USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 1

METHYL BROMIDE CRITICAL USE RENOMINATION FOR POSTHARVEST -- DRY CURED PORK PRODUCTS

NOMINATING PARTY: The United States of America

FILE NAME: USA CUN16 POST HARVEST -- DRY, CURED PORK PRODUCTS

BRIEF DESCRIPTIVE TITLE OF NOMINATION:

Methyl Bromide Critical Use Nomination for Post Harvest Use on Dry Cured Pork Products

(Submitted in 2014 for 2016 Use Season)

STRUCTURE, COMMODITY OR OBJECT TREATED:

This sector is for the production of dry cured pork products, such as country hams. These are 

produced primarily in the southern U.S. This sector has no known viable alternative currently 

available. 

QUANTITY OF METHYL BROMIDE REQUESTED IN EACH YEAR OF 

NOMINATION:

TABLE 1: QUANTITY OF METHYL BROMIDE REQUESTED IN EACH YEAR OF NOMINATION

YEAR NOMINATION AMOUNT (KILOGRAMS)

2016 3,240 kg

(Details on this page are requested under Decision Ex. I/4(7), for posting on the Ozone Secretariat website under 

Decision Ex. I/4(8).) 

In assessing nominations submitted in this format, TEAP and MBTOC will also refer to the original nomination on 

which the Party’s first-year exemption was approved, as well as any supplementary information provided by the 

Party in relation to that original nomination. As this earlier information is retained by MBTOC, a Party need not 

re-submit that earlier information. 

NOMINATING PARTY CONTACT DETAILS:

Contact Person: Federico San Martini, Ph.D.

Title: Foreign Affairs Officer

Address: Office of Environmental Policy

U.S. Department of State

2201 C Street, N.W. Room 2657

Washington, D.C. 20520 

U.S.A.

Telephone: (202) 647-3819

Fax: (202) 647-1052

E-mail: SanMartiniFM@state.gov

Following the requirements of Decision IX/6 paragraph (a)(1) United States of America has determined that the 

specific use detailed in this Critical Use Nomination is critical because the lack of availability of methyl bromide for 

this use would result in a significant market disruption. ■ Yes  No
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 2

Signature Name Date

Title: 

CONTACT OR EXPERT(S) FOR FURTHER TECHNICAL DETAILS:

Contact/Expert Person: Yu-Ting Guilaran

Title: Director

Address: Biological and Economic Analysis Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W. Mailcode 7503P

Washington, D.C. 20460

U.S.A.

Telephone: (703) 308-0052

Fax: (703) 308-8091

E-mail: Guilaran.Yu-Ting@epa.gov

LIST OF DOCUMENTS SENT TO THE OZONE SECRETARIAT IN OFFICIAL NOMINATION PACKAGE:

1. PAPER DOCUMENTS: 

Title of paper documents and appendices

No. of pages Date sent to Ozone 

Secretariat

2. ELECTRONIC COPIES OF ALL PAPER DOCUMENTS: 

*Title of each electronic file (for naming convention see notes above)

No. of 

kilobytes 

Date sent to Ozone 

Secretariat

USA CUN16 Post Harvest Ham

* Identical to paper documents
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 3

METHYL BROMIDE CRITICAL USE RENOMINATION FOR POSTHARVEST -- DRY CURED PORK PRODUCTS

1. SUMMARY OF NEED FOR METHYL BROMIDE AS A CRITICAL USE

Currently there are no viable alternatives to methyl bromide for the dry cured pork industry. The 

United States has an active research program on methyl bromide alternatives for dry-cured pork 

products. Through that program, researchers have investigated all the avenues recommended by 

MBTOC, but none have demonstrated commercial viability at this time. Final results are not yet 

available and research on these suggestions recommended by MBTOC continues. Preliminary 

work by Zhao et al (2012a) indicates that there may be other methods to control mites. The 

United States is committed to continued research in this area and remains hopeful that such 

research efforts will help identify and develop commercially viable alternatives to methyl 

bromide for use in this sector. At the time of this nomination, there are no known registered 

alternatives for use on dry cured pork in the United States that provide the same level of mite

control as methyl bromide. U.S. regulations do not permit the introduction into interstate 

commerce of dry-cured pork products contaminated with mites. Therefore, methyl bromide 

remains critical to this industry. 

TABLE 2. NOMINATION AMOUNT 

2. SUMMARIZE WHY ALTERNATIVES ARE NOT FEASIBLE

This industry currently has no viable chemical or non-chemical alternative available. Although 

IPM measures have minimized the frequency fumigation is needed, it has not eliminated the 

need for fumigation. Therefore, methyl bromide remains critical to this industry. 

HAM

 Sector Total 

Quantity Requested for 2015: Amount (kgs) 3,240

Quantity Recommended by 

MBTOC/TEAP for 2015 : Amount (kgs) 3,240

Amount (kgs) 3,240

Volume (1000 m3) not stated

Rate not stated

Transition from 2015 

Baseline Adjusted Value Percentage (%) 0%

Amount (kgs) 3,240

Volume (1000 m3) see Table 3

Rate see Table 3

Quantity Authorized by 

Parties for 2015:

Quantity Required for 

2016 Nomination:

SECTOR
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3. UPDATE OF RESEARCH RESULTS SHOWING EFFICACY OF ALTERNATIVES

University researchers in Kansas, Mississippi and Oklahoma are investigating the management 

and control of arthropod pests that infest dry cured pork products during the aging process. This 

interdisciplinary and multi-institutional group is funded primarily by the USDA competitive 

grants program titled “Methyl Bromide Transitions.” 

