US CUE16 Replies to MBTOC Final Page 1

NOMINATING PARTY: The United States of America

DATE: MARCH 20, 2014

FILE NAME: USA CUE16 STRAWBERRY FRUIT IN CALIFORNIA 

AND HAM FACILITIES

BRIEF DESCRIPTIVE TITLE: U.S. Response to MBTOC March 6, 2014 Questions on 

Strawberry Fruit and Ham Facilities 

SITE NAME (OPEN FIELD): Strawberry Fruit in California

Dry Cured Meat Products

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

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) 308-7042

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

BACKGROUND

The United States government nomination is for 3,240 kilograms of methyl bromide to fumigate 

aged country hams in 27 facilities and for 231,540 kilograms of methyl bromide to fumigate 

strawberry fruit fields in California. In ham houses, the pest of concern is Tyrophagus 

putrescentiae, the ham mite (also called cheese mite and mold mite), which infests the aging 

hams and renders them unsalable in the United States. No alternatives have yet been identified 

to control this pest under U.S. conditions though research into alternatives continues. In 

California for strawberry fruit this nomination is for areas in California where a transition period 

is needed for the use of broadcast 100% chloropicrin, in fields with high pest pressure, in 
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particular, with Macrophomina and Fusarium or where 1,3-dichloropropene (1,3-D) use is 

limited by township caps. This sector will complete its transition to alternatives by the end of 

2016, in time for the 2017 use-season.

Strawberry Fruit

MBTOC Question 1. The quantity of MB requested for 2015 is 373,660 Kg to treat 2198 ha. 

For 2016, this quantity has been reduced to 231,540 Kg for the treatment of 1,362 ha. What 

alternatives are used on the non nominated area (836 ha). 

U.S. Reply

Primarily 1,3-dichloropropene and chloropicrin or straight chloropicrin at rates up to 392 

kg/ha is used in these transitioned, non-nominated areas. The transition from methyl 

bromide has resulted from extensive work by California strawberry specialists and growers 

to find the most effective rates, application methods, tarps, and other means of managing 

pests formerly managed by methyl bromide. In addition, time was required for developing 

safe and effective procedures to use straight chloropicrin at the recently-allowed higher use 

rates. Non-chemical means (e.g., ASD, steam) as described in the nomination are being 

studied, but not necessarily commercially used at present.

MBTOC Question 2. What does the party mean by “a shift in the production away from 

sensitive sites” Are these sites the full amount of the nomination for 2016 (Appendix 1)? 

U.S. Reply

Sensitive sites include areas near schools, nursing homes, and residential developments 

where due to recent label changes the use of fumigants would require larger buffers, lower 

rates, or additional methods to reduce soil emissions (different tarps or water seals). The 

U.S nomination is for areas where there is a critical need for methyl bromide to treat fields 

1) where a transition period is needed for the use of broadcast 100% chloropicrin in fields 

with high pest pressure, in particular, with Macrophomina and Fusarium and 2) where 1,3-

D is limited by township caps and 3) are not new production areas. Sensitive sites are a 

subset of area where methyl bromide is a critical need. 

Dry Cured Pork

MBTOC Question 1. It is understood by MBTOC that previous research efforts in the US have 

partly focused on determining when and where the mite infestation come from in order to avoid 

their introduction onto the hams. Could you please clarify? 

U.S. Reply

The ham mite is a domesticated pest that has adapted to living on human food in or near 

human habitats and it no longer has a “wild” habitat. In that regard, the ham mite is like the 

German cockroach, house fly, Norway rat and other common cosmopolitan stored-product 

pests. Research by Dr. Phillips at Kansas State University has developed a trap that can 

detect the presence of ham mites and monitor mite numbers over space and time to provide 
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information for pest control decisions. Despite the best efforts to minimize their introduction 

such as sanitation, clearing areas around the ham houses, etc. mites are still found in ham 

facilities.

