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United States Department of Agriculture

Agricultural Research Service

Title: A Versatile and Quantitative Volatile-Delivery System for Laboratory Bioassays and Example Uses Involving Host-Related Attractants for Carpophilus Humeralis (F.)

Authors
item Bartelt, Robert
item Zilkowski, Bruce

Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 29, 1998
Publication Date: N/A

Interpretive Summary: This paper describes a new laboratory apparatus and technique that scientists can use when studying how chemicals affect insect behavior. Most insects locate feeding sites and mates through their sense of smell, and the chemical signals that insects encounter as they do this can be exceedingly complex. The complexity of feeding-site scents, especially, has required the development of new techniques for studying how these chemicals function. The new apparatus has the ability to regulate, combine, or compare up to four separate volatile sources in any possible way, and to do this quickly and simply. The technique also allows the absolute amounts of chemicals experienced by the insects to be measured rapidly. The volatile sources can be natural or synthetic and simple or complex. The experimental versatility allows important and difficult biological questions to be answered, such as whether a synthetic blend of chemicals is as effective as the natural scent it was designed to simulate or whether a particular component in a blend is really essential for maximum attractiveness. Manipulating insect populations with behavioral chemicals has become a powerful pest management tool, but before the chemicals can be used effectively, it must be understood exactly how they function. Researchers using the new apparatus will be able to address these important questions with greater precision than was possible before.

Technical Abstract: A versatile moving-air system is described for controlling volatile sources for laboratory bioassays. A calibrated adjustable splitter allows any percentage of a given sample air stream to be selected. Four splitters are connected to a single wind tunnel inlet so that up to four different samples can be bioassayed in any desired amount, proportion, or order. Samples can be analyzed qualitatively and quantitatively by solid-phase microextraction (SPME) and GC just before they enter the wind tunnel. System performance was characterized with physical measurements and with bioassay experiments involving the sap beetle Carpophilus humeralis. The system allows rapid chemical and behavioral comparison of ephemeral natural volatile sources and their synthetic counterparts. Fermenting bread dough was used as an example, and the natural and synthetic attractants compared favorably in the wind tunnel at eight dose levels. The system also allows effects of individual components in mixtures to be evaluated at various doses. Using just one sample each for ethanol, acetaldehyde, and ethyl acetate, all 64 possible combinations of the compounds involving four dose levels were tested. Acetaldehyde had a multiplicative effect that was nearly independent of other mixture constituents, but ethanol and ethyl acetate served essentially as substitutes for each other in the bioassay. Responses to all three compounds increased clearly with dose, and behavioral thresholds in the wind tunnel could be estimated.

Last Modified: 9/20/2014
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