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Critical Analysis of Methyl Bromide, Sulfuryl Fluoride, and Heat Treatment in Disinfecting Food-Processing Facilities


Concerns about the ozone-depleting abilities of methyl bromide have resulted in its phase-out in 2005 in the US, and only certain groups were allowed to use MB under the Critical Use Exemptions Category. The food industry, which uses MB as a structural fumigant, has made efforts to seek alternative fumigants and pest management strategies. However, limited information is available, especially on the cost-effectiveness of alternative strategies for the food industry to fully embrace them. The current proposal addresses some issues and challenges that should be addressed through research to make alternative strategies viable and cost effective.<P> The proposed project goals are to show a reduction in methyl bromide (MB) usage as a structural treatment in food-processing facilities by facilitating adoption of MB alternatives strategies such as sulfuryl fluoride (SF), heat treatment and integrated pest management (IPM) approaches through pilot and commercial scale evaluations. Documenting cost-effectiveness of each strategy is central to adoption of MB strategies. <P>The proposed work also involves quantifying effects of structure air-tightness and weather conditions on fumigant emissions from and dispersion around fumigated structures, an aspect useful in defining buffer zones for MB and SF fumigants. The effectiveness of MB and alternative strategies to food industry stakeholders will be documented through educational programs and demonstrations at Kansas State pilot flour mill facilities and validation of pilot mill test results in commercial facilities in stakeholder-managed trials. <P>The project involves using bioassays with insects and novel models already developed to optimize and evaluate efficacy of MB compared to SF and heat on red flour beetle life stages in the K-State Hal Ross flour mill, and subsequently verify optimization tactics in commercial food-processing facilities subjected to MB, SF, and heat and other IPM tactics and gauge its impact on red flour beetle populations, a common and severe pest associated with food-processing facilities.<P> Another objective of the project involves performing an economic analysis of structural treatments and physical control methods both in the Hal Ross (pilot) mill and in 15 commercial facilities, and such an analysis is essential for acceptance and adoption by the food industry. Dissemination of our science-based information to stakeholders through demonstration, hands-on training programs, and publications through various formats is central to ensure adoption. The degree of adoption will be measured by periodic contact of industry stakeholders.

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Non-Technical Summary: The food-processing industry and National Pest Management Association (NPMA) stakeholders applying for critical use nominations in light of the 2005 phase out of methyl bromide (MB) in the US have cited several limitations for not fully utilizing sulfuryl fluoride (SF) and heat as MB alternatives. They include questionable efficacy of SF and heat when compared with MB based on current data, lack of solid economic assessment to make alternatives viable, geographic location (related to temperature) effects that make use of SF or heat unsuitable, lack of effectiveness against certain life stages of pests (SF and eggs), increased knowledge and skill required to use Fumiguide (SF), issues related to gas-tightness of facilities (emissions and buffer zones), extended treatment times with heat (>24 h), and possible adverse effects of heat on structural components of facilities and corrosion effects of phosphine (ECO2FUME) on electronic equipment. Previous comparisons on the effectiveness of MB, SF, and heat in managing stored-product insects were not accurate because data were collected from different facilities receiving these treatments at different times of the year. Furthermore, treatment effectiveness is generally gauged by comparing captures of adult insects in traps before and after an intervention, making it difficult to accurately and directly sample the true insect populations in a facility. The use of traps provides some measure of treatment effectiveness, but basing treatment effectiveness exclusively on adult captures is not valid because it is possible for traps to capture adults immigrating into a facility after a treatment. A better approach would be to compare MB, SF, and heat treatment effectiveness in the same facility under similar environmental conditions with direct assessment of mortality of all life stages of a pest species, and data are currently lacking on this aspect. Therefore, in this proposal we intend to perform these tests in the Kansas State University Hal Ross flour mill. These data, along with economic analysis and additional monitoring in commercial facilities, will provide the first accurate side-by-side evaluation of cost-effectiveness of MB, SF, and heat. The multi-institution and multi-year project addresses two of the 15 critical use nominations (5 and 11) for 2009 and beyond, and addresses the concerns raised by the food industry and NPMA. This integrated project supports discovery and implementation of practical pest management alternatives to MB through research in pilot scale and commercial facilities, and involves detailed extension and educational activities that promote adoption of MB alternatives by representatives of the food industry and NPMA. <P> Approach: The effectiveness of MB, SF, and heat will be evaluated in the K-State Hal Ross pilot flour mill. All three treatments will occur within a months time, and each treatment will be replicated three times. Temperatures and humidity levels will be measured during heat treatment to evaluate heat distribution patterns. Levels of MB and SF and environmental conditions will be monitored hourly to calculate and ensure proper Ct values were obtained for commercial insect kill. Treatment effectiveness will be evaluated by exposing red flour beetle eggs, larvae, pupae, and adults in whole wheat flour diet at two density levels, to simulate sanitation effects on insect survival. Survival of insects subjected to various treatments will be incorporated into a population model to simulate rebound rate as a function of infestation level, sanitation and immigration rate. A 3D computational fluid dynamics (CFD) model will be used to understand influences of environmental conditions on fumigant behavior in different types of food-processing facilities. A Heat Treatment Calculator (HTC) will be used to estimate heat energy requirements and costs associated with the gas heat treatment. The estimated energy requirements and costs will be compared with observed values. The Efficacy Assessment in Real-Time during Heat treatment (EARTH) software will be tested extensively in the pilot mill to predict survival of first instars of the red flour beetle (the most heat tolerant of all stages and species of insects evaluated) in real time as a function of time-dependent temperature profiles, acquired remotely using wireless sensors, prior to practical use and additional verification in commercial facilities. The CFD model, HTC, EARTH, and red flour beetle population model will be evaluated in 15 commercial food-processing facilities during 2010-2011 to predict gas emissions during structural fumigation, heat energy requirements, minimum time required to kill first instars of red flour beetles, and evaluate impact of treatments on population rebounds, respectively. Cost budgets and capital budgeting techniques will be used to compute cost per cwt of flour produced for each control strategy. Optimization models will be used to examine the tradeoff between insect mortality and cost across control strategies. This model examines the tradeoff between cost and total deviations below a target insect mortality rate. Deviations for each control strategy replication will be measured using a target mortality goal of 100%. Research results will be transferred to food industry stakeholders through seminars, university websites, food industry association meetings, extension publications, trade journals, hands-on demonstrations, professional meetings, and scientific publications. The number of hits to websites, requests for information, and participants attending IPM workshops, and changes in practices of these participants in adopting MB alternatives will be used to evaluate extension and education program success.

Subramanyam, Bhadriraju
Kansas State University
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