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Historic, archived document
Do not assume content reflects current scientific knowledge, policies, or practices.
Marketing Research Report No. 334
Pyrethrum Mists and Aerosols for Control of Insects
in Tobacco Warehouses
Marketing Research Division Agricultural Marketing Service
U.S. DEPARTMENT OF AGRICULTURE
CONTENTS
Page
SUMMARY. ssi.) Ae wre v0) wholes .(e,"0cs\ evo ie. 'e.leile ove @ 0, eve ois \eliet’si.alg) ener cuemenomene deen neier RCE 5 1 ImGLOGWCEIOMs sieve aces siete ¢ ehotcEonal Wel ietele ai's) ae le 6 ie al sicle \e, © elle taal sel a efoter aye aifa lela olohoteletejare 1 WG arIPETTSTUOTES iter, aistone tere tatere <14 ote 4 AD ago s Hie, 0b (ege\ce/ elfeonehe Choreleuecrenekeiore: <teteae kon 2 Advantages of pyrethrum ...... SOOMO DOC OG OOOO COO OMIOL MOO OUOOOU OUD ROO OU UO 3 Difference between sprays, mists, and aerosols .......+ch sneha AGOGO DDL 3 Ode ES ian wale ohvevev<.ove(s cPalers v.56) s' 6 sce 4 ana d= aha, em Gat ese eee sfolesonefelelatstohences pots 5 DVNETSUSTS iss ai taie laerevee pucKelie lel afisiinselie; s/ elke ila (elelstatalParevelel ort or eiaian oliewe aL e\icfenoitoied ofaien weit oeuciens 8 Concentrationvand dosage. sis «sic. as iis lleliai/a leis! '5j's\"s) « 66) csifepetounie aie Romouemonenasne olerereiopekelone oes 8 sublethaljeffectrot-pyrethrum On cigarette beetles ..2.> sa ane see cee eee S06 1 Ere quency, Ofapplication sso. .s «ss AOOH OOO siislione elelelehojtetetercteie FO GOCGe AdoooogoaC 11 PUNICHOL APPL ICACL OM Gs. io.ce \a oe Ses 0a 6 aioe so) ae slGre lols ole, el deren ene aetehe ORS eae rete Wal Technique of application’....... a0. 1nje! «ei (01\shte fa, olis'(el elleyeiin fol eke raja tal suelo) olien Momere kel enone hon neiovenetens 13 Hifectivieness oftepycethrum mists and aAeGrOSOLSire sieeleicletede/sherelelonenetotel Censierer-Vehorchenees 13 AGainsitetiemtODACCONMMOLH Garsienereleleletenel eyoreneistehenekemelonere AOI. DIDO OOO D S050 b0DGC 13 ACalnstatbegei gamete DC CTLE i.e.) lelelslc sie) sielehoens i.e foils: el ayaiiee(olints « ee) a eiete = iaie’siaterahe NS} Effect of temperature 3... s.% «2.6 RoOaoUpoodoonc aekeltalelel enat starts Sooudoo Odo oUUO ods 17 Tite GAtUTesCtLe Caste atsterereis sles 66 oss slots oieke lohetete venoneters SA bic ol6.c SS ub Oa OD OD o oe 18
ACKNOWLEDGMENTS
The author is indebted to W. D. Reed (now with the Department of Defense), R. W. Brubaker, A. H. Yeomans, C. O. Bare, and Dana P. Childs, of the U. S. Department of Agriculture; to ©. C. Scott, of the Flue-Cured Tobacco Cooperative Stabilization Corporation; to J. P. Vinzant, of the American Tobacco Company; to C. D. Delamar, of Liggett & Myers Tobacco Company; to C. M, Sprinkle, of R. J. Reynolds Tobacco Company; and to various tobacco companies for advice, assistance, and cooperation.
This report is a part of a broad program of research to reduce the cost of market- ing farm products, in this instarice by reducing the cost of controlling insect infestation in stored tobacco.
For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington 25, D.C. Price 15 cents
PYRETHRUM MISTS AND AEROSOLS FOR CONTROL OF INSECTS IN TOBACCO WAREHOUSES
By Joseph N. Tenhet Stored-Tobacco Insects Laboratory, Richmond, Va.1
SUMMARY
Pyrethrum mists and aerosols have been used extensively in tobacco warehouses and factories for the control of the tobacco moth, Ephestia elutella (Hbn.), and the cigarette beetle, Lasioderma serricorne (F.). Both types of treatments are highly ef- fective against the moth but relatively ineffective against the beetle.
