LE3 .A278 2022

2022

Hillier, Kirk
Faraone, Nicoletta

Acadia University

Master of Science

Masters

Biology

Biology

Tetranychus urticae Koch (the two-spotted spider mite) is an agricultural pest with a host range of over 1100 species of plants. Tetranychus urticae has rapidly developed resistance to a variety of synthetic chemical pesticides due to its high fecundity and short generation time. Plant essential oils have been recognized as a novel natural source of pest control that have a reduced impact to the environment and human health from synthetic pesticides, and which may provide a viable alternative for managing T. urticae. The present study investigates the potential of natural-based products as repellents and miticides. A novel electrophysiological approach was developed to record the electrophysiological response from T. urticae. Additionally, a novel two-choice behavioural assay was designed to determine if T. urticae is attracted or repelled by various compounds. Both electrotarsograms and behavioural assays were used to identify compounds detected by T. urticae. Using Gas Chromatogram-Flame Ionization Detection (GC-FID) linked to electrotarsographic detection (GC-ETD), it was determined that T. urticae is sensitive to eucalyptol, thymol, and linalool, which are terpenoids commonly found in essential oil mixtures from many plant species. In addition, the study screened volatile organic compounds with different functional groups and found that T. urticae is sensitive to a series of carboxylic acids and a series of aldehydes which are typically detected by ionotropic receptors. By conducting two-choice behavioural assays, it was determined that T. urticae is repelled by many essential oil mixtures, carboxylic acids, and aldehydes. To further identify compounds of behavioral relevance for T. urticae, collections of volatiles from mites were made using thermal desorption linked with GC-MS analysis. Finally, the project investigated alternative uses and potential non-target impacts of novel commercial product (product 102) for acaricide use. Product 102 was tested as a potential fungicide against Botrytis cinerea Persoon and Cladosporium herbarum Persoon. To investigate potential non-target impacts, acute contact toxicity tests were conducted using 102 on Bombus impatiens Cresson.

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https://scholar.acadiau.ca/islandora/object/theses:3879