Latest Research Results

Tyrophagus putrescentiae, the ham mite, is the most serious arthropod pest of southern dry cured 

hams in the USA. Work at Kansas State University (KSU) developed a trap for use in integrated 

pest management, IPM (summarized recently by Amoah et al. 2013). The trap consists of a 90 

mm disposable plastic Petri dish that is painted black on the entire outer surface. Around the 

sidewall of the dish are eight evenly spaced holes, approximately 0.5 mm in diameter, at 2 mm 

above the bottom of the dish for entry of responding mites. The lure or bait, consisting of a 10 

mm high by 25 mm dia circular plug of mite rearing diet jelled in agar, is placed inside the center 

of the trap. Mites respond to the baited dishes, enter the holes in the side wall, and feed on the 

diet plug where they also mate and lay eggs. Laboratory studies confirmed that traps baited with 

food diet were very effective at detecting mites compared to unbaited traps. During 2012-2013 

mite populations were monitored in three commercial ham curing/aging facilities using 20 traps 

distributed evenly throughout the buildings for consecutive one-week periods. Mite numbers in 

traps varied from zero to several hundred in each week, consecutive weekly trapping suggested a 

seasonal variation in mite populations, and the spatial distribution of traps with or without mites 

demonstrated that certain areas of a given facility consistently had higher mite activity than other 

areas. Mite numbers in traps confirmed that fumigation in certain circumstances caused severe 

reduction in mite populations, and showed that mites would slowly increase in numbers and 

activity following fumigation.

KSU research in 2013 focused on the sensitivity for mite detection with these traps and the role 

of environmental factors such as temperature, relative humidity, trap placement relative to 

structural features, proximity of traps from a source of mites and general trap design on trap 

efficacy (Amoah et al. 2013). The standard trap was deployed in four retail facilities close to 

Kansas State University, including a pet store, an organic grocery store, a large “big box” 

department store and a farm supply store in order to have a near-by study site. Mites were 

detected only at the farm supply store. Of twenty traps evenly spaced throughout the retail area, 

mites were consistently trapped only in one specific area. Traps were also deployed in three 

small rooms at our KSU laboratory in which we released an open colony of mites at one end of 

the floor and traps were arranged in three consecutive 1 m intervals away from the food source, 

either along one side wall or in the center of the floor. Results suggest that mites can be detected 

3 m from a population source within minutes to hours from the time of deployment and that 

room wall edges may be important for orientation of mites to traps. Experiments are planned 

that will evaluate various commercial designs of stored product beetle traps that should also 

capture mites. Simple laboratory rooms and the farm supply store with a localized mite 

population will be used to correlate mite trap counts to direct measures of mite density derived 

from defined floor samples of mites and dust collected in a defined area. Monitoring data of T. 
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putrescentiae populations using traps will be important information to aid in IPM decisionmaking.

To date very little information is available on the potential for non-fumigant chemicals to control 

ham mites. Laboratory studies were conducted to assess the potential of food grade 

preservatives to function in coatings on hams to prevent mite infestation and also for registered 

and experimental pesticides for applying a residual treatment to environmental surfaces to kill 

mites (reported by Abbar et al. 2013). A bioassay with food preservatives was conducted, in 

which pieces of ham or whole hams were dipped in or sprayed with a given compound and then 

exposed to 20 adult mites for 14 days, after which the total resulting population of surviving 

nymphs and adults was determined. Propylene glycol, the preservative ethoxyquin and a mixture 

of short-chain hydrocarbons proved effective at preventing mite reproduction on small ham 

pieces. A simulated field study was conducted in which whole 27-lb green hams were coated

with cure mix from Rebel Butcher Supply and then each sprayed with 28 g of 100% propylene 

glycol, PG. Hams were again treated with cure mix at 8 and 18 days after the first application 

then washed and cold-smoked at day 21. After smoking, single hams were sprayed with PG 

either 4 times at 4-week intervals, at 3 week intervals for 5 times and most frequently at 2-week 

intervals for 7 sprays. One-inch cubes were taken from outer slices of each ham and subjected to 

mite reproduction challenge. The non-PG hams and those treated at 4-week or 3-week intervals 

produced high numbers of mites, but cubes from the ham treated at 2 week intervals produced 

significantly fewer mites.

Laboratory experiments of registered and experimental pesticides utilized a bioassay in which 20 

adult mites were released inside a ventilated glass vial that had been previously treated with 35 ul 

of a diluted test compound. Mites were allowed to walk on the treated surface for 24 hrs, after 

which they were moved to clean vials with food for 24 hrs and then assessed for mortality. Each 

experiment had a solvent-only control and up to 3 concentrations of the test compound (0.5 X, 1 

X and 2 X the EPA label rate). Of eight active ingredients tested an experimental mixture of 

short-chain hydrocarbons and registered formulations of deltamethrin, chlorfenapyr and a 

mixture of deltamethrin with chlorpyrifos-methyl had very high mite mortality at the recommend 

label rates and at half the label rates. Results to date with food-safe preservatives and with 

commercial pesticides currently registered by EPA for surface treatments in storage facilities 

show great promise for IPM of ham mite; however, further work is needed to validate the 

effectiveness of these potential alternatives. 

