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INSECT PESTS

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^ f;^ AGRICULTURE HANDBOOK NO. 129

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Agricultural Marketing Service ^^^

U.S. Department of Agriculture/Washington, D.C.

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Restangular vacuum vault loaded with rice ready for fumigation.

Climatic conditions prevailing in the Gulf States and in

California where rice is grown favor the rapid increase of

insect pests in the rice after it is placed in storage. Strict

sanitation on the farm, in elevators, warehouses, and mills,

and the storage of rough and milled rice in structures that

are tight enough for fumigation can do much to prevent

serious losses from insect attack.

The bulletin discusses the use of methyl bromide, hydrocyanic acid, ethylene oxide, and other fumigants found

effective in treating stored rice. New and more efficient

methods of fumigating rice are described.

This handbook replaces Farmers'' Bulletin No. 1906,

Insect Pests of Stored Rice and Their Control.

Washington, I). C. Octoher 1957
CONTROLLING INSECT PESTS OF STORED RICE

Prepared by Stored-Product Insects Section, Biological Sciences Branch, Marketing Research

Division, Agricultural Marketing Service, U. S. Department of Agriculture

Contents

Page

Insects infesting rough rice 4

Insects infesting milled rice 6

Sources of infestation 7

Good housekeeping 7

Sanitation on the farm 8

Sanitation in the elevator 8

Sanitation in the warehouse__ 8

Use of aerosols and space

sprays 9

Treatment of rough rice 9

Fumigating rough rice in bins- 9

Control of surface infestation

of moths 10

Forced circulation method of

rough rice fumigations 11

Heating and drying rice 13

Eice is produced commercially

on a large scale in the United

States principally in Louisiana,

Texas, Arkansas, Mississippi, and

California. The average production of rough rice for the 10 years

1942 to 1951 in these states was

35,120,000 hundred-pound bags. In

1955 it was 53,420,000 bags.

Annual losses caused by insects

that attack rice in storage are estimated to be about 1 percent of the

total value of the crop. This does

not take into consideration the cost

of prevention and control of insect

infestations or any injury which the

reputation of a milling company

may suffer if its well-established

Treatment of rough rice—Con.

Synergized pyrethrum protective dusts and sprays 13

Insect control in the rice mill 14

Treatment of tailings from

cleaning machinery 15

Treatment of milled rice

Warehouse fumigation 16

Atmospheric-vault fumigation

of milled rice 21

Vacuum fumigation 24

Fumigation of rice in railway

boxcars 25

Fumigation of rice under gastight sheets 27

Precautions in the use of

fumigants 29

brands of products are found to be

contaminated by the presence of

insects.

Rice is for the most part harvested with the combine. In the

Gulf States, it is harvested when

the moisture content is about 22 percent, so that artificial drying is

necessary before it can be stored

safely.

Rough rice is stored in sacks in

warehouses or in bulk in farm bins,

elevators, or in flat storages. Warehouses used for storing sacked

rough rice are often simple, loose

construction, many of them of the

frame and sheet-metal type shown

in fixtures 1 and 2.

1
Figure 1.—Warehouse used for storing rougli rice. This building is 300 feel long

and 180 feet wide and has a storage capacity of 20 million povinds of rice.

They vary in storage capacity

from a few thousand to more than

a million bags in the blimp hangar

shown in figure 3.

Warehouses used for storing

rough rice are now being built with

well-fitted, sheet-metal walls and

may be of the quonset type or the

conventional warehouse construction. Many of them are equipped

for aerating the rice (fig. 4).

Elevators used for storing bulk

rice are sometimes of the crib type

(fig. 5), although modern concrete

elevators are available for storage

in many areas.

The rough rice is sold to the miller, who may transfer it to the mill

immediately, or leave it in the producer's warehouse or elevator until

he is ready to move it. The rice is

milled as rapidly as practicable,

Figure 2.—Interior view of warehouse shown in figure 1, showing method of

stacking rough rice. The concrete floor simplifies cleaning operations.
Figure 3.—Blimp base at Hitchcock, Tex., being used to store 1,200,000 cwt. of

rice. The building is 1,000 feet long, 300 feet wide, and 190 feet high.

(Courtesy H. T. McGiU.)

and the milled rice stored in bulk in

bins, or in burlap sacks, commonly

called pockets, each weighing 100

pounds. Much of the milled rice is

stored in the mills and may be reconditioned before it is shipped.

Large stocks of rice acquired by

the Government in payment of

loans are stored in warehouses as

both milled and rough rice.

Milled rice is wholesaled in 100-

pound burlap or cotton sacks, and

sometimes in paper bags, which are

enclosed in cotton bags. For retail

sale it may be packaged in small

cardboard cartons with or without

cellophane windows, in heavy paper

bags, or in cellophane bags.

Most of the packaged rice is

packed shortly before it is shipped,

and is shipped in corrugated-paper

shipping cases.

The climate in much of the area

in which the rice is produced and

stored is highly favorable for the

multiplication of insect pests of

stored rice. The warm season is

long, the winters are mild, and conditions seldom become too dry in

the gulf region to interfere with

insect activity. Many of the warehouses and mills used are not tight

enough for successful mass fumigation with gas, nor are they equipped

to store the infested and uninfested

rice separately. Some rice mills

carry rough and milled rice in the

same building, providing opportunity for the insects to migrate
Figure 4.—Quonset type warehouse

equipped with floor ducts and fan for

aerating rice.

from one lot to tlie other. A few

mills are equipped with atmospheric

or vacuum vaults in which milled

rice is fumigated just prior to being

shippeH.

Some 30 species of insects have

been found infesting stored rice and

rice products, but only a few of

these are a serious menace to rice

in good condition. Only the more

important insects are considered in

this bulletin. For brief accounts

of the life histories and habits of

the insects that infest rice and other

stored grains, together with illustrations of tlie more destructive

forms, the reader is referred to

Farmers' Bulletin No. 1260, StoredGrain Pests, issued by the TTnited

States Department of Agriculture.

INSECTS INFESTING ROUGH RICE

The lesser grain borer (Rhizopertha dominica (F.)), the rice

weevil {/Sitophilitë oryza (L.)),

and the Angoumois grain moth

{Sifotroga cerealella (Oliv.)) are

the most destructive insect pests of

rough rice. These insects bore into

the kernels, at times almost completely destroying them. Illustrations of their abundance and the

damage they cause are shown in

figures 6 and 7. The Angoumois

grain moth and the lesser grain

borer are capable of entering the

grain through tlie hull, but the rice

weevil attacks only grains with

broken hulls or with hulls that have

failed to close properly after blooming. In addition to these pests

there are several species that feed

on the surface of the kernels, on

broken grains, and on grains damaged by the boring insects. The

commonest of these are the cadelle

( Tenebroides mauritanicus ( L. ) ),

the saw-toothed grain beetle {Oryzaephilus surinamensis (L.)), the

flat grain beetle {LaemophloeuH

Figure 5.—Crib-type elevator sometimes

used for storing rough rice.
pusillus (Schönh.)), psocids, the

Indian-meal moth {Plodia interpunctella (Hbn.)), the almond

moth {Ephestia cautella (Wlkr.)),

and the rice moth [Gorcyra cephalonica (Staint.)).

