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Pheromone release rate determines whether sexual communication of Oriental fruit moth is disrupted competitively vs. non-competitively

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Abstract

Communicational disruption mechanisms for Oriental fruit moth, Grapholita molesta (Busck) (Lepidoptera: Tortricidae), were determined using a suite of mathematical tools and graphical operations that enable differentiation between competitive attraction and non-competitive mechanisms of disruption. Research was conducted in 20 field cages, each covering 12 mature apple trees. Commercial monitoring lures releasing Oriental fruit moth pheromone at a rate of 0.04 μg h−1 and distributed at densities of 0, 1, 2, 4, 8, and 17 per cage were used to evaluate the effect of low-releasing dispensers on the disruption of sexual communication. Graphical analyses revealed that near-female-equivalent pheromone dispensers disrupted Oriental fruit moth competitively. Commercial mating disruption dispensers releasing Oriental fruit moth pheromone at 60 μg h−1 and deployed at 0, 4, 6, 10, 15, 20, and 30 per cage were used to evaluate the effect of high-releasing dispensers on the disruption of sexual communication. Oriental fruit moth disruption shifted to a non-competitive mechanism for high-releasing dispensers. This is the first time such a shift in disruption mechanism has been demonstrated against a background of otherwise identical experimental conditions. Near-female-equivalent pheromone dispensers were also used to quantify the additive effect of an attract-and-remove control strategy compared with competitive mating disruption. We report a five-fold reduction in Oriental fruit moth captures under attract-and-remove compared to mating disruption using near-female-equivalent dispensers. Surprisingly, release of female Oriental fruit moths into these large-cage disruption studies had no measurable impact on male trapping.

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