Methyl bromide has been the most effective, and essentially the only, pest control method used 

by the dry cured ham industry to manage ham mite infestations. The potential loss of methyl 

bromide calls for an effective alternative in the form of a fumigant that can be applied over a few 

days at most, has no negative impact on food quality and can effectively reduce or eliminate mite 

infestation and other arthropod pests with minimal cost relative to the benefit of protecting the 

ham products. In past years the fumigant sulfuryl fluoride was evaluated for the ham mite at 25o

C for 48 hrs and did not eliminate the egg stage to the level that would effectively control pest 

mite populations. However, in laboratory testing, phosphine was effective against all life stages 

within the label rates of the fumigant, and dried meats are already listed on the application label.
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 6

Drs. Schilling and Phillips participated in a commercial fumigation of a working ham production 

facility with phosphine gas in early 2013 (Phillips 2013). Two rooms were selected for treatment 

and each had several hundred hams that were in the late first or second year of aging. 

Magnesium phosphide was chosen as the application material because it produces twice as much 

hydrogen phosphide, PH3, and at a faster rate, than does aluminum phosphide. Each room was 

well sealed and access of gas was restricted to exclude electrical and heating-air conditioning 

systems from exposure. Gas concentrations of 1500 ppm and 700 ppm were reached within 12 

hours of initiation in each room, and these levels were maintained for the duration of the 48 hr 

treatment. Another full day was required for de-gassing and clearance of the facility before

workers were allowed back in. Ventilated mite colony jars placed in treated and untreated spaces 

during the PH3 application confirmed that mortality of ham mites was very high in the treated 

rooms. Unfortunately, corrosion to electrical wiring and equipment was discovered as 

unacceptably high about 21 days after the fumigation. Because of this corrosion issue with 

phosphine, it is not considered a viable alternative for the industry at this time. Future work 

needs to be done to properly prepare ham production facilities for the corrosion potential of 

phosphine gas before application of this fumigant is recommended as a methyl bromide

alternative for country hams.

Research continues on fumigation alternatives for ham mites. The researchers have revisited 

sulfuryl fluoride to determine if its efficacy against mite eggs could be improved at higher 

fumigation temperatures and longer gas exposure times. Preliminary studies suggest that a 

treatment temperature of 35oC for 48 hrs at a high sulfuryl fluoride concentration can control all 

ham mite life stages. 

A New Methyl Bromide Transition Grant

The USDA-Methyl Bromide Transition program funded a multi-institutional and multidisciplinary project led by Dr. Phillips (KSU), Dr. Schilling (Mississippi State Univ.) and Dr. 

Adam (Oklahoma State University) for an Integrated Project to both conduct research into 

various methods of integrated pest management (IPM) of southern dry cured hams that include 

methyl bromide alternatives, and to develop educational materials and deliver extension 

programs for producers and the pest control industry to implement dried ham IPM programs. 

Results from this project will benefit the southern dry-cured ham industry in the United States.

Grant Goals and Objectives

The long-term goals of this project are to provide cost-effective and legal methyl bromide

alternative fumigants that can serve as definitive control agents in an IPM program that combines 

sanitation, prevention and monitoring in a decision-making process. New information generated 

from recent work and from that proposed on suppression products and IPM methods in this 

project will be the subjects of one or more educational products such as a training manual or 

website, and that these educational products can also be used in extension programs during and 

soon after this project. Researchers hope to meet these goals by addressing the following six 

objectives in the current project.
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1. Conduct laboratory studies of ham mite mortality or ham protection using sulfuryl 

fluoride at high temperatures, MITC as a new fumigant, and GRAS food additives as ham 

coatings; determine food safety and market quality of hams treated with these 

compounds.

2. Do field validation of phosphine fumigations with cylinderized PH3 and special 

precautions to avoid electrical damage. Conduct at least one commercial fumigation of 

sulfuryl fluoride at a high temperature if results from objective 1 are positive.

3. Sample hams and ham production and aging environments to determine mite density and 

correlate these direct population measurement with capture numbers in mite traps to 

develop predictive models of mite population size based on trap count.

4. Conduct field-scale efficacy trials of food-grade coatings to protect against mites, and 

also of space sprays with registered pesticides to reduce mite populations.

5. Conduct an economic feasibility study and articulate cost-benefit scenarios for IPM and 

related alternatives for the dry cured ham industry.

6. Develop and deliver dry-cured ham IPM programs via educational materials, field 

demonstrations and outreach to industry groups.

4. REGISTRATION UPDATE

No new chemicals have been registered or de-registered since the last nomination. 

5. ECONOMIC INFEASIBILITY OF ALTERNATIVES 

An economic analysis was not conducted because this sector has no technically feasible 

alternatives at this time. 

CITATIONS

Abbar, S., Y Zhao, MW Schilling, and T Phillips. 2013. Chemical Alternatives for Suppressing 

the Ham Mite, Tyrophagus putrescentiae. Annual International Research Conference on 

Methyl Bromide Alternatives and Emissions Reductions, San Diego, CA, Nov.4-6, 2013,

(36).

