UBC Theses and Dissertations
Efficacy of plant essential oils and detoxification mechanisms in Choristoneura rosaceana, Trichoplusia ni, Dysaphis plantaginea and Myzus persicae Machial, Cristina Maria
The obliquebanded leafroller, Choristoneura rosaceana, and the rosy apple aphid, Dysaphis plantaginea are serious pests in apple orchards throughout North America, while the green peach aphid, Myzus persicae and the cabbage looper, Trichoplusia ni are serious pests in vegetable greenhouses. In an effort to reduce the impact of these pests on their respective crops, growers typically resort to multiple insecticide applications per year for the control of each pest. However, concerns regarding the risk of such pesticides to human and environmental health have led to renewed calls for the development of reduced risk pesticides. In the following, 17 essential oils were screened against each pest species to identify those which could be used to develop novel essential oil-based insecticides and the most toxic of these were further evaluated to determine their LC50 and LD50 values. Patchouli oil was found to be among the most toxic to all four species. Thyme oil was also toxic to both C. rosaceana larvae and D. plantaginea adults, while citronella oil demonstrated high toxicity to D. plantaginea. Garlic and lemongrass oils were also identified as potential candidates for T. ni control and lavender oil was identified as the second most toxic essential oil to M. persicae. Through this work, it was noted that there appeared to be a role for detoxification enzymes in detoxifying these essential oils. Accordingly, the detoxicative abilities of each insect and the potential role of patchouli oil in inducing these enzymes were assessed. Esterase activity was highest in M. persicae while glutathione S-transferase activity followed the order of M. persicae > D. plantaginea > C. rosaceana > T. ni. Cytochrome P450 activity was only detected in some samples, and consequently, results were less conclusive. The potential for incorporating these essential oils into an essential oil-based insecticide is discussed.
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Attribution-NonCommercial-NoDerivatives 4.0 International