Submitted to: Methyl Bromide Alternatives and Emissions Research Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: October 1, 2009
Publication Date: November 13, 2009
Citation: Walse, S.S., Tebbets, J.S., Leesch, J.G. 2009. Mapping Sulfuryl Fluoride Quarantine Control of Amyelois transitella Using Multivariate Modeling. Methyl Bromide Alternatives and Emissions Research Conference Proceedings November 10-13, 2009, San Diego, CA. p. 88.1-2. Technical Abstract: The navel orange worm (NOW), Amyelois transitella, is a cosmopolitan pest in California that is a concern to countries that import inshell nuts, particularly walnuts. Sulfuryl fluoride is currently being used to control NOW populations on walnuts, however, the conditions required to achieve requisite levels of control have not been clearly mapped out. Data indicates that there is more variability in NOW egg mortality with sulfuryl fluoride under vacuum (100 mm Hg) relative to atmospheric pressure (760 mmHg). This suggests that the concentration and time cross-product alone is not an accurate predictor of NOW egg mortality and that the effect of vacuum must be considered. Confirmatory chamber fumigations, with walnut commodity, support this interpretation. At 760 mmHg, 32 mg/L exposures over 24 h resulted in complete mortality of 1882 NOW eggs. At 100 mmHg, however, a single NOW egg out of 2039 survived a 112 mg/L exposure for 4 h. The individual and interactive effect(s) of pressure, temperature, time, and sulfuryl fluoride dose on NOW egg mortality are quantitatively delineated; a multifactorial experiment was generated and the results were analyzed using Design Expert 7.0 (Stat-Ease, Inc.). The mathematical models generated in this study serve as a valuable and practical utility to industry, as they can be used to predict NOW egg survivability during sulfuryl fluoride fumigations of stored-product dried fruit and nuts, including walnuts. This work demonstrates, for the first time, how models can be used as a tool for ensuring that targeted mortality levels are achieved during individual fumigation events. This should be particularly useful when “quarantine” control of insects (99.9986% mortality) are required to move commodity through foreign trade and marketing channels.