Page 45 - Volume 2,Issue 2, July 2009

Hellenic Plant Protection Journal

2:

91-99, 2009

Sublethal effects of three essential oils on the development,

longevity and fecundity of

Acanthoscelides obtectus

(Say)

(Coleoptera: Bruchidae)

D.P. Papachristos

1

and D.C. Stamopoulos

2

Summary

Acanthoscelides obtectus

larvae and pupae were exposed to three levels (LC

10

, LC

40

and LC

70

)

of lavender, rosemary and eucalyptus essential oil vapours. The exposure of larvae and pupae to sub-

lethal doses of essential oil vapours resulted in increased larval and pupal developmental time and re-

duced longevity and fecundity of the emerged female adults. The observed effects depended on the

insect stage and sex as well as the essential oil tested. In all cases no delayed mortality was observed.

Additional keywords

:

Eucalyptus globulus, Lavandula hybrida, Rosmarinus officinalis,

volatiles

1

Department of Entomology and Agricultural Zoolo-

gy, Benaki Phytopathological Institute, 8 St. Delta Str.,

145 61, Kifissia (Athens) Greece.

2

Laboratory of Zoology and Aquatic Entomology, De-

partment of Agriculture, Ichthyology and Aquatic En-

vironment, School of Agriculture, University of Thes-

saly, Volos, Greece.

Corresponding author:

D.Papachristos@bpi.gr

gion.

Although the insecticide properties of

the aforementioned essential oil vapours

have been well documented and their LC

50

values were established, their possible sub-

lethal effects have not been thoroughly ex-

plored even though it is well known that

many target insects do not receive the ap-

propriate lethal dose during fumigations. In

fact, insects exposed to sublethal doses of

insecticides may display a variety of symp-

toms including reduction in growth rate,

life span, pupal weight and adult fecundity

and fertility (3, 4, 5, 9, 10, 15). In contrast, ad-

vantageous effects have also been record-

ed; these include increased immature stage

weight, developmental rate and adult fertil-

ity (27). Therefore, the consequences of sub-

lethal exposure have important implications

on insect management and from this point

of view it is worthy to elucidate such type of

effects exhibited by the essential oil vapours

(14). Moreover, as Karr and Coats (13) point-

ed out, when monoterpenoids are investi-

gated as potential insecticides, direct toxici-

ty as well as appraisal of negative effects on

biotic potential must be considered in the

assessment of overall efficacy.

The aim of this study was to investigate

the effects of sublethal doses of lavender,

rosemary and eucalyptus essential oil va-

Introduction

In recent years, the trend towards reducing

reliance on synthetic insecticides for the con-

trol of stored products pests has oriented

worldwide research in the insecticidal prop-

erties of different essential oils that often be-

have like conventional fumigants exhibiting

strong adverse effects on both immature and

adult stages. In fact, these compounds may

act as fumigants, repellents, antifeedants

and may also affect some biological parame-

ters such as growth rate, life span and repro-

duction (11, 12, 16, 18, 19, 20, 21, 23, 26).

Previous studies (18, 19) have estab-

lished the strong toxic activity of the essen-

tial oil vapours of

Lavandula hybrida

Rev. (La-

miacae),

Rosmarinus officinalis

L. (Lamiacae)

and

Eucalyptus globulus

Labill. (Myrtacae)

against the immature stages of

Acanthos-

celides obtectus

(Say), the most destructive

pest of

Phaseolus vulgaris

L. (kidney bean),

one of the most important food pulses in

South America and the Mediterranean re-