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Abstract
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The tomato leafminer, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is one of the major
insect pests of solanaceous crops especially tomatoes. As plants contain secondary metabolites
with protective properties against unwanted agents, they can be used as insecticides after
extraction from plants as essential oils (EOs). In this study, essential oils of three savory species,
including Satureja khuzestanica, S. bachtiarica, and S. rechingeri were extracted. Analyzing the
chemical compositions via gas chromatography–mass spectrometry (GC/MS) revealed that geraniol
was the main component of all essential oils. The volatile activity of these three savory species
on the fourth instar larvae of T. absoluta during 24 h, indicated that LC50 values of S.
khuzestanica, S. bachtiarica, and S. rechingeri oils were 17.51, 25.03, and 34.33 lgL1(air), respectively.
Enzyme assays in vivo using alpha-naphthyl acetate (a-NA) as a substrate, showed that in
the fourth instar larvae treated with 10 percent lethal concentration (LC10), general esterases of
these larvae increased significantly in all treatments (p<.05). Polyacrylamide gel electrophoresis
with a solution mixture of both substrates (a-and ß-NA) clarified three bands of esterases.
However, this method failed to show any sublethal effects of the oils (LC10 value) on the larvae
esterase bands. Considering the potential toxicity of these three species of Satureja essential oils
to the tomato leafminers due to existence of several secondary metabolites, we can expect that
new bio-pesticides can be developed from these promising plants in near future.
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