STATE PLANT BOARD
September 1943 E-601
UITED STATES DEPARTMENT OF AGRICULTURE
Agricultural Research Administration
Bureau of Entomology and Plant Zuarantine
METHYL BROMIDE FUMIGATION
Prepared in the Division of Control Investigations
Introduction ................ ...... .. ...... .... 1
Uses of methyl bromide ............................. 1-2
Properties of methyl bromide ....................... 3
Detection of the gas ............................... 3-4
Protection to operator ...........................* 4-5
Types of fumigation chambers ....................... 6-7
Dosage schedules ... .*....*.*.*. ............ ... ;* 7-8
Method of applying dosages ......................... 8
Calculation of dosage ..........e...............***. 9
Effect of humidity .............................. ... 9
Circulation and venting ........................... 9-10
Plant reaction ......*.......... e............... 10-11
The use of methyl bromide as a fumigant is relatively
recent, and many requests have come to the Bureau for informa-
tion concerning it. The following information has been assem-
bled in order to acquaint those interested with its general
characteristics and uses.
Uses of Methyl Bromide
Methyl bromide has been found effective against a wide
variety of insects, as well as red spiders and other mites,
and against all stages. It has properties of penetration
which make possible the destruction of certain sheltered pests
such as leaf miners, borers, mites, and other internal feeders.
In common with certain other fumigants, its lethal action is
delayed for a time following fumigation. This period may be
several days with some species, and will vary according to the
excess above the minimum lethal dosage.
The uses of methyl bromide have increased rapidly in the
last 5 years, as more and more entomologists have utilized it
in the solving of their insect-control problems. In its gaseous
state its employment is usually limited to fumigation in tight
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It has been widely applied for the fumigation of plant
material to allow movement from within quarantined areas. Its
use is authorized under Federal or State regulations for the treat-
ment of most imported plant material for propagation, as well as
for imported green pod vegetables, cipollini bulbs, and chestnuts;
for domestic nursery and greenhouse plants, and shipments of fresh
vegetables and fruits for certification under the Japanese beetle
quarantine; for nursery hosts of the oriental fruit moth and the
white-fringed beetle; for azaleas infested with the azalea leaf
roller; and for hosts of the camellia scale. It also has been
authorized for the fumigation of the potato tuber moth in white
potatoes, the sweetpotato weevil in sweetpotatoes and sweetpotato
draws and vine cuttings, the strawberry crown borer in strawberry
plants, Hypera brunneipennis in baled hay, host plants of the
European corn borer and the citrus whiteflies, carriers of the pear
psylla, the grape phylloxera on grapevines, Christmas trees for cer-
tification under the gypsy moth quarantine, narcissus bulbs from
certain producing areas, and probably others.
In commercial insect control it is used in many ways: For
greenhouse plants, especially those infested with cyclamen and
other related mites; for various coccids on potted plants; for
the codling moth in pears; for the tomato pinworm; and for the
gladiolus thrips on corms. It is also used for storage-infest-
ing insects in milled flour and feeds, and in seeds, and for
their control in rice and wheat mills, seed houses, and candy
manufacturing plants. Other uses include the fumigation of
dried fruits, nut meats, dry beans and peas, green coffee beans,
nocea antiques, chicory, spices, chestnuts, macaroni products,
dehydrated soups and vegetables, cocoa and chocolate, dairy pro-
ducts including cheese, dried milk, and butter, and margarine.
Methyl bromide is mixed with ethylene dichloride and car-
bon tetrachloride as a fumigant for stored grains, and with hy-
drocyanic acid for certain treatments applied by private commercial
Methyl bromide is also used as a soil fumigant by injection
as a liquid, but it is injurious to plant life when used in this
miLnner. It has been authorized for the treatment of potting soil
and soil plots or plunging beds under the white-fringed beetle
quarantine. It has also been widely used for control of colonies
of t he Texas leaf-cutting ant by injection into the colony
entrances. It can also be diluted with water and used as a soil
fumigant in quarantine treatments against the Japanese beetle and
the white-fringed beetle.