Amoah, B, MW Schilling, and T Phillips. 2013. Trapping the Ham Mite, Tyrophagus 

putrescentiae, with A Food Bait: Toward A Monitoring Tool for IPM. Annual 

International Research Conference on Methyl Bromide Alternatives and Emissions 

Reductions, San Diego, CA, Nov.4-6, (37).
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 8

Phillips, TW. 2013. Fumigation Alternatives for the Ham Mite, Tyrophagus putrescentiae: 

Challenges and Prospects. Annual International Research Conference on Methyl Bromide 

Alternatives and Emissions Reductions, San Diego, CA, Nov.4-6, 2013, (38).

Zhao, Y., T.W. Phillips, S. Abbar, W.B. Mikel, M.W.Schilling. 2012a. Effects of various foodgrade coatings on mite mortality and sensory quality of dry cured ham. Annual 

International Research Conference on Methyl Bromide Alternatives and Emission 

Reduction, Orlando, FL, November 6-8, (77).
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APPENDIX A

Census of Pork Producers

Repeated from the USACUN2015 for MBTOC’s convenience

In May 2012, Dr. Wes Schilling (Mississippi State University) had 26 country ham producers 

respond to his survey (U.S. Country Ham Facility Survey) concerning use of methyl bromide in 

their facilities. These data provide the size of the aging rooms, the yearly amounts of methyl 

bromide used, and the number of fumigations per year, by facility as requested by MBTOC. 

Facilities use multiple treatments per year because new hams are brought into the aging rooms 

throughout the year and multiple outbreaks may occur. 

The producers monitor the aging rooms for evidence of pests, and when signs of pests are 

present they make the decision to fumigate. Typically they clean and seal the aging room on 

Friday. Gas is introduced after workers leave on Friday afternoon. Aeration usually begins on 

Saturday afternoon. 
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Table 3. U.S. Country Ham Facility Survey Conducted by Dr. Schilling, May 2012

Footnote: These numbers were rounded by Excel spreadsheet after conversion from the original U.S. units. 

The data in Table 3 represent responses by 26 country ham producers. We believe there are 

approximately 28 ham producers in the United States and that the survey therefore represents 

over 90% of the sector. The standard presumption for use in post-harvest treatments is 20 

kg/1000 m3(Handbook on Critical Use Nominations for Methyl Bromide, 2007). Several of the 

facilities listed in Table 3 appear to be conducting fumigations at rates that are higher than the 

standard presumption. Facilities can undertake efforts to maximize their gas tightness and 

thereby aim to bring their use rate to within the standard presumption. The United States 

nomination is calculated by reducing the use rate to 20 kg/1000 m3plus 10% as described by 

MBTOC “a dosage of 20 g/m3, plus a 10% allowance for occasional unforeseen requirement for 

additional MB due to inclement weather or the sudden need for an extra treatment at a particular 

Facility #

Maximum MeBr 

used per year 

(kg)

Aging Room Size 

(1,000 cubic 

meters) 

Maximum 

number of 

fumigations per 

year

MeBr capped 

at 20 kg/1,000 

m3 + 10%

1 55 0.64 4 56

2 272 2.61 5 287

3 91 0.85 4 75

4 681 6.37 4 561

5 55 0.57 4 50

6 50 0.57 4 50

7 45 0.57 4 88

8 64 0.57 4 50

9 272 2.83 4 249

10 1135 7.70 5 847

11 27 0.28 4 25

12 27 0.28 4 25

13 68 0.57 4 50

14 272 2.83 4 249

15 18 0.17 4 15

16 14 0.14 4 12

17 45 0.42 4 37

18 45 0.45 4 40

19 23 0.28 4 88

20 64 0.71 4 62

21 114 1.27 4 112

22 36 0.34 4 30

23 81 0.79 4 70

24 27 0.85 2 35

25 27 0.85 2 35

26 55 1.46 2 41

Total 3,667 35.0 3,240
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facility or possibly for one or two facilities not included in, or responding in time to, the survey, 

summed up as 10% for contingency measures” (MBTOC 2012, pg. 56).
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APPENDIX B

Results Prior to 2013 

Repeated from the USACUN2015 for MBTOC’s convenience

Researchers from Kansas State University and Mississippi State University began investigating

the control of arthropod pests that infest dry cured pork products during the aging process prior 

to the spring of 2007, when a proposal was submitted to the USDA CSREES Integrated 

Research, Education, and Extension Competitive Grants Program- Methyl Bromide Transitions 

by several meat scientists (Schilling and others) and an entomologist (Phillips). This proposal 

was funded from 2007 to 2010. A no-cost extension was granted for 2010-2011, and additional 

funding was provided through the Southern Regions Integrated Pest Management Center to 

continue research efforts for 2010 and 2011. In addition, a grant was submitted to the USDA in 

summer 2011 to seek funds to continue research with respect to potential alternatives to methyl 

bromide for use in the dry cured pork industry. All of the research projects listed above and 

below are being conducted in conjunction with the National Country Ham Association, The 

American Association of Meat Processors, individual ham producers, and the fumigation and 

pest control industries. 

There were several objectives to the research project that was funded by the USDA MBT 

program from 2007-2010. The first was to determine the effectiveness of chemical controls 

(sulfuryl fluoride, phosphine, and methyl bromide) against all life stages of both mold mites 

(Tyrophagus putrescentiae) and red legged ham beetles (Necrobia rufipes). The second 

objective was to determine the effectiveness of carbon dioxide and ozone against all life stages 

of both mold mites and red legged ham beetles. The third objective was to test the effects of 

sulfuryl fluoride, phosphine and methyl bromide on the quality and safety of the dry cured hams. 

