Author
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Hollingsworth, Robert |
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HAMNETT, ROBERT - University Of Hawaii |
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Submitted to: Acta Horticulturae
Publication Type: Proceedings Publication Acceptance Date: 5/17/2010 Publication Date: N/A Citation: N/A Interpretive Summary: Waxy insects such as mealybugs and scale insects are difficult to kill using contact insecticides because the waxes produced by these insects form a physical barrier preventing chemical penetration. Exported horticultural commodities can be rejected or destroyed if found infested at destination. Post-harvest dips of soaps and paraffinic oils can be used to control these pests, but these remedies are less effective and cause too much damage to plant leaves compared with properly formulated emulsions of essential oils and terpenes (hydrocarbon chemicals found in essential oils) such as peppermint oil and limonene. In bioassays with longtailed mealybugs [Pseudococcus longispinus (Targioni Tozzetti)] we have found that potassium salts of fatty acids (insecticidal soap) or polysorbate 80 (Tween 80®) can be used to create water-based, plant-safe emulsions of 1% peppermint oil or 1% limonene that are effective in controlling waxy insects. When sodium lauryl sulfate and citric acid are included in the formulation containing the essential oil or terpene, efficacy increases dramatically. Many types of plant leaves will tolerate this enhanced mixture, which penetrates and kills mealybugs within seconds. The mode of action for these emulsions are discussed, as well as the regulatory outlook for the post-harvest use of such mixtures. Technical Abstract: Waxy insects such as mealybugs and scale insects are difficult to kill using contact insecticides because the waxes produced by these insects form a physical barrier preventing chemical penetration. Exported horticultural commodities can be rejected or destroyed if found infested at destination. Post-harvest dips of soaps and paraffinic oils can be used to control these pests, but these remedies are relatively ineffective and/or phytotoxic in comparison to properly formulated oil-in-water emulsions of essential oils and terpenes such as peppermint oil and limonene. In bioassays with longtailed mealybugs [Pseudococcus longispinus (Targioni Tozzetti)] we have found that potassium salts of fatty acids or polysorbate 80 can be used to create aqueous, plant-safe emulsions of 1% peppermint oil or 1% limonene that are effective in controlling waxy insects. When sodium lauryl sulfate and citric acid are included in the formulation containing the essential oil or terpene, efficacy increases dramatically. Many types of plant leaves will tolerate this enhanced mixture, which penetrates and kills mealybugs within seconds. The mode of action for these emulsions are discussed, as well as the regulatory outlook for the post-harvest use of such mixtures. |