Properties of Methyl Bromide
Methyl bromide (CH Br) is a colorless, odorless, volatile
liquid, with a specific gravity of 1.732 at O C., and a boiling
point of 40.1 F. It is a gas at ordinary temperatures, in
which state it is approximately 3.3 times as heavy as air. It
is soluble in most common organic solvents but is only slightly
soluble in water. It has been used as a fire extinguisher.
It is normally procurable in 10-, 50-, and 150-pound cy-
linders, or in 1-pound cans. It is obtainable from the follow-
ing manufacturers :/
The Dow Chemical Company, Midland, Mich.
E. I. duPont de Nemours & Company, Wilmington, Del.
Michigan Chemical Corporation, St. Louis, Mich.
Pittsberg Chemical Company, Vernon, Calif.
Methyl bromide will soon be obtainable in glass ampules
of various sizes. The names of possible sources from which
these may be purchased will be given upon request.
Detection of the Gas
A halide detector, several types of which are marketed
by refrigeration supply companies as refrigerant leak detectors,
is the easiest and most useful means of determining the presence
or absence of harmful concentrations of methyl bromide gas. The
detector consists of an alcohol or acetylene torch which heats a
copper cone or tube, and an air tube or hose through which the
air to be tested is passed over the copper. This tube facili-
tates drawing samples from between or within containers. A green
flame is produced when fumes of a halide pass over red-hot copper.
Best results have been obtained with the alcohol torch type.
After the torch is lighted it should be allowed to burn un-
til the copper cone or tube glows at red heat and a blue inner
flame shows above the copper. The valve can then be regulated
until the blue flame just disappears beneath the end of the cop-
per cone or tube when viewed horizontally.
/ The accompanying list of concerns and their products
is included for the information of the users of this circular
without any given or implied guarantee of the reliability of the
firms or endorsement of their individual products. No attempt
has been made to make the list fully complete, and no discrimina-
tion is intended or implied against firms whose names or products
are not listed.
- 4 -
When the sampling tube is placed in air containing methyl
bromide a green or blue flame will be seen in the torch, depend-
ing on the concentration. The following tabulation, prepared by
one of the manufacturers of methyl bromide, gives the approximate
methyl bromide concentration associated with color intensity in
Parts CH Br
per million, Pounds CH 3Br
by volume- per 1,000 cubIc feet Flame color
0 0 Almost invisible
40 0.010 Rather faint green
60 .014 Moderate green
100 .024 Moderate green
130 .031 Strong green;
slightly blue at
180 .043 Strong green; rather
240 .058 Strong blue-green
360 .086 Strong blue-green
800 .192 Strong blue
The detector should be cleaned before each use, as lint
often lodges in the throat. The cone in the alcohol torch will
become red hot only when the flame is strong and direct through
the center of the cone. If the flame spreads around the cone,
it will not heat properly and often a green color will show in
the absence of any halide. In the latter event the lamp should
be cooled and cleaned and another attempt made.
Protection to Operator
Since methyl bromide is injurious to all forms of animal
life, proper caution should be observed when hj ang it. .on-
tinued exposure t low concentrations l o o e ubjAi-
ed. An operator should use an proved a mak when exposed to
the gas at fumigation concentrations. The mask should b
e-quipped-with a black canister, e B, for organic vapors, as
Erov ed by th ueau of Mines as .per schedule 14D or12&. The
-&nufacturer' s instructions on c aster should lowed
rigidly. Do not use a mask in known concentrations ronger
than the lIl-stat ed on the canister, nor for total osure
p-eroTs--onger than those recommended. Canisters can be pro-
curd from the folloig-firms (see footnote 1, page 3):
Mine Safety Appliance Co. AB CMA
E. D. Bullard Company CM CM-1
Davis Emergency Equipment Co. M-1 C-I
Considerable information is available on the effect of
methyl bromide gas on warm-blooded animals.2/ It has been shown
that they can survive high concentrations for brief periods,
but that prolonged exposures to low concentrations may be injur-
ious or perhaps lethal. From these studies it is considered
that momentary exposure of operators to fumigation concentra-
tions by accident, as might result from opening a vault door be-
fore venting and thus being subjected to a few seconds of
exposure, is not likely to cause injury, but working many hours
in a low concentration may be harmful. It is indicated in the
studies on animals that prolonged and repeated exposures to con-
centrations as low as 33 PPM can be injurious.
