Sex Pheromone of the Alfalfa Plant Bug, Adelphocoris lineolatus: Pheromone Composition and Antagonistic Effect of 1-Hexanol (Hemiptera: Miridae)

Sándor Koczor,John C Caulfield,Michael A Birkett,Éva Bálintné Csonka,John A Pickett,Miklós Tóth,David M Withall,József Vuts,André Sarria

doi:10.1007/s10886-021-01273-y

Abstract

The sex pheromone composition of alfalfa plant bugs, Adelphocoris lineolatus (Goeze), from Central Europe was investigated to test the hypothesis that insect species across a wide geographical area can vary in pheromone composition. Potential interactions between the pheromone and a known attractant, (E)-cinnamaldehyde, were also assessed. Coupled gas chromatography-electroantennography (GC-EAG) using male antennae and volatile extracts collected from females, previously shown to attract males in field experiments, revealed the presence of three physiologically active compounds. These were identified by coupled GC/mass spectrometry (GC/MS) and peak enhancement as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal. A ternary blend of these compounds in a 5.4:9.0:1.0 ratio attracted male A. lineolatus in field trials in Hungary. Omission of either (E)-2-hexenyl-butyrate or (E)-4-oxo-2-hexenal from the ternary blend or substitution of (E)-4-oxo-2-hexenal by (E)-2-hexenal resulted in loss of activity. These results indicate that this Central European population is similar in pheromone composition to that previously reported for an East Asian population. Interestingly, another EAG-active compound, 1-hexanol, was also present in female extract. When 1-hexanol was tested in combination with the ternary pheromone blend, male catches were reduced. This compound showed a dose-response effect with small doses showing a strong behavioral effect, suggesting that 1-hexanol may act as a sex pheromone antagonist in A. lineolatus. Furthermore, when (E)-cinnamaldehyde was field tested in combination with the sex pheromone, there was no increase in male catch, but the combination attracted both males and females. Prospects for practical application are discussed.

Highlights

Plant bugs (Heteroptera: Miridae) represent the most speciesrich family of true bugs
Volatile Collection from Live Females As field cage experiments with live bugs indicated the presence of a femaleproduced sex pheromone, headspace collections were performed with single A. lineolatus females on green bean pods, and with green bean pods alone as a control, for 1 d (20–24 h) or 3 d (71–72 h)
Analyses of Female Extracts and Identification of EAG-Active Constituents Compounds from female A. lineolatus extract that consistently elicited male gas chromatographyelectroantennography (GC-EAG) were identified by GC/ mass spectrometry (GC/MS) and GC peak enhancement as hexyl butyrate [Kováts index (KI) on a polar DB-WAX column = 1420], (E)-2-hexenyl butyrate (KI = 1478) and (E)-4-oxo-2-hexenal

Summary

Introduction

Plant bugs (Heteroptera: Miridae) represent the most speciesrich family of true bugs. Due to new pest control technologies and recent changes in regulation, there has been a marked and continuous decrease in the use of broad-spectrum insecticides in agriculture. Pests considered previously to be of minor importance can become more important, as observed for genetically engineered lepidopteran-resistant crops, such as Bt-cotton (Lu et al 2010). This effect may reach beyond the intended crop. Adelphocoris species are among those pests that have gained increasing economic importance with the decrease in broadspectrum insecticide use (Lu et al 2008)

Objectives

Methods

Results

Conclusion