Mists and aerosols are not as effective as fumigation for controlling the cigarette beetle. However, they are very useful for controlling insects in loosely constructed buildings where fumigation cannot be used.
The difference between mists and aerosols is in the size of the particles produced, the mists having the larger. Because of this fact, the mists can be used in both open and closed warehouses whereas the use of aerosols is restricted to closed or semi- closed buildings.
The highly refined, very volatile hydrocarbon oil used in these studies proved quite satisfactory. Heavy oils are undesirable because they leave an objectionable greasy deposit in tobacco warehouses.
Synergists for pyrethrum, when used as a contact insecticide, appeared to be of little value against the cigarette beetle.
Concentration of insecticide in the mists and aerosols should be 0.2 percent pyre- thrins for the moth, and 1 percent for the cigarette beetle. For the mists, the insecti- cide should be applied at the rate of 3 fluid ounces per 1,000 cubic feet of air space, and for aerosols at 2-1/4 to 3 fluid ounces. In small warehouses where the method of storing tobacco permits unusually good distribution of an aerosol, the dosage and con- centration sometimes can be slightly reduced. Applications are usually made 1 to 3 times a week but may be made daily if necessary. Weekly applications will control the tobacco moth; daily applications often may not control the cigarette beetle.
Aerosols and mists kill only those beetles that emerge from the tobacco, but since some beetles complete their life cycle and reproduce within the tobacco hogshead, con- trol is not complete.
For the cigarette beetle, mists or aerosols should be applied between 5 p. m. and midnight, and should be concentrated in the upper areas of the warehouse.
INTRODUCTION
Pyrethrum mists and aerosols have been used extensively in tobacco warehouses and factories to control the tobacco moth and the cigarette beetle. They are highly effec- tive against the moth, but much less so against the beetle. A pyrethrum mist, originally called a ''space spray,'' was developed to control the tobacco moth in open-type storage warehouses. It did this most efficiently. Later, an effort was made to adapt this treat- ment to control the cigarette beetle in all types of warehouses and factories. This was much less successful. Many misconceptions have arisen as to what can be expected of mists and aerosols. This method of applying insecticides has certain inherent limitations.
1 This laboratory is a field station of the Stored-Product Insects Section, Biological Sciences Branch, Marketing Research Division, Agricultural Marketing Service, U. S. Department of Agriculture.
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The object of this paper is to explain how, where, and why pyrethrum treatments are effective, and where and why they may not be effective.
The terms "fumigation, '' ''spraying,'' and ''fogging'' are often misapplied. They are not the same, but are three different treatments:
Fumigation is the use of a gas, lethaltoinsects, either in vacuum, in atmospheric chambers, or in a warehouse or factory. This is one of the most efficient means of in- sect control. It not only kills the insects in the air space, but the gas penetrates into the hogsheads, cases, or bales, killing the eggs and immature stages of the insects within the tobacco. However, a warehouse must be almost airtight to be effectively fumigated. Often this is not practical.
'Spraying'' generally refers to the use of mists, which are relatively fine sprays, applied to the airspace in a warehouse, usually by means of especially designed, mobile, electrically powered blowers. A mist has larger droplets than an aerosol, and usually is a contact insecticide that kills those insects actually hit by the spray particles. It does not penetrate the hogsheads, bales, or cases of tobacco, and consequently does not reach many of the eggs or immature stages of the insects; but it has one big advantage-- it can be used against the cigarette beetle or the tobacco moth in open sheds where fumi- gation or aerosols cannot be used.
An aerosol consists of extremely small particles suspended in the air. The use of thermal, or heat-generated, aerosols is often called ''fogging.'' The same insecticides used in mists are also used as aerosols, and the aerosol particles, like those of a mist, must hit an insect to kill it. Aerosols do not penetrate tobacco or containers, and there- fore do not usually reach the eggs or immature insect stages. Aerosols can be used in buildings that cannot be fumigated because of cracks and small openings in the floors, walls, or roof. They are not effective in open sheds.
In tobacco warehouses, both mists and aerosols are more of a preventive measure than a control. They are aimed at killing the adult insects before they have time to lay many eggs. If treatment is applied so infrequently that an appreciable number of eggs are deposited before beetles are killed, the purpose of the treatment is defeated. There- fore, treatment must start as soon as the insects become active in the spring and continue | throughout the summer until cold weather terminates activity. Treatment must be per- | formed regularly even though few adult insects are observed. Even a few insects can lay many eggs, and once the eggs are laid an infestation has started. The larvae do the damage, and they are not reached by sprays or aerosols.