Rough rice stored in bulk sometimes suffers considerable damage

from heating that may be partly

attributed to the activities of insects. Active insects generate body

heat and give off moisture, both of

which are absorbed by the surrounding grain, thus producing hot

spots. The grain returned to normal temperature after being fumigated unless other factors were involved in the heating. Conditions

other than insect infestation may,

of course, cause grain to heat.

Damage to rough rice in storage

from insect attack is difficult to estiFigure 6.—Windrows of dead lesser

grain borers on bags and floor in

rough rice warehouse after treatment

with pyretliruni aerosol.

Figure 7.—Rough rice showing exit

holes of the Angoumois grain moth.

mate ; however, a few actual records

will serve to indicate the magnitude

of the losses that occasionally occur.

In one case there was a loss in

weight of 3.23 percent during July

and August from the attack of the

Angoumois grain moth. In another instance rough rice placed in

storage in the fall suffered a weight

loss from miscellaneous insect pests

of 2.2 percent at the end of 6

months, 4 percent after 9 months,

and 10.7 percent at the end of 1

year.

During the 1954-55 storage season in southern Texas observations

were made on the damage caused by

the lesser grain borer to 1 lot of

106,000 barrels of rough rice that

was in storage for 14 months. During this period thei'e was a weight

loss of 2.3 percent, of which 0.6 percent, based on previous observations, was due to normal shrinkage.

Cleaning loss at the mill was 3.1

percent greater than the average

loss expected for rice in storage for

1 season. The total loss resulting

from lesser grain borer damage to

the 106,000 barrels of rough rice
was 4.8 percent. With an average

value of $8 a barrel the loss totaled

$40,704. This loss does not include

the loss in milling yield, or the cost

of fumigating the rice before shipment to the mill.

INSECTS INFESTING MILLED RICE

After the hulls have been removed from the rice the situation

is somewhat different, and some insects of minor consideration in

rough rice become important. The

main offenders in brown and milled

rice, in screenings, and in brewers'

rice are the saw-toothed grain

beetle, the ñour beetles {Triboliwn

castaneum (Hbst.) and T. confusurn Duv.), the cadelle, the flat

grain beetle, the Indian-meal moth,

the almond moth, the rice moth, the

corn sap beetle {Carfophilus dimidiatus (F.)), psocids, the lesser

grain borer, and the rice weevil.

Of these, only the rice weevil and

the lesser grain borer bore into the

kernels (figs. 8 and 9). The others

feed externally, only damaging the

surface of the kernel, but their

presence and the fact tliat they injure the surface of the kernels make

them not only very objectionable

but costly to the industry. In

brown rice the rice weevil is the

major pest and frequently does

much damage. Occasionally the

lesser grain borer infests brown

rice, especially when it is packaged

in paper bags or cardboard cartons.

Practically all rice pests prefer

brown to milled rice.

The larvae of the almond moth,

the Indian-meal moth, and the rice

moth are particularly troublesome

on account of their habit of spinning silken threads. The moth

larvae spin a web as they develop

and leave behind them a silken

thread wherever they crawl, and

when they pupate they attach to the

sack a silken cocoon, which is

rather difficult to remove. The rice

moth larvae spin dense tubes, webbing the kernels into the walls of

Figure 8.—Kernels of milled rice damaged by the rice weevil.

Figure 9.—Characteristic damage to

milled rice from the attack of the

lesser grain borer.
the tube. These webs are difficult

to remove from the rice, and some

rice is lost in the cleaning process.

The practice is to fumigate the

rice and remove the dead insects

just prior to shipping. Both these

processes require costly equipment

and careful manipulation. Badly

infested milled rice must sometimes

be run through a system of brushes

and aspirators to be restored to a

satisfactory condition.

SOURCES OF INFESTATION

Harvesting of rice by combine

has eliminated most of the field in-

^ festation that formerly occurred

when rice was harvested with

binders and left to dry in the field.

Insect infestation may originate

while rice is stored on the farm, in

warehouses, in elevators, and to

^ some extent during transit in railway cars or ships.

Warehouses, (elevators, and storehouses on the farm usually harbor

insects from year to year in feed,

old rice, sweepings, and grain that

has lodged in or dropped through

cracks and crevices in the ñoor and

walls. When insects are present

they almost immediately migrate to

the new rice to start their destructive work, the resulting rate of in-

^ festation and damage depending on

the insect population present in the

storehouse when the new rice is

moved in, the condition of the rice,

and the prevailing temperatures.

Kailway boxcars used to transport rice are likely to carry large

numbers of grain insects concealed

in cracks and crevices and breeding

in accumulations of waste grain

and milled products that have become lodged behind the car linings.

particularly at the ends of the cars.

Infestation of rice shipments is

certain to take place in such cars.

Infested rice arriving at a warehouse, elevator, or mill affords an

opportunity for insects to spread to

insect-free rice already in storage.

Stored-grain insects can and do

enter warehouses and mills by

night. In one experiment, nine

species of stored-grain insects, including the worst enemies of milled

and rough rice, were collected in

insect flight traps at two rice mills.

Insects live and breed in the rice

materials lodged in the milling machinery and infest the rice as it

flows by and through the points of

infestation. These grain deposits

are important sources of infestation

in milled rice. In one study an

average of 425 insects was found

per 1-pint samples of material collected in elevator boots, conveyors,

spouts, and milling units, in a survey of 4 rice mills along the gulf

coast that had been closed down at

the end of the milling season. In

these collections 23 species of

stored-grain insects were identified,

including all the important pests of

stored rice.

GOOD HOUSEKEEPING

Sanitation on the farm, in elevators, warehouses, and in mills will

do much to prevent insect infestation and reduce the losses from this

cause..

432053*'—5T-
Sanitation on the Farm

It is essential that clean, insectfree and weatherproof storage be

provided and that nearby sources of

insect infestation be eliminated. If

possible, metal bins that are easy

to clean should be used. When

wooden bins are employed they

should be thoroughly cleaned, and

as long as possible before they are

refilled they should be sprayed with

a 2.5 percent concentration of

methoxychlor or other materials

approved for this purpose (see

statement on p. 30). A dosage of

2 gallons per 1,000 square feet of

surface area should be applied. If

there are spaces under the floors of

the bins, they should be cleaned out

and sprayed. Waste grain or animal feeds likely to harbor insects

should be removed from nearby

buildings and fumigated so that

they will not serve as sources of infestations to the rough rice.

