Plant secondary metabolites play an important role in plant-insect interactions and therefore such compounds may have
insecticidal or biological activity against insects. Fumigant toxicity of essential oils of leaves and fruits from oriental
arborvitae (
Platycladus orientalis
[L.] Franco) (Cupressaceae) was investigated against adults of cowpea weevil
(
Callosobruchus maculatus
Fab.), rice weevil (
Sitophilus oryzae
L.), and red flour beetle (
Tribolium castaneum
Herbst).
Fresh leaves and fruits were subjected to hydrodistillation using a Clevenger-type apparatus and the chemical composition
of the volatile oils was studied by gas chromatography-mass spectrometry (GC-MS). Twenty-six compounds (92.9%) and
23 constituents (97.8%) were identified in the leaf and the fruit oils, respectively. The major components of both leaves and
fruits oils were α-pinene (35.2%, 50.7%), α-cedrol (14.6%, 6.9%) and Δ-3-carene (6.3%, 13.8%), respectively. Both oils
in the same concentration were tested for their fumigant toxicity on each species. Results showed that leaf oils were more
toxic than fruit oils against three species of insects.
Callosobruchus maculatus was more susceptible than
S. oryzae and
T.
castaneum. LC
50 values of the leaf and the fruit oils at 24 h were estimated 6.06 and 9.24 μL L
-1 air for
C. maculatus, 18.22
and 21.56 μL L
-1 air for
S. oryzae, and 32.07 and 36.58 μL L
-1 air for
T. castaneum, respectively. These results suggested
that
P. orientalis oils may have potential as a control agent against
C. maculatus,
S. oryzae, and
T. castaneum.
