General principles of attraction and competitive attraction as revealed by large-cage studies of moths responding to sex pheromone

Abstract

Knowledge of how insects are actually affected by sex pheromones deployed throughout a crop so as to disrupt mating has lacked a mechanistic framework sufficient for guiding optimization of this environmentally friendly pest-control tactic. Major hypotheses are competitive attraction, desensitization, and camouflage. Working with codling moths, Cydia pomonella, in field cages millions of times larger than laboratory test tubes and at substrate concentrations trillions of times less than those typical for enzymes, we nevertheless demonstrate that mating disruption sufficiently parallels enzyme (ligand) -substrate interactions so as to justify adoption of conceptual and analytical tools of biochemical kinetics. By doing so, we prove that commercial dispensers of codling moth pheromone first competitively attract and then deactivate males probably for the remainder of a night. No evidence was found for camouflage. We generated and now validate simple algebraic equations for attraction and competitive attraction that will guide optimization and broaden implementation of behavioral manipulations of pests. This analysis system also offers a unique approach to quantifying animal foraging behaviors and could find applications across the natural and social sciences. Mating disruption of insects is the agricultural practice of dispensing synthetic sex attractant into a crop so as to suppress pest reproduction by interfering with mate finding (1). The Environmental Protection Agency expects this environmentally friendly pest management tactic to effectively supplement the "softer" insecticides as well as to fill critical control gaps left as "harder" insecticides face withdrawal from the marketplace due to tightening governmental regulations (2-4), e. g., azinphos methyl (Guthion) in apple production. There are now more than 100 EPA registrations of insect pheromones for use as pest control agents in agriculture and forestry. Mating disruption for all pests encompasses ≈700,000 ha (5), 160,000 of which target codling moth, Cydia pomonella, the proverbial worm in the apple.Despite 40 years of research and the emergence of a vigorous and expanding worldwide pheromone industry (5, 6), knowledge of how sex pheromones actually interact with target insects as individuals and groups under disruption has lacked a mechanistic framework sufficient for judging whether current practices for implementing mating disruption have been optimized. Here, we introduce and experimentally validate both attraction and competitive-attraction equations as well as a unique analysis system. Their utility in understanding and manipulating animal behaviors might parallel those of the Michaelis-Menten equation and classical enzyme kinetics in biochemistry.Derivation of Equations. Wind traversing a pheromone point source sweeps out an odor plume whose active space and interactions with male moths are schematically represented in Fig. 1. Cumulative catch (C) of male moths (♂) in a trap (T) (Fig. S1 presents pictures of apparatus) baited with a pheromone...

Sex Pheromones and Their Impact on Pest Management

“…If we understood the underlying mechanisms that cause or result in the behavioral modification that leads to disruption of mating, we will be better placed to understand why some applications are successful and others not (Cardé and Minks 1995;Sanders 1996, Miller et al 2010. Attempts to interpret the behavioral response to air permeation treatments should, however, also build on field data on both the behavior of moths and molecules.…”

Mating Behaviors of Cydia pomonella (Lepidoptera: Tortricidae) as Influenced by Sex Pheromone in Electrostatic Powder

“…False plume following to Isomate-Cϩ tubes has been directly observed in the Þeld (Stelinski et al 2004a), and habituation after false plume following has been conÞrmed in ßight tunnel assays . The combination of these two mechanisms as the mode of action of Isomate-Cϩ was recently conÞrmed empirically (Miller et al 2010) and may be the mechanism by which C. pomonella is disrupted by other point-source formulations of pheromone described above.…”

The optimal sex pheromone release rate for trapping the codling mothCydia pomonella(Lepidoptera: Tortricidae) in the field

“…The cultivars were K9 apple (orchard 1); K9 apple, 123 apple, and apple-pear (a common planted pear variety in China which has apple-like shape) (orchard 2); and 5DN pear (orchard 3). The average tree age was [19][20] years in all of the selected orchards, and the plant spacing and row spacing were 3 m and 4 m, respectively. 1-2 spray of beta cypermethrin (1-2 sprays) was applied to each orchard.…”