Sanitation in the Elevator

In addition to cleaning, elevator

bins should be sprayed at intervals

when they are empty, with a residual spray as recommended for

wooden farm bins. In the elevator

proper, remove all junk and unused

machinery, sacking, tools, and

parts, or store them where dust or

waste grain cannot accumulate.

Arrange fire barrels or other equipment so that they will not interfere

with cleaning operations.

Remove waste grain and chaff

from the parts, tunnels, or lower

portions of the elevator. Clean

elevator boots, legs and heads, horizontal screw conveyers, and spouting.

Remove promptly and dispose of

all waste grain and dust gathered

during cleaning operations. Inspect cleaning machinery and dispose of tailovers promptly.

Elevator legs and screw conveyers should be fumigated as often

as necessary to prevent infestation.

A 3-to-l mixture of ethylene dichloride and carbon tetrachloride

or a 3-to-l7 mixture of ethylene dibromide and carbon tetrachloride

can be used at a dosage rate of from

1% pints in the small elevator boots

of country elevators to one-half

gallon in the boots of the large terminal elevators. Screw conveyers

will require about 4 ounces per foot.

Other fumigants are commercially

available that are suitable for this

purpose. They should be used according to the directions of the

manufacturer.

In warm weather the walls of the

tunnels, gallery floor, and head

house should be thoroughly sprayed

with any of the residual sprays approved for this purpose. Sprays

should be applied 3 or 4 times during the spring, summer, and fall.

Sanitation in the Warehouse

Before the warehouse is filled it

should be thoroughly cleaned and

freed of all dust, waste grain, or

other debris likely to harbor insects. Floors should be repaired

and all accumulations of waste

8
grain under the floor or between

partitions should be removed and

disposed of.

Compressed air can be used to

dislodge dust and waste grain from

beams, ledges, and other places in

the superstructure of the building.

After the buildins: has been

thoroughly cleaned and made

weathertight, it should be sprayed

with a residual spray approved for

this purpose.

The use of pallets on the floor is

desirable for sanitary reasons and

to facilitate fumigation of stocks

of rice.

Use of Aerosols and Space Sprays

In rough rice warehouses, aerosols

or space sprays applied periodically

are useful in preventing the buildup of moth infestations. They are

not effective against deep-seated infestations of such insects as the

lesser grain borer, the rice weevil,

or bran beetles, but kill many of

these insects in flight or crawling

on the outside of the bags of rice

(fig. 6).

Aerosol formula:

12.5 percent pyrethrins—piperonyl butoxide (1-to-lO concentrate)

37.5 percent deodorized kerosene

50.0 percent approved solvent

Apply with an aerosol generator

at the rate of 1% gallons per 50,000

cubic feet of warehouse space over

the load every 2 weeks during warm

weather.

In order to avoid the buildup of

residues of pyrethrum and piperonyl butoxide in excess of the established tolerance, it is suggested

that periodical aerosol applications'

be limited to 20 for any 1 lot of rice,

when the space above the load is

approximately equal to the space

occupied by the load ; or be limited

to 10 applications if the load equals

only one-fourth of the warehouse

capacity ; and correspondingly

fewer applications for smaller

loads.

Several types of pyrethrum space

sprays are commercially available.

They should be used as recommended by the manufacturer.

TREATMENT OF ROUGH RICE

The proper care of rough rice

while it is in storage waiting to be

milled will do much to maintain its

high quality and prevent loss in

weight or loss in yield of head rice.

Prompt and timely fumigation

and treatment with aerosols, sprays,

or grain protectives offer the solution of many of the insect problems

of the warehouseman. The following pages contain a discussion of

the methods in use for conserving

rough rice in storage.

Fumigating Rough Rice in Bins

Insects in rough rice stored in granular calcium cyanide. On excovered wooden cribbed bins can posure to air, the calcium cyanide

be satisfactorily fumigated with reacts with the atmospheric mois-
ture to form hydrocyanic acid.

This treatment does not affect the

germination or milling qualities of

the rice, and after the rice is milled,

no undesirable residue is left.

Milled rice should not be fumigated

with this chemical, however, as it

is likely to produce a spotted product.

The fumigant is applied by feeding it into the center of the stream

of rice in the spout, as the bin is

being filled. Specially designed

gravity feed devices that fit into

the calcium cyanide containers are

obtainable for this purpose. The

devices are equipped with graduated dosage plugs so that the fumigant can be run into the rice streams

at any desired rate. A dosage of 8

pounds of the calcium cyanide per

100 barrels, approximately 2é

pounds per 1,000 bushels, or 16

pounds per 1,000 cubic feet of space,

gave a satisfactory kill in covered

wooden cribbed bins. For concrete or metal elevator bins a dosage

of 15 pounds per 1,000 bushels is

satisfactory.

The first 30 and last 30 barrels

of rice run into the bin should be

treated with a double dosage to

compensate for any gas that may

escape.

Eough rice stored in concrete elevators may also be successfully

fumigated with heavier-than-air

fumigant mixtures at the following

dosages per 1,000 bushels: Carbon

disulfide-carbon tetrachloride, 1-to4 mixture, 2 gallons; the ethylene

dichloride-carbon tetrachloride, 3-

to-1 mixture, 3 gallons, or the carbon tetrachloride-ethylene dichloride-ethylene dibromide 60-to-35-to5 mixture, 2 gallons. Other heavier-than-air mixtures are available

which would be suitable for this

purpose. These should be used as

directed by the manufacturer but

only if approved for this use (see

statement on p. 30). In wooden

cribbed bins and farm bins the dosage should be doubled. These fumigants can best be applied in proportionate doses to every 1,000 or

1,500-bushel draft of rice as the bin

is filled. When it is inexpedient

to turn the rice, these fumigants

can be applied by spraying the entire dosage uniformly over the top

layer providing grain temperatures

are 75° F. or above. Milled rice

in bin storage can safely be fumigated with heavier-than-air fumigants. Surface application of dosages recommended for use in

concrete elevators are suggested.

For protection against the vapors

of these fumigants during application the operator should wear

a gas mask equipped with a canister adapted to provide protection against the fumigant being

used.

Control of Surface Infestation of Moths

Surface infestations of rough rice

in elevator bins by the Indian-meal

moth, almond moth, or other species are occasionally troublesome.

In closed top bins they can be combated by applying fumigants in

vapor or atomized form to the overspace. A dosage of 1 pound of

methyl bromide, or commercial

mixtures of methyl bromide with

10
ethylene dibromide, per 1,000 cubic

feet of overhead space will be found

adequate. These fumigants can be

applied whenever flying moths are

seen in the tops of elevator bins or

there is evidence of surface webbing

of the grain.

A synergized pyrethrum spray

is also useful for this purpose.

