that provides multiplespecies mating disruption for Choristoneura rosaceana (Harris) and Pandemis limitata (Robinson). When applied at a rate of 500 dispensers / ha within the orchard and the equivalent of 2000 dispensers / ha to trees on the orchard perimeter, levels of control were adequate for production of organic apples in British Columbia, Canada. Trap catches with synthetic pheromone lures were reduced by 79-99% and mating of females on mating tables was reduced by 87-98% in these species. At harvest, damage from leafrollers in pheromone-treated organic orchards was below organically-acceptable economic levels (5%) and similar to damage levels observed in insecticide-treated conventional orchards (2%). Over three years, total trap catches of these two leafrollers and their damage decreased in four of five orchards treated with pheromone, but catches and damage from leafrollers increased in one orchard. These indices remained relatively unchanged in paired insecticide-treated conventional orchards over the same three-year period. In pheromone-treated orchards, levels of damage from leafrollers at harvest were positively correlated with total leafroller catches in pheromone monitoring traps. Use of Isomate-CM/LR as a supplemental pest management tactic in organic orchards will help to reduce damage and economic losses from leafrollers that have been increasing under the area-wide codling moth sterile insect programme ongoing in this semi-desert, montane apple production region