Two effects are produced, (1) a paralysis, resulting from
continued exposure to low concentrations, from which animals can
completely recover when removed from the environment 6f the gas,
and (2) with higher concentrations, lung irritation which can
become severe and acute, often developing into typical confluent
The effects are additive during a given exposure period
or in closely repeated exposures, but where exposures are irregu-
lar and at intervals of several days the effects can apparently
be thrown off by the body.
Liquid methyl bromide when spilled on the skin will some-
times cause burning on certain persons. It has been observed
tnat a few individuals become sensitive to methyl bromide and
are easily burned by contact with it in liquid form. Burns on
the feet of men applying quantities of liquid methyl bromide as
a soil fumigant have also been reported. It is inadvisable for
any except experienced technical personnel to attempt to handle
liquid methyl bromide.
2/ Irish, D. D., Adams, E. M., Spencer, H. C., and Rowe,
V. K. 1940. The response attending exposure of laboratory
animals to vapors of methyl bromide. Jour. Indus. Hyg. and
Toxicol. 22(6): 218-230.
Sayers, E. R., Yant, W. P., Thomas, B. G. H., and Berger,
L. B. 1929. Physiological response attending exposure to vapors
of methyl bromide, methyl chloride, ethyl bromide, and ethyl
chloride. U. S. Pub. Health Serv. Bul. 185. 56 pp.
Types of Fumigation Chambers
Successful methyl bromide fumigation can be done in
almost any tight enclosure, such as fumigation vaults, convert-
ed drums, tents or tarpaulins, storage rooms, van or refrigerator
trucks, and refrigerator or freight cars. Conditions associated
with various materials to be fumigated limit the use of certain
of these. In general, fumigation to meet quarantine requirements
must either be done in a standard enclosure (usually a metal-
lined vault) or the dosage schedules must be increased to compen-
sate for probable leakage. For commercial insect control, dosage
schedules can be developed for the specific enclosure used.
For atmospheric vault fumigation, the best type of vault
is longer than wide and is provided with a blower to be used for
circulation and for venting. In this arrangement, as shown in
figure 1, the blower is mounted on the back wall next to the ceil-
ing, directing the air flow along the ceiling toward the front.
For venting, a trap door is dropped in front of the blower, thus
directing its discharge to the outside, and at the same time fresh
air is admitted, either through a small intake or by slightly open-
ing the front door.
For most uniform results th. vault should be lined with
sheet metal, but good results are also obtained with plywood or
pressed wood linings. All joints should be soldered or sealed
with a nonhardening bituminous compound (caulking compound). The
whole end may serve as a door, as shown in figure 1, or in small
installations the side can be used as the door. The'door should
be clamped against two parallel strips of molded sponge-rubber
gasket. All other openings should be similarly gasketed.
If temperature control is desired, the vault can be made
self contained by adding thermostatically controlled electric
heaters. The walls can be insulated or not, as desired. Plans
are available upon request.
Methyl bromide can be used satisfactorily in equipment for
A small type of fumigation chamber can be made from a steel
drum by providing a water-sealed lid. Plans of this unit are
available upon request. Drums, tight boxlike hoods, wooden
barrels, or cylinders can also be used by inverting them over
objects to be fumigated.
Tent or tarpaulin fumigation can be performed by using
cloth coated with ethyl cellulose, vinyl resin, or other similar
coating materials. Ordinary canvas duck tarpaulins apparently
do not retain methyl bromide sufficiently well to insure satisfac-
tory fumigation. Refrigerated freight cars and trucks make good
fumigation chambers. Other enclosures that would normally be
too leaky, such as freight cars, van trucks, and rooms, can be
made usable by sealing all cracks with masking tape, a product
sold by automobile supply companies, or with flour-oil paste.