Commercial formulations are available which should be applied as a

Forced Circulation Method

In recent years the method of circulating fumigants through large

masses of grain has been used successfully for the treatment of bulk

rough rice in flat storage. The

method has the advantage of

greater effectiveness with decreased

dosages owing to the better distrimist in the overspace of elevator

bins, at a rate recommended by the

manufacturer.

As a preventive treatment, a synergized pyrethrum spray can be

applied to the surface of the grain

as a coarse spray after a bin is

fumigated. Any commercial formulation approved for this use can

be used, at the rate recommended

by the manufacturers.

of Rough Rice Fumigations

bution of the toxic vapors. Furthermore the toxic vapors can readily be removed from the rice after

fumigation.

The installation of aerating systems in rough rice warehouses (fig.

10) has encouraged the use o^the

forced circulation system of rice

Figure 10.—System for aerating rovigh rice in warehouse. Central floor duct

consists of concrete tile connected by square wooden boxes from which perforated

floor ducts extend laterally to the walls of the building. The central duct is

connected to a fan capable of moving air through the grain at the desired rate

of air flow.

11
Figure 11.—Closed circulation system within warehouses. Ducts or tunnels from

the wooden boxes of the central floor duct shown in figure 10 extend up through

the rough rice. Fans installed on the tops of these ducts replace the fan used

for aerating the rice and the ends of the central duct are closed.

fumigation since it is a simple matter to adapt such systems for circulation. All that is necessary is

to provide a return duct system so

that air or fumigant pulled down

through the rice or forced upward

through the rice, is returned to the

fan. Essentially the aeration system consists of a central floor duct

from which perforated lateral ducts

extend at regular intervals to the

side walls. The central duct is connected to one or more fans capable

of moving air through the rice.

An air flow rate of 0.1 c. f. m. or

less per bushel of rice has proved

to be sufficient to distribute fumigant gases uniformly throughout

the bulk rice

In some cases the recirculation

system is constructed within the

building by providing ducts or tunnels from the main floor duct extending vertically up through the

rice (fig. 11), with the fan or fans

installed at the top of the ducts

above the top surface. In others

(fig. 4), the lateral floor ducts are

connected to a manifold on the outside of the building and return

ducts from the fan extend to the

overspace above the rice. The

fumigant can be introduced into

either the exhaust or intake side

of the fan.

A dosage of li^ to 2 pounds of

methyl bromide per 1,000 cubic

feet of space has been found to be

12
satisfactory depending on the tightness of the storage structure. Although other fumigants than

methyl bromide can be used in this

method, no dosage rates have been

established for them as yet.

The fumigant should be circulated for 10 to 30 minutes after all

the gas has been introduced or until

it is equally distributed. In practice the circulation system is started

when the gas is first released.

After an exposure period of 24

hours the rice can be aerated and

the fumigant removed.

Steel storage bins and elevator

bins can also be readily adapted to

this type of fumigation.

Heating and Drying Rice

The exposure of the rice to high

temperatures kills the insects.

Temperatures normally used in the

commercial drying of rough rice

are not high enough to kill insects.

An exposure of 10 minutes to a

temperature of 140° F. is necessary

to kill insects infesting stored rice.

Several problems are involved,

however, in subjecting rice to heat.

The rice heats so slowly that the

insects are protected by the rice itself. In experimenting with a

commercial drier using hot-air

blasts, it was found impossible to

obtain a satisfactory kill of insects

in rough rice with air blasts at 140°

for 30 minutes. This treatment

raised the temperature of the rice

to only 122°, which was not high

enough to kill the insects. Furthermore, heating for insect control

is not favored by the rice industry

owing to the danger of causing the

rice to check and because of the removal of too much moisture.

The drying of moist rice and rice

byproducts reduces their susceptibility to insect damage. Insects

infesting stored grain are largely

dependent on the moisture in the

grain for their life processes. Some

species are able to subsist on drier

grain than others. Most of the

insects infesting stored rice prefer

grain having a relatively high moisture content; for example, wheat

grown in the Pacific Northwest is

usually harvested with a moisture

content of 8 or 9 percent and is singularly free from insect damage.

Rice stored in the Southern States,

however, is seldom, if ever, too dry

to sustain insect life.

Synergized Pyrethrum Protective Dusts and Sprays

Pyrethrum powder has often

been recommended for mixing with

grain to protect it from insect

attack.

Pyrethrins synergized with piperonyl butoxide are now available

commercially in both dust and

spray formulations for treating

newly harvested grain or grain

known to be relatively free from

insect infestation.

These formulations afford excellent protection to other small grains

during storage for one season, particularly in the Great Plains region.

For use in protecting rough rice

in storage, in the Gulf States heav13
Figure 12.—Bags of screenings, sweepings, etc. left in the mill harbor many insects.

ier dosages of these dust and spray Experimental work is now underformulations are needed for rice way to determine satisfactory dostlian for wheat in the Midwest, ages.

INSECT CONTROL IN THE RICE MILL

Strict sanitation in the mill is as

essential as it is in the warehouse.

Grain, feed, and deposits of floury

material harboring insects should

not be allowed to accumulate on the

floor, under or near the building,

or in the machinery (fig. 12). As

far as possible machinery should be

arranged so that it can be rendily

cleaned. The building should be

constructed so as to avoid the possibility of damp, dark places.

Floors, walls, and ceilings should

be smooth, to eliminate hiding

places and facilitate cleaning.

Double floors, walls, or partitions

should be avoided. Insects removed in the process of cleaning or

milling the rice should be destroyed

by burning or by treating the accumulations in which they occur

with fumigants.

Insecticidal sprays are quite useful in any mill sanitation program.

Residual sprays can be applied to

the walls of a mill but should not

be applied to the interior or exterior of milling machinery.

Synergized pyrethrum sprays

are effective as contact sprays

against mill insects and can be used

safely inside and outside machinery without danger of hazardous

residues.

When milling machinery is

cleaned out, an oil or water emul14
sion pyrethrum spray can be applied inside the machinery. Many

formulations are available commercially. They should be used as directed by the manufacturer.

A general fumigation of the mill

proper once a year with HCN or

methyl bromide is desirable. This

may be done in conjunction with

the warehouse fumigation described in succeeding pages and at

similar dosages.

As a supplementary measure the

local fumigation of elevator boots

and other milling equipment containing milling stock that may harbor insect infestations, at monthly

intervals during the milling season,

will serve to hold the insect population of the mill to a low level.

Finnigants in common use for this

purpose are the 3-to-l mixture of

ethylene dichloride and carbon tetrachloride, the 3-to-l7 mixture of

ethylene dibromide and carbon

tetrachloride, and a mixture of 70

percent ethylene dibromide, 29.5

percent methyl bromide, and 0.5

percent inert ingredients. The

amount of material required for

each milling unit depends upon its

size. The recommendations of the

manufacturers should be followed.

