The contemporary and prospective risks of resistance to the mating disruption method in moths

Mating-disruption is an environmentally safe pest control method, using synthetic sex pheromone that hampers the ability of males to locate females. The technique is used against many insect pests worldwide, among which moth species are the majority. Recently, reports of reduced efficacy of the method have accumulated. One explanation for its failure is the evolution of resistance to the method. Evidence for resistance to mating-disruption comes from two species of tea pests and the pink bollworm. We describe these examples and discuss possible explanations and modes of action that may have contributed to this phenomenon. In this review, we outline the factors that have the potential to promote resistance to mating disruption (MD). (1) Changes in the pheromone composition that enhance the detection of females by broader sensitivity in males: a) a limited number of components in the pheromone blend allows for a significant change in the ratio of components, followed by a fast male response to the change, or b) a multi-component pheromone allows for an accumulation of small changes in the pheromone over a long time, which enable slow adaptation of males to the changed pheromone. (2) The MD technique applies a partial blend out of the sex pheromone complex. This provides an advantage to sensitive males that are better at detecting the minor components in the blend. (3) Continuous pheromone coverage in space and time, or restricted host-plant species (oligophagous) limits the probability for mate encounters out of the pheromone treated area. Consequently, mating is confined within the boundaries of the pheromone-treated area, with restricted gene flow within a population. The review emphasizes the lack of studies that focus on the effect of the long exposure to an excess of pheromone on the insects’ fitness parameters, the population gene structure, and the subtle or significant changes in the pheromone compositions.