Insect feeding and oviposition deterrents from western red cedar foliage

Area of Science:

• Forestry
• Entomology
• Natural Products Chemistry

Background:

• Western red cedar (Thuja plicata) is a valuable timber species.
• Insect pests like the white pine weevil (Pissodes strobi) cause significant damage to conifer forests.
• Natural compounds from plants are explored for pest management strategies.

Purpose of the Study:

• To investigate the feeding deterrent activity of western red cedar foliage extracts against insect pests.
• To identify the specific compounds responsible for the deterrent effects.

Main Methods:

• Laboratory bioassays were conducted using western red cedar foliage fractions and specific insect species.
• Gas chromatography and mass spectrometry were used to analyze the leaf oil composition.
• Individual compounds were isolated and tested for feeding deterrent activity.

Main Results:

• The volatile leaf oil of western red cedar exhibited significant feeding deterrent activity against the white pine weevil.
• Monoterpene hydrocarbons, particularly (-)-3-isothujone and (+)-3-thujone, were identified as the primary active components.
• The leaf oil also showed antifeedant activity against the alder flea beetle and oviposition deterrence against the onion root maggot.

Conclusions:

• Western red cedar leaf oil contains potent feeding deterrents effective against key forest pests.
• Thujone isomers are the main active compounds, offering potential for developing natural insecticides.
• This study highlights the ecological role of plant secondary metabolites in pest resistance.