Millers applying their own fumiFigure 13.—Metal containers used for

collecting tailings from rice-cleaning

machinery. The tailings fall into the

container through a funnel which is

heated by an infrared-ray lamp to prevent the escape of insects. After the

container is ñlled, it is fumigated to

kill the insects in the tailings, or the

tailings may be removed and fumigated. A glass window has been inserted in the container to show when

it is full.

gants should wear suitable gas

masks and take precautions described in the section on fumigants.

Treatment of Tailings From Cleaning Machinery

Tailings from rice-cleaning machinery usually contain many insects that, unless properly disposed

of, are likely to spread to stocks of

uninfested rice in the mill. In

many cases the tailings are caught

in burlap sacks that, when filled,

are set aside for an indefinite period

without treatment. To avoid infestation from this source, a satisfactory method has been devised

for collecting the tailings in a tight

metal container (fig. 13) which

should be large enough to hold a

day's run of tailings. To prevent

the escape of insects from such a

15
container while it is being filled,

arrangement can be made for the

tailings to fall into the container

through a metal funnel heated by

means of an infrared lamp. The

insects will not climb up over the

heated sides of the funnel; hence

they are unable to escape. The

tailings can be treated overnight in

the container with a mixture composed of 75 percent ethylene dichloride and 25 percent carbon tetrachloride at the rate of about 1%

ounces of the mixture per 100

pounds of tailings, or the tailings

may be removed from the container

and fumigated immediately. If

the tailings are treated in the

container in which they are collected, mills operating on a 24-hour

basis should have two of these containers, to be treated alternately.

TREATMENT OF MILLED RICE

Warehouse Fumigation

The fumigation of entire warehouses filled with pockets of milled

rice is being practiced successfully

in buildings that are or can be made

gastight. Efficient fumigation arrests the insect infestation and damage until the plant becomes reinfested from outside sources. Usually only one or two treatments a

year are necessary to keep the contents of a tight warehouse reasonably free from insect damage. The

number of fumigations required

depends on the quantity and condition of the rice carried over from

one season to the next, entry of insects from outside sources, and the

effectiveness of the first treatment.

Ordinarily if new-crop rice is

stored in a clean warehouse, one

fumigation about midsummer is

sufficient, provided there is no reinfestation from outside sources.

If rice is carried over from one season to the next, however, or if insects from outside sources fly into

or otherwise enter the warehouse,

an early summer and a fall fumigation are sometimes necessary. A

second fumigation also becomes

necessary when the first proves unsuccessful. For warehouse fumigation both hydrocyanic acid and

methyl bromide are effective.

All polish, bran, sweepings, and

other materials that harbor insect

pests and are difficult to penetrate

with the fumigant used should be

treated separately in an atmospheric vault or vacuum chamber

when preparation is being made for

mass fumigation of milled rice in

pockets. Where this is not feasible,

the dosage of fumigant should be

increased to take care of the situation. All windows, doors, eaves,

and other openings in the building

should be closed and carefully

sealed with laminated paper and

paste, or with putty. Ventilators

can be sealed on the outside by covering with a plastic sheet (fig. 14).

This is essential; otherwise the gas

will escape, thereby preventing the

building-up of a concentration fatal

to insect life.

Liquid Hydrocyanic Acid for Warehouse Fumigation

Hydrocyanic acid is a satisfactory fumigant for milled rice stored

in pockets in a reasonably tight

16
BN-4159

Figure 14.—Roof ventilator sealed on outside by covering with plastic sheeting.

building or for rough rice in bags.

Although this gas can be produced

in several ways, only the liquid

method will be discussed, as this has

been used "almost exclusively for the

fumigation of rice warehouses.

Liquid hydrocyanic acid (96 to 98

percent HCN) is a volatile, colorless liquid boiling at 79.7° F. It

evaporatesto form a gas, the specific

gravity of which is 0.93 as compared

with air. It is marketed in cylinders containing 30, 75, and 166

pounds of liquid. Hydrocyanic

acid is extremely poisonous to

human beings, although it can be

used safely if properly handled.

This fumigant does not injure the

quality or color of the rice.

Liquid hydrocyanic acid is usually applied through a piping system of %-inch soft, seamless copper

tubing installed throughout the

building. Disk-type spray nozzles,

so spaced as to insure uniform distribution of the gas, should be provided, one for each 10,000 to 15,000

cubic feet of space. Special pressure-type nozzles now on the market

are fitted with a device to prevent

clogging and need not be removed

for cleaning. The inlets to the piping system, one for each floor, are

at convenient points outside the

building, usually on the loading

platform (fig. 15). The cylinders

of hydrocyanic acid are connected

to the piping inlets by means of

short lengths of special rubber hose,

or, if desired, a manifold arrangement may be used. The liquid is

forced into the warehouse by means

of air pressure applied to the cylinders. When an air compressor is

not readily available, a cylinder of

compressed nitrogen makes a good

substitute (fig. 16). One cylinder

of nitrogen supplies enough presU
Figure 15.—Cylinder of liquid hydrocyanic acid and air compressor placed

in readiness to fumigate a rice warehouse.

sure to empty approximately ten

75-pound cylinders of HCN.

A dosage of 16 to 24 ounces of

liquid hydrocyanic acid per 1,000

cubic feet of space is recommended.

The exact dosage required will depend upon the temperature of and

the quantity of rice in the building—the lower the temperature and

the larger the quantity of rice, the

higher the dosage should be. Both

rice bran and polish require a considerably higher dosage than the

rice itself.

An exposure of 72 hours should be

allowed, after which the building

may be opened for aeration. A gas

mask should be worn by the operator while he is opening the

building.

Methyl Bromide for Warehouse

Fumigation

Methyl bromide is another fumigant found to be well adapted for

treating rough or milled rice stored

in bags in tight warehouses. This

fumigant is a colorless liquid which

boils at 40.1° F., thus making it

effective for fumigating at reasonably low temperatures. The specific gravity of the liquid is 1.732 at

32°. At ordinary temperatures,

when not confined under pressure

in containers, it is a gas. It is noninflammable and stable, has a low

water solubility, has remarkable

powers of penetration, and is relatively inexpensive. In low concentrations methyl bromide does not

have a distinctive odor, but in high

concentrations a sweetish odor approaching that of chloroform may

be perceived.

Methyl bromide is obtainable in

liquid form under low pressure in

cylinders containing 10 to 200

pounds net, or in 1-pound cans.

The pressure within the cylinders,

due to the vapor pressure of the

Figure 16.—Cylinder of nitrogen attached to HCN cylinder. One cylinder of nitrogen supplies enough pressure to empty ten 75-pound cylinders

of HCN.

