Electrophysiological and Behavioral Responses of Theocolax elegans (Westwood) (Hymenoptera: Pteromalidae) to Cereal Grain Volatiles.

Giacinto Salvatore Germinara,Giuseppe Rotundo,Antonio De Cristofaro

doi:10.1155/2016/5460819

Giacinto Salvatore Germinara, Giuseppe Rotundo + Show 1 more

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https://doi.org/10.1155/2016/5460819

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Abstract

Volatiles emitted by the host's food would be the first signals used by parasitoids in the host location process and are thought to play an important role in host habitat location. In this study, the olfactory responses of Theocolax elegans (Westwood), a Pteromalid wasp that parasitizes immature stages of stored-product insect pests developing inside cereal or leguminous grains, to volatiles emitted by healthy wheat grains, their hexane extracts, and different doses of three individual compounds previously identified in cereal grain odors were investigated in Y-tube olfactometer and Petri dish arena behavioral bioassays and electroantennogram recordings. In Y-tube olfactometer bioassays, odors from healthy wheat grains and their hexane extracts were attractive to both sexes of T. elegans. Moreover, hexane extracts elicited arresting effects in Petri dish arena. The three synthetic compounds valeraldehyde, maltol, and vanillin elicited dose-dependent responses in both male and female adult wasps confirming the capability of the peripheral olfactory systems to perceive cereal volatiles. In behavioral bioassays, different doses of vanillin were significantly attractive to both sexes.

Highlights

The use of natural enemies is considered to be an important component of integrated pest management of stored-grain insect pests [1], in storage areas
The olfactory responses of Theocolax elegans (Westwood), a Pteromalid wasp that parasitizes immature stages of stored-product insect pests developing inside cereal or leguminous grains, to volatiles emitted by healthy wheat grains, their hexane extracts, and different doses of three individual compounds previously identified in cereal grain odors were investigated in Y-tube olfactometer and Petri dish arena behavioral bioassays and electroantennogram recordings
Volatile compounds present in hexane extracts of healthy wheat grains were preferred to control hexane in the same apparatus and elicited an arrestant effect in Petri dish arena, suggesting the presence of behaviorally active compounds acting as attractants at long distance and arrestants at short range

Summary

Introduction

The use of natural enemies is considered to be an important component of integrated pest management of stored-grain insect pests [1], in storage areas. Orientation to host plant or host food volatiles in the absence of any host, host damage, and host derived materials have been demonstrated for a number of parasitic wasps [10,11,12,13,14], including some Pteromalidae species parasitizing stored-grain insect pests [15,16,17] These volatiles, generally acting as long distance cues, would be the first signals used by parasitoids in the host location process and are thought to play an important role in host habitat location [18,19,20]. The identification of such synomones has a great practical interest since they could be used as parasitoid behavior modifying compounds to enhance their biological performances

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