Dosage schedules for methyl bromide fumigation are com-
posed of three elements, each equally important: (1) Amount of
methyl bromide, (2) exposure period, and (3) temperature. It
has been found that generally one-half pound of methyl bromide
and one-half hour of exposure have about the same value, so
that any modification of a dosage schedule can be either in dos-
age or in exposure in those proportions. Methyl bromide is more
effective at higher than at lower temperatures, and the change
in effectiveness is at a fairly constant rate for any given in-
sect or environment. Available data indicate that a 50 to 100
change in temperature is equivalent to one-half hour of exposure
or one-half pound of dosage. This ratio of course changes as
the schedules approach dosages of less than 1 pound, exposures
of less than 1 hour, or extreme temperatures.
This fairly constant rate of change has made it possible
to establish series of dosage schedules ranging from low to high
temperatures all of which have arprcimately the same effective-
ness on a given irsect and the same degree of tolerance from the
plant host. In instances where the schedules are near the min-
imum lethal amount, the series have small temperature differences.
Where the schedules of a series are considerably over the minimum,
they are fewer with greater temperature differences.
Fumigation schedules developed to date are too numerous to
be discussed here. At 70 F. the minimum schedules for accessible
insects appear to be about 2.5 pounds for 1.5 hours (or 2 pounds
for 2 hours).
A moderate dosare schedule sufficient for most insects and
well tolerated by most plants is 3 pounds for 2 hours at 70.
For some insects imbedded in vegetables, fruits, and nuts
it is sometimes necessary to use dosages of 4 to 5 pounds for 3
to 5 hours, but many succumb to 2 pounds for 2 hours at 70.
Insect larvae in soil balls on nursery plants require 1.5
pounds for 2.5 hours at 73 for the Japanese beetle and 3.5
pounds for 1.5 hours at 70 in vacuum for the white-fringed
For the fumigation of grain or inert materials, a schedule
of 1 pound for 24 hours at prevailing temperatures is generally
Successful fumigation has been done with methyl bromide
from 00 to 95 F.
Method of Applying Dosages
The dosage of methyl bromide is released within the cham-
ber through a closed system from the outside. It can be released
either by spraying through an ordinary spray nozzle into the air
stream in front of the blower, by allowing it to evaporate from
a shallow pan, or by volatilizing it through a heated coil.
"'here the calculated dosage of methyl bromide is 1 pound
or more it can be measured by weight. To do this, the cylinder
of methyl bromide is placed on platform scales and accurately
weighed. The desired amount is then subtracted from the total
and the scales are set at that point. The gas is slowly released,
and when the weight bar again balances the valve is closed. In
this case the cylinder of gas is connected directly with the fum-
igation vault by light copper or plastic tubing. Near the cylin-
der the tubing should be arranged in a spiral coil of two or
three turns to reduce to a minimum its influence on the weight
of the cylinder.
Special glass measures, or dispensers, have been'devised
to measure small quantities of methyl bromide. One type is in-
se'ted in the line between the supply cylinder and the vault.
By use of valves the desired amount is admitted to the measure,
which is graduated in cubic centimeters. The methyl bromide re-
mains as a liquid in the measure, since it is still under
pressure. To release, valves on the other side are opened, and
its own pressure forces the dosage into the vault.
Another type of dispenser holds the contents of a 1-pound
can and the dosage is removed by subtraction. A third type
delivers the entire contents of a can into the vault and is use-
ful where the amount of fumigant desired is in multiples of 1
These dispensers can be procured from the Arrow Products
Company, Carlstadt, N. J.j the Dow Chemical Company, Midland,
Uich., or Bobbink and Atkins, East Rutherford, N. J. (See foot-
note I on page 3.)
Calculation of Dosage
When a dosage of methyl bromide is calculated by weight
the following formula is used:
Divide the volume of the vault in cubic feet by
1,000, then multiply this quotient by the dosage
rate as expressed in pounds per 1,000 cubic feet.