18
methyl bromide, will vary with the

temperature. At high temperatures

it is sufficient to eject the liquid

forcibly from the cylinder when the

valve is opened, whereas at 40° F.

the pressure gage reads 0. To

facilitate its use at all temperatures,

therefore, the pressure normally

occurring within the cylinder is

increased by charging it with sufficient air at the time of shipment

to eject all the liquid forcibly, even

at temperatures below 40°.

The cylinders are equipped with

siphon tubes extending to the bottom so that the pressure will cause

the liquid to issue from the exit

port at the top when the valve is

opened, without the necessity of

inverting the cylinder.

Methyl bromide may be applied

in several ways for the fumigation

of rice in warehouses. It is usually

released from a number of locations

in the warehouse so as to insure a

uniform distribution of the gas.

The fumigant is released above the

rice near the ceiling through a

length of i^-inch copper or plastic

tubing connected to the exit port of

each cylinder, the open end of the

tube being plugged or pinched shut

and two %-inch holes bored

through the tube near the closed

end so that the liquid is ejected

horizontally in opposite directions

above the rice (fig. 17). In some

cases the plastic tubing is dispensed

with and a special fitting is attached

to the exit port of each cylinder

which directs the fumigant upwards

instead of horizontally (fig. 18).

The pressure in the cylinder is

sufficient to force the fumigant into

the overspace above the rice and

Figure 17.—Methyl bromide cylinder

with copper tubing attached so as to

release gas near ceiling of warehouse.

In many cases plastic tubing connected to the cylinder is led up to the

ceiling and fastened so that the free

end will discharge the gas above the

stacks of rice.

give a good distribution of the

vapors.

The men who release the fumigant must wear gas masks

equipped with canisters that give

protection from methyl bromide,

and they should begin first with

the cylinders farthest from the

exit, opening each valve completely and working toward the

door. The door left unfastened

for exit should be sealed immediately after the persons releasing the gas have left the building.

The liquid evaporates as soon as it

is released. Circulating fans

should be operated inside the ware19
house during the period of fumigation to facilitate the distribution of

the gas. If desirable, the metliyl

bromide can be applied from the

outside through a piping system

similar to that described for the use

of liquid hydrocyanic acid. When

this latter method of fumigation is

used, the pressure in the cylinder

should be increased to 150 pounds

Figure 18.—Methyl bromide being released during the fumigation of a rice warehouse. The special ñtting atached to the exit port of the cylinder directs the

fumigant upwards.

20
Figure 19.—A battery of three atmospheric vaults of frame construction lined with

24-gage galvanized sheet metal. These vaults have a combined capacity of 2,000

pockets of milled rice. One discharge fan is used to ventilate all three vaidts.

Note the convenient arrangement by which the doors are swung out of the way

during the loading and unloading of the vaults.

by charging it with compressed air

to insure the complete ejection of

the methyl bromide. In cool

weather the pressure in the cylinder

may have to be renewed in order to

empty it quickly.

A dosage of 1 pound for milled

rice and ly^ pounds for rough rice

per thousand cubic feet of space is

recommended for a satisfactory insect kill. An exposure of 16 to 24

hours should be allowed, and after

this the building can be opened for

aeration. The workmen opening

the building should wear gas masks.

Ordinarily it requires from 4 to 8

hours to aerate a building fumigated with methyl bromide so that

it may be entered safely without a

gas mask. The speed of ventilation

will, of course, depend upon the

number of windows and doors

opened and the draft of air through

the building.

Atmospheric-Vault Fumigation of Milled Rice

Small lots of rice or rice products

are economically treated in a gastight room of suitable size, commonly known as an atmospheric

fumigation vault or chamber, because the treatment is made at

atmospheric pressures. Such a

fumigation chamber may be constructed of any material that can

be made gastight (fig. 19). Sheet

metal, plywood, masonite, or even

concrete linings are satisfactory.

The latter three types need to be

coated with a gas impervious paint.

Suitable doors, complete with

frame and rubber gasket, may be

21
Figure 20.—View of interior of small

vault, showing fan used to circulate

the fumigant or to eject it from the

vault.

purchased already assembled, or a

tight door can be constructed on the

lid principle, the flat surface of the

door being turned toward the door

frame of the chamber. A rubber

gasket attached to the door frame

on the chamber makes a tight seal.

The door should be fastened in

place by means of bolts extending

through it from the casing on all

four sides. Hinged doors are hard

to fasten tightly unless the hinges

have loose joints which allow the

door to be drawn up against the

casing by means of bolts.

A fan can be used satisfactorily

for circulating the gas within the

vault during the treatment and also

to eject the gas afterward (fig. 20).

The size of the fan to be used depends on the size of the chamber.

It should be large enough to change

the gas in the chamber twice per

minute. If the fan is mounted on

the inside of the chamber, an explosion-proof motor should be used.

The rice is usually cleaned and

resacked after fumigation in order

to remove dead insects.

In handling the fumigated rice a

ventilating hood equipped with a

suction fan should be placed over

the hopper, as shown near the top

of figure 21, to carry off any fumes

released from the rice and to insure

the comfort and safety of the workmen.

Fumigants used have had tolerances for residues established under

Public Law 518, since milled rice,

as well as rough rice, is a raw agricultural product. Two fumigants

approved for this use are discussed

in the following pages. If other

fumigants are to be used, consult

the label or the container to be sure

they have been approved for this

use, and that tolerances have been

established for their residues on

rice.

Methyl Bromide for AtmosphericVault Fumigation

Methyl bromide has been found

to be a highly effective and comparatively inexpensive fumigant

for the treatment of milled rice and

rice products. In atmosphericchamber fumigation, methyl bromide is introduced from the outside

through the wall by means of a

1/4-inch plastic or copper tube. The

22
Figure 21.—Mixing-hopper room in rice mill showing, near top of picture, the

ventilating hood over the hopper into which the fumigated grain is being dumped.

dosage and exposure time will depend on the type of container in

which the rice is to be packaged,

the time available for fumigation,

the temperature, and the quantity

of rice contained in the vault. The

dosages shown in table 1 have given

satisfactory results for the fumigation of milled and brewers' rice at

70° F. and over, in a gastight chamber equipped with a circulating

system (see statement p. 30). The

dosage and the exposure period

must be increased when rice is being

fumigated at lower temperatures.

After fumigation the treated rice,

still in the chamber, should be aerated. This requires approximately

1 hour, depending on the size of tlie

exhaust fan. The gas having been

expelled in this way, the workmen

may safely handle the rice without

wearing gas masks.-

TABLE 1.—Dosages of methyl hromide giving satisfactory results

in the atmospheric-vault fumigation of milled rice at 70° F. and

over

MiniDosage mum

Type of Expo- per 1,000 dosage

package sure pounds per 1,000

period of rice cubic

feet of

space 1

Burlap or Hours Ounces Pounds

cotton bag- 4 VA 1%

Do 6 1 1/2

Do 12 % %

Carton 15 1% 1%

1 Do not use less regardless of size of load.

23
Liquid Hydrocyanic Acid for Atmospheric-Vault Fumigation

Excellent results in the fumigation of bagged milled rice in atmospheric vaults can also be obtained

with liquid hydrocyanic acid gas.