Regarding the ultimate sources of mites within a ham facility from year to year, they most 

likely are already living in non-treated, or surviving in poorly treated or difficult to treat

areas, or outside of the building. One would hope that early infestation of a new facility is 

rare, but when it does happen the mites were likely brought inside with shipments of food or 

transported on equipment that came from a mite-infested area. Even newly constructed 

facilities have developed problems with mites (see question 6).

MBTOC Question 2. Are the MB treatments of the ham houses sublethal in the first place so 

that surviving mites can attack again or are the mites continually exported from outside? 

U.S. Reply

Methyl bromide treatments are never intended to be sublethal since mites that escape a 

lethal dose of methyl bromide can multiply to be at pest status much faster than mites 

introduced from outside the facility. Facilities take precautions to ensure effective 

fumigations (see question 3); the main source of introduction of mites is from the outside.

New hams are continually introduced into the aging rooms and this process allows for the 

introduction of new mites into the facility. Question 1 addresses the potential sources of 

mite infestations. Current research is developing IPM tools so that ham facilities can 

become less dependent on regular fumigation, and work is also aimed at providing 

effective methyl bromide alternatives that can be used when IPM determines an effective 

fumigation is needed.

MBTOC Question 3. If survivors are the reason, is it possible to modify the treatment and 

possibly the internal construction of the houses? 

U.S. Reply

Ham producers are using the best sealing, fumigation, and IPM processes possible for 

control of mites. The reoccurring mite problem appears to be due to re- introduction (see 

question 1). The best possible fumigation treatment occurs when there are continuous 

improvements to the application of the fumigant, to the structure, and practices of the 

applicators. The building being fumigated must be as gas tight as possible. Permanent 

sealing of certain structural components must be done, and temporary sealing with tape and 

caulk needs to be well-inspected and effectively applied before treatment. All closed 

spaces (e.g., closets, storage cabinets, stairwells, etc.) must be opened to allow gas to 

spread. The temperature should be 21 o C (70o F) or warmer and gas concentrations should 

be remotely monitored at many locations within the building, high and low, so that more 

gas can be added remotely when/if concentrations drop before the treatment ends. U.S. 

dry-cured ham producers make every effort to follow these practices to minimize their need 

for and emissions of methyl bromide.

MBTOC Question 4. Has the party considered additional heat during the fumigation to help 

fully eradicate all present mites and stages? 

U.S. Reply
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The summer or aging room (where the mites are typically found) is typically held at 

approximately 29 o C (85o F) which is generally considered a high temperature for 

fumigations. Further increasing the temperature in the curing or aging rooms will

negatively impact the quality, taste and texture of the ham. Increasing the temperature for a 

short duration (72 hours) during the fumigation process has been shown to be beneficial in 

some situations (e.g. flour mills, food processing plants, etc.). However, it would be very

difficult to heat up the ham facility without increasing the temperature in the curing and 

aging rooms. See description of curing process below. 

Steps in the Curing Process

Step 1 (Winter Room) -- Ham is typically salted and sugared using a dry rub method on 

Day 1 and Day 15. The temperature is approximately 3.3 o C (38 o F) with low humidity. 

Sometime between days 42 - 50, the salt and sugar are scraped and rubbed off of the ham. 

The hams are then moved to the spring room. In this room, the high salt content and low 

temperature is sufficient to keep insect pest pressure to a minimum. 

Step 2 (Spring Room) -- After being removed from the winter room, the hams are 

wrapped in cotton netting and placed in the spring room for only 10 -15 days before being 

moved to the summer room. The temperature is approximately 10 - 13o C (50 - 55 o F) at 

50% humidity. The humidity is very important at this stage and it is monitored closely. 

Most hams are equalized in the spring room. Equalization is a process whereby the salt 

cure penetrates from the surface of the ham, through the skin, and to the inner portion of 

the ham. There are no insect problems here due to the low temperature and the limited 

amount of time that the hams are in this room.