EARLIER STUDIES
The tobacco moth was first reported as a major pest of tobacco in the United States in 1930 (1).2 Shortly thereafter, Reed and Vinzant (3) developed the use of pyrethrum dusts to control this insect. These dust treatments were fairly effective against the moth, but of little or no value against the cigarette beetle, which was usually present also. Furthermore, accumulations of spent dust in the tobacco warehouses presented a physical nuisance as well as a fire hazard.
In 1938, laboratory tests were begun at Richmond, Va., in an effort to develop an insecticidal spray to replace pyrethrum dusts in tobacco warehouses. In 1941, experi- ments were begun under industrial conditions to develop methods of applying suchsprays in warehouses. To be effective, a contact spray had to be distributed throughout the en- tire air space of the building. This posed a difficult problem, as the insecticidal mist had to be driven from 50 to 100 feet over the hogsheads of tobacco racked 3 tiers (over 10 feet) high. Equipment was developed which would do this, and some results of such treatments have been published in various papers (3, 4, 5, 6, 7, 8, 9, 10, 11).
2 Underlined numbers in parenthesis refer to items in Literature Cited, p. 18.
27a
Following World War II (about 1945-1946), high-capacity generators became avail- able for producing thermal aerosols, and shortly thereafter other equipment was intro- duced that produced mechanically formed aerosols. From about 1947 to 1955, extensive research was conducted with oil-based mists and aerosols. The results of much of this research have not been published previously.
ADVANTAGES OF PYRETHRUM
Pyrethrum is one of the safest insecticides known. It is toxic to insects, but has a very low toxicity to man. There is an occasional individual who is allergic to it, but in nearly 20 years of experimental work and more than 15 years of industrial use in tobacco warehouses, no instance is known of injurious effect to applicators or laborers intreated buildings. Applications as often as 6 days a week for 7 months have not injured flue- cured tobacco in hogsheads. Spillage of liquid insecticide may taint tobacco, but this rarely occurs except under unusual circumstances. Nevertheless, it is considered un- desirable to apply spray or aerosol directly to uncovered tobacco, in order to avoid even the most remote possibility of taint on account of dripping or excessive dosage.
Other contact insecticides may be as effective as pyrethrum in killing the tobacco moth or the cigarette beetle. Some have been used to a limited extent, particularly lin- dane (12). No other contact insecticide tested up until this time, however, has been found to be more effective as a killing agent against these insects. Some are cheaper, but to offset that advantage they are much more dangerous to use.
The use of oil-based pyrethrum insecticides in tobacco warehouses has been approved by fire insurance underwriters, if recommended precautions are followed.
The question is sometimes raised whether the cigarette beetle will develop resist- ance to pyrethrum, since many insects have developed resistance to the new chlorinated hydrocarbon and the phosphate insecticides. To date no such resistance has been ob- served.
DIFFERENCE BETWEEN SPRAYS, MISTS, AND AEROSOLS
The layman often thinks of the terms ''spray" and ''aerosol'' as synonymous. How- ever, there is a real difference. An aerosol is defined as a suspension in the air of particles none of which have a diameter greater than 50 microns. A mist is not as finely atomized as an aerosol and has droplets of 50 to 100 microns in diameter. A fine spray has droplets of 100 to 400 microns in diameter. An insecticidal aerosol has par- ticles with diameters ranging from 1 to 50 microns (1/25, 400 to 50/25, 400 inch) (13). However, in most aerosols produced under industrial conditions, a few of the particles, 1 to 2 percent, may have diameters in excess of 50 microns.
In a mist used in tobacco warehouses, such as is described in this paper, approxi- mately 75 percent of the droplets range from 5 to 50 microns in diameter, and 25 percent are in excess of 50 microns. Therefore, the treatment is a mixture of a mist and an aerosol.
Because of the larger droplets in a mist, this form of application is especially well adapted to use in open-type warehouses or sheds, where air currents sweeping through such buildings would carry out an aerosol almost as fast as it was introduced (fig. 1). On the other hand, with an electric mist blower operated from the central aisle of the ware- house, a mist may be blown over the entire building, and reasonably good distribution obtained.
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BN-7618
Figure 2. --Semiclosed type of tobacco warehouse.