Dosages of li/^ ounces per thousand

pounds of rice, or 21/2 pounds per

thousand cubic feet of space, for a

4-hour exposure, and 1 ounce per

thousand pounds of rice or li/^

pounds per thousand cubic feet of

space for a 15-hour exposure, were

found satisfactory when the temperature of the rice was 80° F. or

above.

The fumigant is introduced into

the vault through a short piping

system. In all cases the fumigant

should be circulated in the vault

during the exposure by means of a

fan.

Vacuum Fumigatiçn

In vacuum fumigation the rice is

placed in a steel chamber from

which a large proportion of the air

is subsequently evacuated by a

pump and then is replaced with a

fumigant (see inside front cover).

By this method the gas penetrates

the rice with much greater rapidity

than in atmospheric fumigation.

This permits shorter exposures than

at atmospheric pressure, especially

when tightly packed materials are

being treated.

Vacuum fumigation chambers are

made in many sizes, the larger ones

being capable of holding one or

more carloads. Both cylindrical

and rectangular chambers are available.

At the end of the period of exposure the chamber is aerated by

pumping the fumigant out of the

tank and breaking the vacuum with

air. Usually the fumigated products are "air-washed" several times

by alternately drawing and breaking a vacuum of about 28 inches.

Another very satisfactory method

of ventilating the vacuum chamber

is by the use of an exhaust fan. In

this method the vacuum is broken

at the end of the exposure ; and, as

normal atmospheric pressure is approached, the discharge fan is

started, and the chamber door from

which the unloading is to begin is

opened. This method is more rapid

than that of breaking and pumping

several vacuums and makes it unnecessary to operate the exhaust

pump. The discharge fan should

be operated while the workmen unload the fumigated products. As

in the case of atmospheric vaults,

the exhaust pipe should carry the

gas to a safe point outside the building.

Liquid Hydrocyanic Acid for Vacuum

Fumigation

Liquid hydrocyanic acid is highly

satisfactory for the vacuum fumigation of milled rice and rice products. For maximum eíRciency the

hydrocyanic acid should be let into

the vacuum chamber in the gaseous

form. This is accomplished by

drawing the liquid from the cylinder through a volatilizer.

Eice readily absorbs hydrocyanic

acid and very slowly liberates it on

exposure to the air—a feature that

is of considerable advantage, since

the insecticidal effect persists for

24
some time after the rice has been

removed from the vault. Unless

fumigated rice is stored in a tightly

closed room the slowly liberated gas

is not likely to accumulate in quantities dangerous to any person.

Treated rice can be run through an

aspirator immediately after the

fumigation and still retain enough

gas after it is resacked to be lethal

to insects—an effect known as postfumigation.

The dose for vacuum treatment of

rice with hydrocyanic acid depends

on the type of chamber, the length

of exposure, and the temperature of

the rice. For treating rice at 60° F.

or above, a dosage of li/4 ounces per

thousand pounds of rice, and never

less than a minimum of 1% pounds

per thousand cubic feet of space,

has been found satisfactory at a

3-hour exposure for rice in burlap

and cotton pockets, and cartons of

all types.

After the fumigation the chamber should be air-washed twice before the workmen are allowed to

enter to handle the treated products. When a strong discharge

blower is used, it may be safe to

enter the vault after 5 minutes of

aeration. The fan should be operated during the entire time the rice

is being unloaded, except when

Fumigation of Rice

Milled rice in pockets and rough

rice in bags or in bulk can be successfully fumigated in all-steel

grain boxcars that are tight and

that have been properly sealed. If

possible the cars should be prepared

for fumigation before they are

loaded, one door and all cracks beplenty of time has been allowed for

aeration.

Methyl Bromide for Vacuum Fumigation

The dosage required depends on

the temperature, the length of the

exposure period, and the type of

container in which the rice is packaged. For treating rice at 65° F.

or above, the dosages shown in table

2 have been found to give satisfactory results.

TABLE 2.—Dosages of methyl hromide required under various contions for fumigating milled rice

in a vacuum chamber

Type of

package

PocketDo

Do

Carton,

Do

Do

Dosage

Expo- per 1,000

sure pounds

period of rice

Hours Ounces

2 1%

3 %

12 'Á

2 2

3 W2

12 1/4

Minimum

dosage

per 1,000

cubic

feet of

space 1

Pounds

3

2

1

4/4

3

2/2

1 Use no less regardless of size of load.

After the fumigation, the rice is

aerated by the same methods as described for vacuum fumigation with

hydrocyanic acid.

in Railway Boxcars

ing sealed from the inside with

masking tape or putty, and oil (fig.

22). Car floors can be made more

gastight by covering them with a

layer of laminated paper that will

not "bleed" due to the pressure of

the load.

Wooden cars are not as satisfac25
Figure 22.—Sealing railway boxcar for fumigation.

BN-4147

(Courtesy of H. T. McGill.)

tory as steel cars since it is difficult

to make them tight enough to hold

a high concentration of fumigant.

When it is necessary to use them the

dosage must be increased to offset

the greater leakage.

For the fumigation of bagged

rice, either milled or rough, methyl

bromide or hydrocyanic acid can

be used. Of the two fumigants,

methyl bromide is most commonly

used, owing to the ease of application and aeration.

If methyl bromide is used a dosage of from 10 to 12 pounds per car

for steel cars and 12 to 15 for wood

cars is recommended, based on the

quantity of rice in the car and the

temperature of the rice. The methyl

bromide is applied by means of one

or two 14-inch plastic tubes inserted

through a crack in the doorway and

extended to a point above the rice.

The upper ends of the tubes should

be plugged, und i/g-inch holes

drilled in each side to allow the

fumigant to be ejected horizontally

in opposite directions above the rice.

Liquid methyl bromide can dissolve

the asj)haltic compounds used on

freight car ceilings, therefore the

discharge from the tube should be

directed so that no liquid strikes the

ceiling. The tubes should be fastened near the ceiling with string or

soft wire and tacks, but lightly

enough so that they can easily be

pulled loose and withdrawn after

the gas is applied.

The same precautions should be

taken in the application of methyl

bromide and in the aeration of the

car after fumigation as is required

for its use in atmospheric vaults.

26
Hydrocyanic acid can be used at

a dosage of li/^ ounces of liquid

hydrocyanic acid per thousand

pounds of rice with a minimum

dosage of 1% pounds per thousand

cubic feet of space for a 72-hour

exposure.