The fourth objective was to conduct an economic analysis of the alternatives demonstrated to be 

technically viable alternatives for methyl bromide in this industry. 

Fumigants and Alternatives for Controlling Ham Pests

The results of sulfuryl fluoride efficacy investigations on Tyrophagus putrescentiae, ham mite, 

and Necrobia rufipes, red-legged ham beetle, were presented at the 2008 MBAO Conference, in 

Orlando, FL. The studies included eggs and a mixture of adults and large nymphs of mites and 

the eggs, large larvae, pupae and adults of beetles. The experiments were conducted for 48 hours 

at 23°C at various concentrations of sulfuryl fluoride. The investigators achieved 100% 

mortality of red-legged ham beetle adults and pupae at about 4.0 g/m3, and 100% mortality of 

larvae at 5.7 g/m3. Eggs of red-legged ham beetles died at 24.0 g/m3of sulfuryl fluoride, well 

below the maximum label rate (Phillips et al., 2008). Mortality of ham mites required much 

higher concentrations of sulfuryl fluoride. A concentration of about 100.3 g/m3 was necessary to 

obtain 100% mortality of adults and nymphs under the test conditions. However, this 

concentration obtained only a 95% mortality of mite eggs. This is about three times the legal 

label rate of sulfuryl fluoride (Phillips et al., 2008) and thus indicates that sulfuryl fluoride is not 

a viable alternative to methyl bromide for controlling ham mites. In addition, results also 

indicated that levels of residual fluoride ion and sulfuryl fluoride in the hams were linearly 

related to fumigant concentration and that use of high concentrations of sulfuryl fluoride (72 
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g/m3or greater) and multiple fumigations could potentially lead to high concentrations of 

sulfuryl fluoride and fluoride in the ham (Sekhon et al., 2010a). 

The results of investigations with carbon dioxide, phosphine, methyl bromide and ozone 

treatments on Tyrophagus putrescentiae, ham mite, and Necrobia rufipes, red-legged ham beetle, 

were presented at the 2009 MBAO Conference, in San Diego, CA (Sekhon et al., 2009a, b; 

Phillips, 2009, Phillips et al. 2011, Sekhon et al., 2010b, 2010c). The studies included eggs and 

a mixture of adults and nymphs of mites and eggs, large larvae, pupae and adults of beetles. The 

experiments were conducted for variable times at 23°C at various concentrations of carbon 

dioxide, phosphine, methyl bromide and ozone. The investigators achieved mortality of all life 

stages of mites with a concentration of 60% carbon dioxide with 144 hr of exposure (Sekhon et 

al., 2009a; Phillips, 2009; Sekhon et al., 2010b). However, fumigation with carbon dioxide 

would likely not be applicable since ham structures are not air-tight and 144 hr is too long of a 

time to fumigate the hams. In addition, a carbon dioxide concentration (> 80%) with an 

exposure time of 144 hrs was necessary to cause 100% mortality for all life stages of red legged 

ham beetles (Sekhon, et al. 2009a; Phillips, 2009; Sekhon et al, 2010b). In addition, there may 

be higher numbers of ham mites that can hide in the crevices of the ham that may be able to 

survive during CO2 fumigation. Investigators achieved 100% mortality of all life stages of redlegged ham beetles and ham mites with 48 hours exposure of 400 and 1000 ppm of phosphine, 

respectively (Sekhon, et al. 2009b; Phillips, 2009; Sekhon et al., 2010c). In addition, residual 

phosphine concentrations in dry cured hams that were fumigated for 48 hrs at 1000 ppm were 

below 0.01 ppm, the legal residual limit in stored food products (Sekhon, et al. 2009b; Sekhon et 

al., 2010c), and consumer panelists could not detect differences between control and phosphine 

fumigated samples at 1000 ppm (Sekhon et al. 2009b; Sekhon et al., 2010c). Therefore, 

phosphine can now be considered a potential alternative to methyl bromide for controlling 

arthropod pests of southern dry cured hams. Further testing with a greater number of mites has 

indicated that a greater concentration of phosphine (>1000 ppm) is likely necessary to kill 

substantial mite infestations. In addition, commercial applications of phosphine are planned for 

2010-2011 to determine the efficacy of using phosphine at the plant level. The effectiveness of 

phosphine will be evaluated through the use of both bioassays (with ham present) and on 

hanging hams in a simulated dry cured ham aging room.

Other portions of this research include the economic analysis of using phosphine in comparison 

to methyl bromide, if it is effective at eradicating mites. Commercial applicators and agricultural 

economists are working with us on this portion of the research. Additional items that will be 

researched in the future (if funding is obtained) include the effect of multiple fumigations on the 

sensory quality and residual concentration of phosphine in ham, and the effectiveness of using 

phosphine in dry cured ham facilities. Many processors have indicated that they would be 

willing to help evaluate the efficacy of phosphine (at controlling ham mite infestations) in their 

plant as part of a research project. In addition, we have commitments from Universities and a 

commercial applicator to help implement phosphine fumigation in dry cured ham facilities for 

this research to take place.