At one time, dataseemed to indicate that the larger droplets of a mist were more ef- fective than the smaller droplets of an aerosol against the cigarette beetle. This was later disproved, and it was shown that the smaller droplets were just as effective as the larger (table 1). Consequently, in closed buildings (fig. 2), where air currents do not \dissipate the aerosols, they can be used to advantage. The finer droplets of an aerosol vhang in the air for a much longer time and often facilitate better distribution. However, ithe heavier droplets of insecticide produced by a mist blower operated from the aisle ‘within a warehouse may be blown against a light breeze to better advantage than an ‘aerosol. For the foregoing reasons, mists can be used efficiently in open sheds (figs.
3 and 4), but aerosols cannot. Either mists or aerosols can be used in closed buildings, but, as a rule, better coverage can be obtained with an aerosol. However, there are limitations on the use of aerosols. Thermal aerosols are produced by heat, and in most of the commonly used generators the source of heat is a gasoline flame, burning ina combustion chamber. Because of the fire hazard involved, fire insurance underwriters have banned taking such machines into tobacco warehouses. Consequently, the aerosol is usually blown into a warehouse through an open door (fig. 5). Some machines for “making mechanically produced aerosols do not have this disadvantage.
| In large warehouses when the aerosol must be introduced through a door it is often difficult to get satisfactory distribution. The blast of aerosol from the generator can be delivered in only one direction, which is usually down the central aisle. The walls of -hogsheads on either side of the aisle tend to channel the aerosol and interfere with its movement over and between the hogsheads. This distribution is further complicated by certain methods of storing tobacco. If the hogsheads are so racked that there is only
a little free space between the tops of the hogsheads and the ceiling (fig. 6), distribution of an aerosol is handicapped. This may be complicated further by the large mains of a sprinkler system partially blocking the head space above the hogsheads. If such pipes are filled with cold water, the aerosol may condense on the pipes and drip on the hogs- heads below. In at least one known instance, such a drip was enough to taint a small amount of tobacco in the top hogsheads.
Some tobacco companies have 2- or 3-story warehouses, and getting the aerosol into the upper stories of such buildings is a problem. This difficulty has been solved in part by the use of large, permanently installed pipes, such as are shown in figures 7 and 8,
OIL DILUENTS
Oil-based sprays are usually more effective than water-based emulsions. More- over, tobacco is almost hygroscopic, and excess moisture favors the development of rots and molds. Because of this, the use of oil-based insecticides was deemed more practical in tobacco warehouses. In Great Britain, a heavy oil has been used as the solvent in pyrethrum sprays (2) with certain advantages. However, heavy oils leave an objectionable greasy deposit in tobacco warehouses. Consequently, in these studies a highly refined, very volatile hydrocarbon oil was used. Specifications for such oil are:
Specific gravity at 60°F. 0.77 - 0.80 Flash point (Tag closed cup) °F. 140 minimum Initial boiling point °F. 160 - 170 preferable Distillation end point °F. (370 minimum) (490 maximum) Unsulfonated residue 97% minimum Color Water white Odor Neutral, no kerosene or
naphtha odor, no resi- dual odor.
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BN-4595 Figure 3. --Mobile power space sprayer especially designed for use in tobacco warehouses.
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Figure 4. --Aerosol escaping from an open shed type of tobacco warehouse.
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Figure 6. --Interior view of tobacco warehouse showing the lack of head room between hogs- heads and ceiling.
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Oils of this type have proved quite satisfactory (14). Some of the oils on the Ameri- can market that meet these specifications are suitable for use in tobacco warehouses, whereas others are unsuitable, because they leave a greasy deposit. Many tobacco firms have had experience with a specific oil that they have found to be suitable. How- ever, if a firm has had no experience with a specific oil, it is suggested that it make small-scale tests with the oil before using it in a tobacco warehouse.
SYNERGISTS
Because of the high price of pyrethrum, the use of synergists, or activators, as additives to insecticides has become widespread. Such materials are highly effective against many insects, especially house flies and mosquitoes. Many people cannot seem to understand why an insecticide may be highly effective against one insect and almost completely ineffective against another. Yet this is often true. They would not expect the same medicine to be equally effective against different disease organisms. However, in tests made of synergists for pyrethrum, none has been found sufficiently effective as a contact insecticide against the cigarette beetle to justify its use. Two of the most com- monly used synergists, piperonyl butoxide and sulfoxide of isosafrole, have been widely tested. Both are slightly effective against the tobacco moth, but are of little advantage against the cigarette beetle (table 2). Neither one is objectionable in a spray formula for use in tobacco warehouses, but they should not be substituted for the pyrethrins content of the insecticide. For the cigarette beetle, it has been demonstrated repeatedly that the effectiveness of a pyrethrum spray is closely correlated with the amount of pyrethrum it contains.
