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IMPROVEMENT OF U.S. EPA MINIMUM RISK ESSENTIAL OILS’ PESTICIDE ACTIVITY THROUGH SURFACTANT ENHANCEMENT AND SYNERGY

Gillilan, Jo Anna
http://rave.ohiolink.edu/etdc/view?acc_num=osu1343666756

Abstract Details

2012, Doctor of Philosophy, Ohio State University, Horticulture and Crop Science.
Plant essential oils have been used since antiquity for many purposes, including pest control in agriculture and against nuisance pests such as mosquitoes, flies and ticks. In recent years, consumers have increasingly expressed interest in purchasing organically grown foods, as well as using natural and naturally derived materials to eradicate pests in their lawn, garden and homes. In 1996, the U.S. Environmental Protection Agency established a list, referred to as the 25(b) list, containing 31 active ingredients deemed minimum risk. Companies developing pesticides using active ingredients from the 25(b) list are exempt from federal registration requirements, providing a financial incentive to develop such products as well as fill growing consumer demand. There are 14 plant essential oils and essential oil constituents on the 25(b) list with proven pesticide properties, but there is little public information comparing efficacy of these ingredients. This study compared 14 essential oils and essential oil constituents from the 25(b) list in insecticidal and herbicidal contact bioassays: cedar oil, cinnamon oil, citronella oil, clove oil, eugenol, garlic oil, geraniol, geranium oil, lemongrass oil, mint oil, peppermint oil, rosemary oil, thyme oil, and 2-phenethyl propionate. Their performance as single active ingredients and as pairwise combinations with one another within liquid formulations was evaluated for additive or synergistic benefits. In contact insecticidal assays using 9th instar American cockroach (Periplaneta americana) nymphs, there was a significant difference in knockdown (KD) time in response to the different essential oils tested, but no synergistic effect was observed when two essential oils were combined . There was a positive correlation of insect KD time and contact angle of co-formulants that were combined with essential oils. Cinnamon, lemongrass and rosemary oils had slow KD times (>1 minute), but were significantly enhanced when paired with the surfactant system having the lowest contact angle of 60°. The 25(b) oils that should be considered for insecticide development based on performance are clove, eugenol, geraniol, geranium, peppermint and thyme oils. The same essential oils and surfactant combinations were tested for herbicide burndown on dandelions (Taraxacum officianale) and smooth crabgrass (Digitaria ischaemum). There were significant differences in herbicidal activity of the essential oils, but again no synergistic effect was observed when two essential oils were combined. A novel discovery of synergy was made when herbicidal activity was greatly enhanced by combining essential oils with a surfactant system containing a non-herbicidal rate of sodium caprylate, a fatty acid salt. The 25(b) oils with the highest weed injury were cinnamon, citronella, eugenol, geraniol, geranium, peppermint and thyme oils. The findings of these experiments suggest that all 25(b) essential oils except garlic oil can be formulated into effective pesticides. Targeting a low contact angle surfactant system can enhance insecticidal activity of these oils, while the use of sodium caprylate can speed phytotoxic symptoms when used as herbicides.
David Gardner, PhD (Advisor)
David Shetlar, PhD (Committee Member)
Karl Danneberger, PhD (Committee Member)
Brian McSpadden Gardener, PhD (Committee Member)
Rami Soufi, PhD (Committee Member)
177 p.
Agriculture
synergy; insecticide; herbicide; essential oils

Recommended Citations

Citations

  • Gillilan, J. A. (2012). IMPROVEMENT OF U.S. EPA MINIMUM RISK ESSENTIAL OILS’ PESTICIDE ACTIVITY THROUGH SURFACTANT ENHANCEMENT AND SYNERGY [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343666756

    APA Style (7th edition)

  • Gillilan, Jo. IMPROVEMENT OF U.S. EPA MINIMUM RISK ESSENTIAL OILS’ PESTICIDE ACTIVITY THROUGH SURFACTANT ENHANCEMENT AND SYNERGY. 2012. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1343666756.

    MLA Style (8th edition)

  • Gillilan, Jo. "IMPROVEMENT OF U.S. EPA MINIMUM RISK ESSENTIAL OILS’ PESTICIDE ACTIVITY THROUGH SURFACTANT ENHANCEMENT AND SYNERGY." Doctoral dissertation, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1343666756

    Chicago Manual of Style (17th edition)

osu1343666756
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© 2012, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.
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