(Example, for a dosage of 2.5 pounds per 1,000
cubic feet in a 1,400-cubic-foot vault it would
take 00 x 2.5 a 3.5 pounds.)
When a dosage of methyl bromide is to be measured the
following formula is used:
Multiply the index of the desired rate (see below)
by the capacity of the vault in cubic feet.
(Example, for a dosage of 2 pounds per 1,000 cubic
feet in a 31-cubic-foot vault, 0.52 x 31 = 16.12
cc.) (The basic index is 0.26 cc. per cubic foot
per pound per 1000 cubic feet.F
Rate per 1,000 cubic feet Index
1 pound 0.26 cc. per cubic foot
1.5 pounds 0.39 cc. per cubic foot
2 pounds 0.52 cc. per cubic foot
2.5 pounds 0.65 cc. per cubic foot
3 pounds 0.78 cc. per cubic foot
3.5 pounds 0.91 cc. per cubic foot
4 pounds 1.04 cc. per cubic foot
Effect of Humidity
The efficiency of methyl bromide apparently is not im-
paired by the presence of moisture; in fact, better results are
often obtained under conditions of high humidity. Enough water
to form a protective film, however, will sometimes reduce the
Circulation and Venting
Methyl bromide gas will stratify if no circulation is
provided in the fumigation chamber, and an overdosage or length-
ened exposure is necessary to offset that condition.
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If fumigation is done at prevailing temperatures, a short
period of circulation during and following the application of
methyl bromide is sufficient to mix the gas and air thoroughly.
If temperature control is necessary, circulation should continue
for the duration of the exposure, since heat stratification will
occur otherwise. If rapid penetration is desired in a short ex-
posure period, continuous circulation will probably be desirable.
The fumigation chamber should not be entered, except by
men wearing gas masks, until the gas in the free air spaces has
been exhausted through the venting system. This can be determined
with the halide test lamp. Gas will continue to be present in the
containers or load for a period of 1 hour or more but it is gen-
erally safe to handle such material if the exhausting continues,
as this will keep a drift of fresh air moving toward the rear of
In general, living plant material is unaffected by or-
dinary dosages of methyl bromide, although any plant can be in-
jured by overdosages or careless attention to details. In the
fumigation of living plants the directions as to dosage, temper-
ature, and length of exposure should be followed rigidly.
Dormant plant material is more tolerant than growing
plants. Nonfoliated dormant material (deciduous woody plants,
bulbs, corms, roots, tubers, etc.) is more generally tolerant
than foliated dormant plants. There are some plants that are
injured consistently by moderate dosages, such as a few azaleas,
certain coniferous evergreens in a partially dormant or nondor-
mant state, a scattering of perennials, and a few potted green-
house varieties, particularly rooted chrysanthemum cuttings.
The list of plant varieties successfully fumigated runs into the
Vegetable produce generally has been uninjured in experi-
mental and commercial treatments to date. Potatoes, sweet-
potatoes, tomatoes, onions, cabbage, snap beans, lima beans,
pigeon peas, turnips, sweet corn, carrots, and beets all have
been fumigated in carload lots. Eggplant and peppers are consid-
ered to be easily injured but have been fumigated successfully
in mixed carlots. Cauliflower, celery, honeydew melons, canta-
loupes, papayas, pod peas, bunch radishes, and dried garlic
have been fumigated experimentally without injury. Cucumbers,
however, have been consistently injured.
Apples, peaches, and pears have been fumigated in car-
load lots, and apricots, cherries, grapes, and plums have been
The same species or varieties of plants often react dif-
ferently under different conditions. Therefore, wherever pos-
sible, trial tests should be made prior to the fumigation of
plant materials or produce in any quantity, or where new instal-
lations, new conditions, or new plant varieties are involved.
This is most important in regard to potted greenhouse plants.
Since methyl bromide is known to be injurious to humans,
persons not familiar with handling fumigants are cautioned
against using it until they have thoroughly familiarized them-
selves with the necessary precautions.
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