Ozone concentrations of greater than 150 ppm for 48 hrs were able to achieve 100% mortality of 

ham beetles and mites at the bench top level (Sekhon et al., 2009b; Phillips, 2009; Sekhon et al., 

2010b). Consumers also could not determine sensory differences between control hams and 
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 14

those that were fumigated with ozone at 175 ppm for 48 hrs (Sekhon et al., 2010b)). However, 

ozone is not able to penetrate surfaces well and therefore may not be effective in real world 

applications since ham mites could potentially penetrate into crevices in the meat and ham 

beetles bore through the meat tissue. Research that was conducted by one dry cured ham 

processor indicated that the use of ozone in a commercial setting was not effective at eradicating 

ham mite infestations, which was likely due to the inability of the ozone to penetrate the surface 

of the ham and the ability of mites to find places to hide where the ozone did not reach. 

However, ozone may have use as part of hurdle technology to help minimize infestations and 

enhance sanitation since it would sanitize areas in the plant as well as equipment that could 

potentially harbor bugs and pathogens.

Further research has recently been conducted on the effects of low pressure and low oxygen 

concentration on the mortality of Tyrophagus putrescentiae (mold mites). Exposure of mites to 

low oxygen with pressure (25 mmHg; approx. 3.0% O2) at 23°C for 144 hrs or greater was 

effective at eradicating more than 95% of each mite life stage (Hasan et al., 2010). However, 

testing with a larger number of mites and under commercial conditions would need to be 

conducted to determine if this technology could be considered a potential alternative to methyl 

bromide. Its limitations include length of application, ability of mites to hide within meat 

crevices, and difficulty in implementing at the commercial plant level.

Food-safe Dips and Coatings to Prevent Mites on Ham

In additional studies (Zhao et al 2012a), ham slices and 1-cm square cubes were dipped directly 

into either mineral oil, propylene glycol, 10% potassium sorbate solution or glycerin for 1 minute 

and dripped on a mesh colander for another minute. Lard was applied directly by rubbing a thin 

layer to cover the whole piece. Ham cubes (2.5 cm ×2.5 cm × 2.5cm) were used for the mite 

infestation study. During the study, 20 mites (mostly adult female) were placed on one cube of 

ham which was placed in a ventilated, mite proof glass container and incubated for 21 days at 

27oC and 70% relative humidity. Mite populations on ham cubes were counted every week. 

Coatings on ham slices were washed off before cooking. Ham slices were oven baked to internal 

temperature of 71 ̊C and served to trained panelists for sensory Difference from Control tests. A 

randomized complete block design with 3 replications was used to determine if differences 

(P<0.05) existed between treatments with respect to mite number and sensory differences 

between products.

Results indicated that both lard and propylene glycol were effective (P<0.05) at controlling mite 

reproduction. No difference was detected in sensory characteristics between control ham slices 

and samples treated with food grade ingredients. In addition, potassium sorbate and mineral oil 

did not inhibit mite reproduction but slowed mite growth (P<0.05) when compared to the 

control, and glycerin was ineffective at lowering mite counts (P>0.05) when compared to the 

control.

The majority of research that has been conducted on use of food grade ingredients with meat 

products has been to prevent water loss and reduce rancidity of meat products (Baldwin, 2007). 

However, a finished ham product needs to lose at least 18% of its original weight during aging 

(USDA, 1999). At the same time, the unique flavors of dry cured ham are caused by proteolysis 
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 15

and lipolysis with the presence of oxygen. In this case, water vapor permeability of the films and 

coatings needs to be considered when choosing a proper coating. Current and future research is 

being conducted to develop a cost-effective food grade coating with high oxygen and water 

vapor permeability. 

Based on the research studies described above (Zhao et al 2012a), the active ingredients that 

show the most promise as potential methyl bromide alternatives are propylene glycol, butylated 

hydroxytoluene (BHT), and lard. Propylene glycol (PG) is likely the most feasible food-grade 

ingredient that could be used to control ham mites but is also very expensive. BHT is effective at 

controlling mites on 1 inch ham pieces at a concentration of 10%. However, 0.01% BHT (by fat 

percentage) is the acceptable level in some meat products. This makes it unlikely that it would be 

accepted for use, but may have application if it can be washed off the surface and there is less 

than 0.01% BHT in the finished product. Lard was effective at controlling mites on ham pieces. 

However, use of lard may prevent moisture loss and transmission of oxygen which would 

prevent the preservation and flavor development of the ham. However, these 3 ingredients need 

to be evaluated on whole hams for their ability to control mite infestations. In December of 

2012, research was started on whole hams such that the hams are treated with BHT, lard, or 

propylene glycol. Hams will be infested with a known number of mites and evaluated over 3 

weeks for the number of mites on the hams. In addition, propylene glycol will be used in foodgrade gel coatings to determine if incorporating PG in a gel will prevent evaporation of the PG 

and prolong its effectiveness at controlling mites. We will also work with processors to 

implement PG and other food grade products that may control mites in their plants to determine 

their impact in industrial settings.

A series of laboratory experiments (Zhao et al 2012a) were conducted in which 1-cm square 

cubes of ham were dipped into a test compound of a given concentration for 1.0 minute and then 

placed in a ventilated glass jar and inoculated with 20 adult mites. Jars were held for 14 days to 

allow for mite reproduction and population growth, after which the total number of mite adults 

and nymphs were counted and compared to numbers produced on other treated ham pieces and 

on control hams dipped in water only. Three groups of experiments were conducted that 

compared common food oils, synthetic polyols and common legal food preservatives. Among 

oils tested, 100% lard from pork fat completely prevented mite reproduction on treated ham 

pieces, while vegetable oils such as olive, corn and soybean had minimal effects on mites. Of 

the polyols, glycerol had little effect on mites while propylene glycol at 100% or 50% prevented 

mite reproduction. Other short-chain diols had significant effects on mite reproduction. Of the 

other food preservatives tested, the various salts of sorbic and propionic acids were effective at 

preventing mite growth when applied as 10% solutions in water. Research so far suggests that 

approved food oils and synthetic food preservatives show potential for protecting dry cured hams 

from mite infestation, and future work will need to address the effects of these additives, if any, 

on the quality of hams during the aging process and on consumer acceptability.

