# Induced allopatry as main mechanism explaining trap catch reduction in low dose mating disruption trials on the strawberry pest Acleris comariana (Lepidoptera: Tortricidae)

## TL;DR

This study explores how pheromone-based mating disruption affects the strawberry tortrix pest, finding that males are attracted to dispensers instead of traps, reducing trap catches but not pest numbers.

## Contribution

The study identifies induced allopatry as a novel mechanism explaining reduced trap catches in low-dose mating disruption trials.

## Key findings

- Males are more attracted to pheromone dispensers than to trap lures, leading to aggregation near dispensers.
- High pest density limits the effectiveness of mating disruption due to continued mating encounters.
- Pheromone-based control shows potential but requires optimization for effective pest management.

## Abstract

The strawberry tortrix, Acleris comariana (Lepidoptera: Tortricidae), is a destructive pest of strawberry in Denmark and southern Sweden. The efficacy of pheromone‐based communication disruption of the species was examined in crop fields in southern Sweden. Due to the high cost of purchasing or synthesizing the pheromone (E)‐11,13‐tetradecadienal, lower quantities were applied per ha compared to similar mating disruption studies on other tortricid pests.

When treating 1 ha within fields with 14 or 1.4 g of pheromone and using rubber septa as dispensers, trap catches were reduced by ≥98% versus control areas. When treating whole fields with 0.45–0.90 g/ha and using 1 g SPLAT droplets as dispensers, the effect on trap catch was less pronounced (63–95% reduction vs control fields). A corresponding reduction in larval numbers following the treatment was not achieved. Additional experiments revealed that males are more attracted to SPLAT droplets compared to trap lures, and aggregate near SPLAT droplets, indicating that low catches in traps were due to induced allopatry, a form of competitive disruption. In addition, female‐baited traps were outcompeted when placed close to septum‐baited traps. Pest densities were high, and the lack of control effect could be attributed to high encounter rates between the sexes despite the female competitive disadvantage, making mating disruption less efficient.

Our data show the potential for pheromone‐based control of A. comariana as part of integrated pest management, but the method needs optimization regarding density and strength of dispensers and ways to reduce the initial density of the pest to levels where competitive mechanisms of mating disruption can be efficient. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

This study evaluated pheromone‐based mating disruption of the strawberry pest Acleris comariana (Lepidoptera: Tortricidae). In treated crop areas males were more attracted to the dispensers than to the trap lures and aggregated near such dispensers, explaining the low catches in traps in these areas as an effect of competitive disruption via induced allopatry. With high densities of the pest in the experimental fields, the pheromone treatment was not sufficient to reduce the encounter rates between sexes, and thus the mating frequency and number of offspring larvae in the subsequent generation. Optimization of the method is thus needed for successful mating disruption of A. comariana.