Evaluation of the efficacy of plant-based essential oil blends for the control of leafrollers on apples

Project Code: BPI07-120

Project Lead

Murray Isman - University of British Columbia

Objective

To establish efficacy of various essentials oils and formulations against leafroller pests of apples, and to evaluate the potential for cross resistance to these materials in insects with known resistance to organophosphate pesticides

Summary of Results

The obliquebanded leafroller, Choristoneura rosaceana, has become an increasingly important apple pest in the Okanogan Valley and throughout many apple producing regions of North America. Efforts to find suitable control options are ongoing in order to supplement the current limited arsenal. Accordingly, a study was conducted to determine the potential role for the use of essential oil-based products as a new source of control for this pest. As part of the Biopesticide Initiative, the objectives addressed by this research were primarily to find essential oils and/or formulations which possess insecticidal effects. Additional objectives which were to be addressed include determining the antifeedant properties of these compounds, testing select oils for cross-resistance in leafrollers with known resistance to organophosphate pesticides and to use the results to pursue label expansion or registration of effective products if warranted.

In order to address the above objectives, a variety of essential oils and formulated products were tested using bioassays in which neonate larvae were sprayed directly with various concentrations of each treatment. Eighteen essential oils, four carrier oils, and two formulated products were tested in total:

Essential Oils

  • Camphor wood oil (Cinnamomum camphora)
  • Cedarwood oil (Juniperus virginiana)
  • Cinnamon oil (Cinnamomum zeylanicum)
  • Citronella oil (Cymbopogon spp.)
  • Clove bud oil (Eugenia caryophyllata)
  • Eucalyptus oil (Eucalyptus globules)
  • Garlic oil (Allium sativum)
  • Grapefruit oil (Citrus paradise)
  • Lavender oil (Lavendula angustifolium)
  • Lemongrass oil (Cymbopogon nardus)
  • Marjoram oil (Thymus masticina)
  • Niaouli oil (Melaleuca viridiflora)
  • Patchouli oil (Pogostemum cablin)
  • Peppermint oil (Mentha × piperita)
  • Pennyroyal oil (Mentha pulegium)
  • Rosemary oil (Rosmarinus officinalis)
  • Tea tree oil (Melaleuca alternifolia)
  • White thyme oil (Thymus vulgaris)

Carrier oils

  • Cottonseed oil (Gossypium spp.)
  • Sesame oil (Sesamum indicum)
  • Soybean oil (Glycine max)
  • Sunflower oil (Helianthus annuus)

Formulated products, source EcoSMART Technologies, Inc

  • EcoTro
  • Prototype Formulation ECX

Among the essential oils listed above, patchouli oil was determined to be the most toxic to leafrollers with an average LC50 of 0.227%, while white thyme oil was the next most toxic with an average LC50 of 0.524%. In both cases, use of the synergist, piperonyl butoxide (PBO) or the natural PBO analog, camphor wood oil, reduced the LC50 substantially. None of the carrier oils, nor EcoTrol was particularly effective against the leafrollers (LC50 for EcoTrol was over 10%). Prototype Formulation ECX, an essential oil/pyrethrum based formulation, was the most effective, with an LC50 of 0.068% as an aqueous emulsion. Further work is required before any of these active ingredients can be formulated and the presubmission consultation process can begin. The ECX product is being considered for US EPA registration as a biopesticide, which could facilitate regulatory approval in Canada.

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