A Simple, Low-cost Trap for Monitoring Ham Mites

Dr. Phillips’ research group (Zhao et al 2012b) developed a mite trap based on the basic design 

of a trap first developed in England. This trap consists of a 90 mm disposable plastic Petri dish 

that is painted black on the entire outer surface. Around the sidewall of the dish are eight evenly 
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 16

spaced holes, approximately 0.5 mm in diameter, at 2 mm above the bottom of the dish for entry 

of responding mites. A food bait was placed inside the middle of the dish and was a 25 mm 

diameter circular plug of mite diet, approximately 10 mm high. Mite diet was composed 

primarily of ground dog food with yeast, glycerin, anti-fungal agent and gelled with 2% agar. 

Mites respond to the baited dishes, enter the holes in the side wall, and feed to the diet plug 

where they mate and lay eggs. Laboratory studies confirmed that traps baited with diet were 

highly attractive to mites compared to unbaited traps. A study was initiated to monitor mite 

populations in which twenty traps were distributed evenly throughout each of three different ham 

production facilities for consecutive one-week periods. Mite numbers lured to traps varied from 

zero to several hundred in one week, and seasonal trapping determined that certain areas of 

facilities had higher mite activity than other areas. Traps confirmed that fumigation in certain 

circumstances caused severe reduction in mite populations, and showed that mites would slowly 

increase activity following fumigation. Future work will attempt to correlate mite trap counts 

with other direct measures of mite density, and also utilize such information to aid in IPM 

decisions. In addition, mite traps will be placed in additional processing facilities to determine 

mite numbers in facilities in different areas in the Southeastern United States both prior to and 

after fumigation.

Simulations of Commercial Ham Fumigations

Three fumigations trials (Zhao et al 2012b) were conducted in 1000-cubic feet shipping 

containers intended to simulate dry cured aging ham houses with phosphine concentrations 

ranging between 1000-2000 ppm and exposure time of 48 hours. Ten dry cured hams were hung 

from racks in each shipping container to simulate dry cured aging conditions. Twenty 

Tyrophagus putrescentiae (ham mites) bioassay jars and ten Necrobia rufipes (red-legged ham 

beetles) jars were placed in each shipping container for each trial. Five of these hams were used 

for mite inoculation and the other 5 hams were used for sensory analysis and phosphine residue 

testing. The lean portion of the dry cured hams (that were used for inoculation) was also 

inoculated with a mixed culture of approximately 1000 mites. Temperature was recorded in the 

ham houses during fumigation.

There were three treatments in each trial: control (no fumigation), low phosphine, and high 

phosphine. Three shipping containers were used during each trial. Phosphine gas was produced 

in the shipping containers using magnesium phosphide cells that reached target fumigation doses 

at between 8 to 12 hours after the fumigation was started. Phosphine concentration was measured 

in the shipping containers using both Dräger tubes and a calibrated UV-VIS detector after 48 

hours fumigation. Average concentration of the three trials after 48 hours fumigation for low 

phosphine treatment (52 grams of magnesium phosphide) was about 1300 ppm. For high 

concentration fumigation treatment (140 grams of magnesium phosphide), average concentration 

was about 1600 ppm. 

The mite mortality was 99.8% in the bioassays at two weeks post fumigation when 2000 ppm 

phosphine was achieved, but not all eggs on either the hams or in the bioassays was controlled, 

even at concentrations as great as 2000 ppm. A lengthier fumigation time was attempted during 

early November, but the ambient temperature was too cold (<15oC) to achieve successful control 

of ham mites. At temperatures of 20oC or greater, all life stages of red-legged ham beetles were 
USA CUN16 POST HARVEST -- Dry, Cured Pork Products Page 17

controlled in all fumigation trials. Variations in test conditions indicated that temperatures and 

exposure time need to be optimized for fumigation since 48 hours was not long enough to control 

ham mites at 2000 ppm and ambient temperatures below 15oC decreased the effectiveness of the 

fumigation against both ham mites and red legged beetles.

Ham slices were oven baked to an internal temperature of 71 ̊C and served to trained panelists. A 

randomized complete block design with three replications was used to determine if trained 

panelists (n=6-8) could detect a difference between fumigated and non-fumigated hams in 

sensory difference from Control Tests. Sensory tests indicated that trained panelists could not 

determine differences (P>0.05) between phosphine treated dry cured hams and non-fumigated 

hams In addition, residual phosphine concentration was below the legal limit of 0.01 ppm in ham 

slices that were taken from phosphine fumigated hams. Further research is underway to 

determine if phosphine can be used at the plant level to control ham mite infestations.

