Submitted to: Green Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 7, 2008
Publication Date: December 20, 2008
Citation: Walse, S.S., Alborn, H.T., Teal, P.E. 2008. Environmentally regulated abiotic release of volatile pheromones from the sugar-based oral secretions of caribflies. Green Chemistry. 1(4):205-217. Interpretive Summary: Development of effective pheromone based attractants for Tephritid fly pests is important because the species are quarantine pests and pest outbreaks must be eradicated. Scientists at the Center for Medical, Agricultural and Veterinary Entomology-USDA-ARS have discovered that pheromone components including anastrephin, epianastrephin, produced by males of the Caribbean Fruit Fly, and other pest Tephritids in the genus Anastrepha, are deposited as gamma-hydroxy acid analogues linked to glucose at aggregation sites in oral secretions. When exposed to environmental conditions occurring when flies mate the gamma-hydroxy acid analogues are slowly released from the sugar water matrix in the form of the closed ring lactone pheromones anastrephin, epianastrephin and these attract both males and females to the mating sites. Use of these gamma-hydroxy acid glycosides in attractant lures will allow for slow release of defined ratios and amounts of pheromone components for the purposes of monitoring and control of Tephritid flies for which no effective pheromone based monitoring systems are available.
Technical Abstract: We report a natural abiotic mechanism for the slow-release of volatile insect pheromones from carbohydrate-based solutions. To mark mating sites for future aggregation, male Anastrepha suspensa [Loew] deposit oral secretions (~33 wt. % carbohydrate) containing gamma-hydroxy acid and trans-fused gamma-lactone forms (~2:1) of the diastereomers, epianastrephin and anastrephin. The gamma-hydroxy acids extend emission via equilibrium with the thermodynamically less preferred (~100:1), but more volatile, gamma-lactones. A kinetic model was generated and tested by measuring the effect of several environmental parameters under controlled and ambient inputs, respectively. Results support a gamma-lactone diffusion-limited rate of liquid to air partitioning that varies markedly with relative humidity and temperature. Results suggest that in the field, pheromone emission occurs over several days with a periodicity that complements daily patterns of reproductive activity. This study provides a unique example of connectivity between natural strategies for inter-organism chemical communication and abiotic environmental processes.