For the fumigation of rough rice

in bulk in railway boxcars any of

the heavier-than-air fumigants recommended for the fumigation of

rough rice in farm bins can be used

by applying uniformly over the

surface of the grain, at the same

dosages.

Where complete and quick kills

are essential, bulk rice in boxcars,

both milled and rough, may be

fumigated with methyl bromide by

the recirculation method. By this

method 10 steel probes 6 feet in

length with perforated tips are inserted in the grain equidistant in a

line down the center of the car (fig.

23). The probes are connected by

a duct system to a blower inserted

in the middle of the system. When

in operation, air is withdrawn from

the floor level and discharged into

the headspace, thus setting up recirculation. To simplify things the

duct system can be constructed with

a length of metal spouting to serve

as a manifold. The blower should

have a capacity of not less than 625

c. f. m. against 5-inch static pressure. The entire system should be

set up inside the car.

The fumigant can be introduced

through a 14-inch plastic tube into

Figure 23.—Interior of railway boxcar

filled with rice, showing metal probes,

duet system, and blower for circulating methyl bromide through rice.

the air space above the grain and

the blower allowed to run for 30

minutes after the gas is applied. A

dosage of from 12 to 15 pounds per

car of methyl bromide will be found

satisfactory.

All fumigated cars should be

placarded on both side doors with

a red card showing that the car

has been fumigated, giving the

date, naming the fumigant used,

and warning against entry before

aeration.

In the case of cars fumigated with

liquid HCN or methyl bromide it

will be necessary to aerate them

before they are shipped.

Fumigation of Rice Under Gastight Sheets

In warehouses that are too loosely

constructed for successful fumigation, or in large storages where it

would be impractical to fumigate

the entire space, it is advantageous

to fumigate individual stacks of

27
Figure 24.—Tarpaulin covered stack of rice, also sheet of polyethylene plastic

material laid out ready to cover another stack.

bagged rice under a gastight tarpaulin (figs. 3 and 24). In some

cases the plastic covers may be left

in place over the stacks as long as

they remain in the warehouse.

These covers then serve to protect

the stack from reinfestation by flying insects and are always ready for

an additional fumigation as required. Polyethylene sheeting

makes an inexpensive covering for

this purpose. A 3-mil gauge sheet

is heavy enough where it is to be

left in place; however, if it is to be

moved from one stack to another,

4-mil or 6-mil gauge sheeting should

be used. Other materials that can

be used are plastic-coated nylon,

plastic-coated canvas, balloon cloth,

or rubberized fabrics.

A plastic tube connected to a

cylinder of fumigant can be used

to introduce the gas at the top of the

stack in one or more places depending upon the size of the stack. In

very large stacks it is desirable to

connect the cylinder to two or more

nozzles installed in wells made by

stacking the top layer of bags in an

appropriate pattern. In most cases,

however, it is only necessary to use

a single open-ended plastic tube to

introduce the gas. An air dome at

the top of the stack should always

be provided so that the gas can be

introduced without wetting the

plastic sheet.

The plastic tube from the cylinder can be run up from the base of

the stack or introduced through a

28
hole in the tarpaulin. After the

gas is introduced the tube can be

withdrawn and a patch pasted over

the entry point.

The base of the stack should be

made airtight by the use of "sand

snakes."

Dosages of II/2 pounds of methyl

bromide or 11/2 to 21/2 pounds liquid

HCN per 1,000 cubic feet are recommended for the fumigation of

bagged, milled, or rough rice at

temperatures of 70° F. or above.

At lower temperatures it is necessary to increase these dosages in

order to obtain complete kills. To

facilitate penetration of the gas it

is recommended that all rice be

stacked on pallets.

Precautions m the Use of Fumigants

Fumigants toxic to insects are

also toxic to human beings and

animals. In handling them, the

operator should take all necessary precautions and follow all

directions given on manufactured

products. Care should be taken

not to breathe the vapors or spill

the liquid fumigants on the skin

or clothing. Unless the operator

is acquainted with the fumigant

and methods of using it, it is preferable before undertaking fumigation work to have a professional or experienced fumigator

instruct the workmen who are responsible for its use, or, in large

operations, to have it done by professional fumigators.

Gas masks equipped with canisters of the proper type for protection against the particular fumigant being used can be relied

upon for complete protection

only against low concentrations

encountered around the equipment being used and the outside

of bins. They are not to be used

in the bins or in other high concentrations of the gas. Even

where used in light concentrations, a canister should not be

used for more than the period

recommended by the manufacturer and after that time it

should be replaced by a fresh,

unused canister. The only complete protection from high concentrations is to use an air-line

mask supplied with air from a

safe source and have the entire

skin area protected.

29
CAUTION

A Federal law (518, 83d Congress) known as the Miller amendment to

the Food, Drug, and Cosmetic Act, provides for establishment of safe

tolerances for residues of useful insecticides on raw agricultural products.

Both rough and milled rice are classed as raw agricultural products.

Insecticides which leave no residue may, of course, be used on or around

rice without regard to any tolerance. But most insecticides do leave a

residue, and should be used on or around rice only if they are insecticides

for the residues of which, on rice, tolerances or exemptions from the

requirement for a tolerance have been established; and should be used

only in such a way that their residues will not exceed their respective

tolerances.

Directions for use of a pesticide, appearing on its label, are subject to

clearance under another Federal law, the Insecticide, Fungicide, and

Rodenticide Act. Such clearance is withheld if it appears likely, on the

basis of experimental evidence, that the usage proposed would contribute

residue in excess of the applicable tolerance; or, in event no applicable

tolerance or exemption exists, if the proposed usage would be likely to

contribute any residue.

For these reasons, it is the joint opinion of the Food and Drug Administration of the Department of Health, Education, and Welfare and

of the Pesticide Regulation Section of the Department of Agriculture,

that labels of pesticides in commercial channels should generally furnish

a reliable guide to their usage in such way as to avoid incurrence of

excessive residues.

Some pesticides contribute residue that is cumulative with repeated

treatment. When, for example, rice is fumigated with methyl bromide,

a certain amount of fixed bromide residue accrues from each fumigation ;

if repetition of fumigation were unlimited, a residue in excess of the

tolerance would eventually accrue. Users of methyl bromide are cautioned

not to fumigate rice more than three times at recommended dosage. If the

fumigation history of a particular lot is unknown, or if it is known that

it has already been fumigated three times with methyl bromide, it should

not be refumigated with methyl bromide, or other bromine-bearing fumigant, unless chemical analysis for already-incurred bromide residue is

first made, and such analysis establishes that there remains adequate

tolerance allowance for the additional residue to accrue from the contemplated fumigation.

U. S. GOVERNMENT PRINTING OFFICE: 1957

For sale by the Superintendent of Documents, U. S. Government Printing OíRee

Washington 25, D. C. Price 15 cents

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