Step 3 (Summer or Aging Room) – Hams are next moved to the summer (or aging room) 

for up to 18 to 24 months. The temperature is maintained between 27 - 32 o C (80 - 90 o F)

at 55% humidity. These conditions are very important to develop an intense, concentrated 

flavor and aroma. As the ham ages, the moisture content of the ham will decrease, the salt 

content increases, and the chances of bacterial action become limited. If desired, smoking 

of the hams may occur here, or in a separate “smoke house”. Since the temperature and 

humidity are higher in this room, conditions are ideal for pest pressure. It is at this stage 

that the application of methyl bromide is necessary.

MBTOC Question 5. Has a HACCP program been considered/implemented to avoid 

reinfestation of the hams?

U.S. Reply

The research discussed in question 1 was designed in part to better understand how mites 

are introduced into ham facilities. We plan to use the results of this and other research to 

implement a mite IPM plan as part of the Hazard Analysis Critical Control Point (HACCP) 

program. HACCP is a systematic preventive approach to food safety required in certain 

U.S. food industries. HACCP plans look at every possible process and location in a food 

plant that could allow entry of pathogens or otherwise cause unsafe food or loss or spoilage 

of food, identify the critical points (place and/or time) in the process that a set-back can 
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occur, and instil special monitoring or inspection at the critical point so that problems can 

be avoided or readily corrected. 

For prevention or resolution of ham mite problems, the USDA-funded research in Kansas 

and Mississippi aims to develop an integrated pest management, IPM, program specific for 

the ham mite that can be incorporated into the HACCP plan. IPM programs are like 

HACCP programs, but HACCP is generally broader in its application to both food safety 

and pest management. Mite IPM that are currently used involve thorough sanitation to 

remove existing mite infestations and food debris that can support mites, regular cleaning 

of floors and shelves to reduce mites, possible application of residual pesticide sprays on 

floors, walls and other surfaces to kill mites walking across them, monitoring mite 

populations with traps, as well as monitoring temperature, lighting and relative humidity 

for conditions that are conducive to mites. When traps indicate that mites have reached an 

action threshold then fumigation must be done effectively. The IPM monitoring and 

sanitation can help to develop a pest HACCP plan for each facility that may include high 

risk areas needing regular cleaning or certain rooms over others that tend to have more mite 

problems. The goal of the USDA supported research is to develop a sound IPM program 

with effective eradication tools (e.g. fumigation with methyl bromide alternatives) so that 

mites are kept well below the action threshold. 

MBTOC Question 6. Has the party considered the construction of new ham houses that are 

modified so that mite infestation can be reduced and fumigation efficacy improved? Potentially 

control may be possible with the use of single isolated compartments that are used like 

quarantine compartments in the same plant. Is this possible and/or has it been considered? 

U.S. Reply

Unfortunately, even the construction of a new plant or the use of separate storage rooms 

has not prevented mite infestations. One new facility opened in 2008 in Kentucky suffered 

ham mite outbreaks the first year even when no old hams were moved into the facility. That 

particular facility has wall surfaces which are all washable, is securely sealed, has concrete 

floors, and does not have trees around the new facility, all of which were not sufficient to 

eliminate mite outbreaks. However, the number of methyl bromide fumigations per year 

has decreased from four to two and are applied only when mites are observed. Another 

company in Virginia with separate storage rooms has seen no difference in infestation 

rates. 

MBTOC Question 7. The US has previously presented to MBTOC the potential for protecting 

the ham pieces by enveloping them with mite proof enclosure like fine gauze. Has this technique 

progressed or been considered commercially? 

U.S. Reply

Various studies have demonstrated that fine mesh metal or nylon screening with openings 

less than 0.066 mm, but preferably less than 0.053 mm, can exclude most to all mobile life 

stages of the ham mite, though a trial using such screens on dried hams to prevent mite 

infestation has been planned but not yet undertaken. Recent funding from USDA will 

allow the Kansas group to test the potential for fine mesh screen to prevent mite infestation 

of clean ham pieces. 
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However, even if an effective screening system is shown to be physically possible to 

protect individual hams, the application of such a practice commercially will require

additional process steps to be tested (e.g., wrapping the ham, hanging without damaging the 

mesh, and the process of mesh removal without damaging the ham). In addition to the cost 

of the mesh material, there are unknown additional processing costs and the possibility of

unforeseen sanitation problems. Mite IPM and disinfestation would still need to be 

practiced in all facilities to manage mites that are not directly on aging hams but rather on 

food debris or other spaces. Future research will investigate such issues.