One phosphine fumigation trial (Zhao et al 2012b) was conducted in a 36,000 cubic foot 

processing facility at 1600 ppm. Ham mite assays with live mites were distributed throughout the 

aging room. After 48 hr of fumigation at 1600 ppm (80 F, 70-80% RH), there were no living 

ham mites in the assays. However, phosphine fumigation corroded the electrical switches to the 

fans, and these switches had to be replaced. In addition, the research needs to be repeated when 

many hams are infested with mites to determine if it is effective in real world situations. In 

addition, if phosphine is going to corrode and incapacitate electrical equipment, it will not be 

adaptable to the industry. Sensory panels were conducted to verify that fumigation with 

phosphine did not change the sensory profile of the hams. In this testing, trained panelists could 

not determine differences (P>0.05) between phosphine treated dry cured hams and nonfumigated hams. 

References: 

Abbar, S., M. W. Schilling and T. W. Phillips. 2012. Protecting hams from the mite Tyrophagus 

putrescentiae using food-safe approaches. Annual International Research Conference on 

Methyl Bromide Alternatives and Emission Reduction, Orlando, FL, November 6-8, (44).

Amoah, B., M. W. Schilling, T. W. Phillips. 2012. IPM as an alternative for the ham mite, 

Tyrophagus putrescentiae: monitoring with traps. Annual International Research 

Conference on Methyl Bromide Alternatives and Emission Reduction, Orlando, FL, 

November 6-8, (45).

Hasan, M.M., Phillips, T.W., Aikins, J.M., Schilling, M.W. 2010. Controlled atmosphere 

treatments to control arthropod pests of American dry cured hams. Annual International 

Research Conference on Methyl Bromide Alternatives and Emission Reduction, Orlando, 

FL, November 1-5, (50).

MBTOC, Handbook on Critical Use Nominations for Methyl Bromide, 2007. Available at: 

http://ozone.unep.org/teap/Reports/MBTOC/MBTOC_Handbook_ver_6_Dec_07_final.pdf
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MBTOC. 2012. Report of the UNEP Technology and Economic Assessment Panel. October 

2012. Evaluations of 2012 critical use nominations for methyl bromide and related matters. 

Available at: http://www.unep.org/ozone/teap/Reports/TEAP_Reports/

Phillips, T.W. 2009. Personal Communication.

Phillips, T. W., M. M. Hasan, M. J. Aikins and R, Mahroof. 2011. Fumigation and IPM. 

alternatives for arthropod pests of museums. J. Ent. Acarol. Res. 43: 205-210.

Phillips, T.W. M.M. Hasan, M.J. Aikens, M.W. Schilling. 2008. Efficacy of sulfuryl fluoride to 

control ham mites and red-legged ham beetles. Annual International Research Conference 

on Methyl Bromide Alternatives and Emission Reduction, Orlando, FL, November 11-14, 

(89).

Rentfrow, G., Hanson, D.J., Schilling, M.W., Mikel, W.B. 2008. The use of methyl bromide to 

control insects in country hams in the Southeastern United States. Extension Publication. 

University of Kentucky Extension/National Country Ham Association. Publication # ASC171. Pages 1-2.

Sekhon, R.K., Schilling, T.W., Phillips, Hasan, M.M., Aikins, M.J, Mikel, W.B. 2009.Chemical 

Composition of Dry Cured Hams Fumigated with Carbon Dioxide. Annual International 

Research Conference on Methyl Bromide Alternatives and Emission Reduction, San 

Diego, CA, November 10th-13th, (58)

Sekhon, R.K., Schilling, T.W., Phillips, Hasan, M.M., Aikins, M.J, Mikel, W.B. 2009. Chemical 

composition of dry cured hams fumigated with phosphine. Annual International Research 

Conference on Methyl Bromide Alternatives and Emission Reduction, San Diego, CA, 

November 10-13, (59).

Sekhon, R.K., Schilling, M.W., Phillips, T.W., Hasan, M.M., Aikins, M.J. Mikel, W.B. 2010a. 

Sulfuryl fluoride fumigation effects on the safety, volatile composition, and sensory quality 

of dry cured ham. Meat Science. 84(3):505-511.

Sekhon, R.K., Schilling, M.W., Phillips, T.W., Hasan, M.M., Aikins, M.J., Nannapaneni, R., 

Mikel, W.B. 2010b. Effects of carbon dioxide and ozone treatments on the volatile 

composition and sensory quality of dry cured ham. J. Food Science. 75(5):C452-458.

Sekhon, R.K., Schilling, M.W., Phillips, T.W., Hasan, M.M., Aikins, M.J., Corzo, A. Mikel, 

W.B. 2010c. Effects of phosphine and methyl bromide fumigation on the volatile flavor 

profile and sensory quality of dry cured ham. Meat Science. 86(2):411-417. 

Schilling, W. and T. W. Phillips, 2011. Personal Communication.

Zhao, Y., T.W. Phillips, S. Abbar, W.B. Mikel, M.W.Schilling. 2012a. Effects of various foodgrade coatings on mite mortality and sensory quality of dry cured ham. Annual 
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International Research Conference on Methyl Bromide Alternatives and Emission 

Reduction, Orlando, FL, November 6-8, (77).

Zhao. Y., T.W. Phillips, M.J. Aikins, W.B. Mikel, M. W.Schilling. 2012b. Sensory evaluation 

and pest mortality of dry cured ham fumigated with phosphine in a simulated ham aging 

house. Annual International Research Conference on Methyl Bromide Alternatives and 

Emission Reduction, Orlando, FL, November 6-8, (78).