Identification of limonene as a potential kairomone of the harlequin ladybird Harmonia axyridis (Coleoptera: Coccinellidae)

Ammar Alhmedi,Frédéric Francis,Eric Haubruge

doi:10.14411/eje.2010.062

Abstract

Chemical cues involved in both host location and oviposition by Harmonia axyridis Pallas (Coleoptera: Coccinellidae) were investigated in laboratory and field experiments. Among the five volatiles tested in a four-arm olfactometer ((E)-β-farnesene, β-pinene, β-caryophyllene, cis-3-hexen-1-ol, and limonene), gravid H. axyridis females were significantly attracted to limonene and β-caryophyllene. These two chemicals also increased H. axyridis oviposition on plants. Attraction of H. axyridis towards limonene was further tested under field conditions using controlled-release dispensers. (E)-β-farnesene, a major aphid alarm pheromone and a potential predator kaironome, was also tested in this study. Field data confirmed those from laboratory studies concerning the attraction of H. axyridis towards limonene and a lack of response to (E)-β-farnesene. In contrast, the aphid predator Episyrphus balteatus DeGeer (Diptera: Syrphidae) was attracted to (E)-β-farnesene but not to limonene. These findings indicate that H. axyridis uses chemicals, such as limonene, for prey location and oviposition, and support the potential use of volatiles in the management of H. axyridis.

Highlights

Semiochemicals released by plants in response to herbivore attack and the subsequent use of these chemical signals by natural enemies to locate these herbivores is a widespread phenomenon observed in various tritrophic systems
Similar evidence was found for semiochemicals, e.g. (E)-E-farnesene, released by herbivores, e.g. aphids, in response to natural enemy attack; natural enemies use these chemical signals to locate their prey, e.g. the ladybird species Coccinella septempunctata L. (Al Abassi et al, 2000; Ninkovic et al, 2001) and Adalia bipunctata L. (Hemptinne et al, 2000; Francis et al, 2004), and the hoverfly Episyrphus balteatus DeGeer (Francis et al, 2005a; Verheggen et al, 2008) were attracted to (E)-E-farnesene emitted from aphids
When observing the first zone entered, female H. axyridis did not exhibit any significant preference for the volatiles compared to controls, (F2 = 4.80, d.f. = 3, P = 0.187 for limonene; F2 = 1.60, d.f. = 3, P = 0.659 for (E)-E-farnesene; F2 = 6.05, d.f. = 3, P = 0.109 for E-caryophyllene; F2 = 0.40, d.f. = 3, P = 0.940 for E-pinene; F2 = 2.00, d.f. = 3, P = 0.572 for cis-3-hexen-1ol)

Summary

Introduction

Semiochemicals released by plants in response to herbivore attack and the subsequent use of these chemical signals by natural enemies to locate these herbivores is a widespread phenomenon observed in various tritrophic systems. Ladybirds are subjected to various chemical blends when searching for an oviposition site These blends consist of plant and insect semiochemicals such as (E)-E-farnesene as the main component of the alarm pheromone of most aphid species, E-pinene, and limonene (Nault et al, 1973; Francis et al, 2005b)

Methods

Results

Conclusion