MBTOC Question 8. The CUN also mentioned that Phosphine tested in the laboratory was 

effective against all stages of mites within the label rates of the fumigant and dried meats are 

already listed on the application label (page 5). Magnesium Phosphide was chosen over 

Aluminium Phosphide because it produces twice as much hydrogen phosphide but corrosion in 

electrical switches of fans, wirings and equipment in the holding areas was present 21 days after 

fumigation. Future work needs to be done to address the corrosion problem (page 6).

U.S. Reply

Yes, initial work on ham mite control determined that phosphine gas, hydrogen phosphide 

applied at 25o C is very effective at controlling all stages of ham mites well within label 

application rates. However, phosphine gas by itself is corrosive to metals like copper, 

silver, and gold, and the so-called metallic salt solid formulations that have ammonium 

compounds generated along with phosphine are more corrosive than pure phosphine due to 

the ammonium compounds. The high temperature and relative humidity in the summer 

room are also potentially conducive to increased rates of corrosion. Techniques to protect 

structures from corrosion, as well as efficacy of non-corrosive fumigants as alternatives to 

both phosphine and MB, are being researched now under the current USDA project in 

Kansas and Mississippi. See question 9 for future planned work.

MBTOC Question 9. What is your future plan to prepare ham production facilities for the 

corrosion potential of phosphine gas? 

U.S. Reply

While the scientists in the Kansas-Mississippi collaboration are not experts in chemicalcaused corrosion, discussions with fumigators experienced in phosphine and corrosion 

prevention suggest a course of action. Of the various formulations of phosphine available,

the cylinder-based gases should be the least corrosive. Thus either ECO2FumeTM, which is 

less than 2% phosphine with 98+% carbon dioxide, or VaporPhosTM, that quickly releases

99% phosphine and rapidly blends it with air, will be used in trials at ham facilities. 

Cylinder-based phosphine lacks the corrosive ammoniums and also can be quickly applied 

to the target concentration, and adjusted throughout the course of a fumigation to maintain 

desired doses. Additionally and very importantly, the building will be a carefully inspected 

by the experienced fumigators to locate all potential corrosion sites and then protect these 

from phosphine gas. Numerous techniques, such as bagging and positive-ventilating 

machines or protecting sensitive spaces with CO2, or coating electrical junctions with oils 

or other gas-impermeable materials, will be used. The university researchers will work 

closely with special fumigators to carefully evaluate corrosion prevention and insecticidal 

improvements. A long-term goal is to consult with industrial engineers and construction 
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experts on ways to re-engineer ham facilities to isolate sensitive metal fixtures from the 

fumigated spaces and to also provide guidance for new construction to be phosphine-safe.

MBTOC Question 10. Similarly, has magnesium phosphide, which has proven to be effective 

in controlling all stages of mites, been considered for use in the aging rooms where electrical 

switches to the fans subjected to corrosion could be covered/protected? 

U.S. Reply

As per question 8 and 9 above the U.S. researchers recommend that no metallic phosphide 

formulations be used in any ham facility, and if phosphine is chosen over other fumigants 

that guidelines developed for corrosion protection be used.

MBTOC Question 11. In view of the research findings reported in the CUN, has the party 

considered a transition plan for this sector and what is it? 

U.S. Reply

The United States country ham producers continue to look for technically and economically 

feasible alternatives for the control of mites. In addition to the research just cited, please 

refer to the Critical Use Nomination for our research on non-fumigant chemicals to control 

ham mites. While significant progress has been made, to date, such an alternative has not yet

been identified but we remain committed to continue our research efforts to find such 

alternatives and to minimize emissions of and the need for methyl bromide.