CONCENTRATION AND DOSAGE
For maximum effectiveness, a contact insecticide is primarily dependent upon two factors--hitting the insects (1) with the spray particles and (2) with a lethal concentra- tion of the insecticide. To obtain insecticidal contact with all the insects in the air space of the warehouse, itis obviously necessary to fill the air space with an insecti- cidal mist. The volume of liquid insecticide required to accomplish this is partly dependent upon the fineness of atomization--droplet size--and the method of disper- sion. In open sheds, when a mobile mist blower can be moved up and down the central aisle to dispense an insecticide, a volume of 3 fluid ounces (approximately 100 ml. per 1,000 cubic feet of air space) has been found adequate to fill the air with mist. More than this volume of liquid was not needed and appreciably less failed to give satisfactory coverage. In closed buildings, when an aerosol is used, a volume of 2-1/4 fluid ounces (75 ml.) per 1,000 cubic feet of air space has been found sufficient to fill the building.
The killing power of a pyrethrum insecticide is primarily dependent upon its total pyrethrins content regardless of its dilution (pyrethrins are the active principle of pyrethrum). In other words, whenthe pyrethrins content is the same, a small amount of a concentrated spray may be as effective as a large amount of diluted insecticide. The mortality of the tobacco moth and of the cigarette beetle produced by a given vol- ume and concentration of pyrethrum oil has been worked out under controlled conditions and is shown in figures 9 and 10. It will be noted that when plotted on logarithmic paper, the curves produced are straight lines. At a dosage of 100 ml. per 1,000 cubic feet, a concentration of 0.2 percent pyrethrins was required to give approximately 100 percent mortality of the tobacco moth (fig. 9). At the same dosage rate, 0.1 percent pyrethrins gave 95 percent mortality, 0.05 percent pyrethrins gave 90 percent, and 0.025 percent pyrethrins gave 75 percent. However, at a dosage rate of 200 ml. per 1,000 cubic feet, a concentration of 0.1 percent pyrethrins gave 99.5 percent mortality, and at a dosage rate of 50 ml. per 1,000 cubic feet, 0.2 percent pyrethrins gave 97 percent mortality of moths. It is essential, therefore, that an adequate concentration of insecticide be used to give high kills, and that an adequate volume of liquid be used to give satisfactory distribution.
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thermal aerosols.
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Figure 7. --Multistory tobacco warehouses with permanently installed pipes for the introduction of
BN-5261
Figure 8. --Introducing a thermal aerosol into the second story of a tobacco warehouse through a
permanently installed pipe.
MORTALITY OF TOBACCO MOTHS IN RELATION TO DOSAGE OF PYRETHRUM IN SPRAY
COC ee
t + |
99.5 | 99.0 |
98.0 95.0
90.0 |
80.0 +-—
70.0 | 60.0 t 50.0
40.0 30.0 ; 20.0 r T [ iil —
10.0
30 40 50 150 200 300 (in ml.per |,00O cu.ft.; percentages on curves indicate concentration of pyrethrins )
NEG. NO. 6974 -59 (1) AGRICULTURAL MARKETING SERVICE
U.S. DEPARTMENT OF AGRICULTURE
Figure 9.
MORTALITY OF CIGARETTE BEETLES IN RELATION
300 (in ml.per!,000 cu.ft.; percentages on curves indicate concentration of pyrethrins)
U.S. DEPARTMENT OF AGRICULTURE NEG. NO. 6975-59 (1) AGRICULTURAL MARKETING SERVICE
Figure 10.
10 -
As stated previously, the cigarette beetle is much more resistant to pyrethrum than is the moth. At a dosage rate of 100 ml. per 1,000 cubic feet, a concentration of 1.0 percent pyrethrins killed 93 percent of the cigarette beetles (fig. 10). At the same con- centration, a dosage rate of 75 ml. per 1,000 cubic feet killed 86 percent, and 50 ml. killed 70 percent. A concentration of 0.75 percent pyrethrins at a dosage rate of 100 ml. per 1,000 cubic feet killed 80 percent; at 75 ml., 70 percent; and at 50 ml., 45 percent.
SUBLETHAL EFFECT OF PYRETHRUM ON CIGARETTE BEETLES
The effect of pyrethrum upon the cigarette beetle is not entirely limited to its killing power. There is an additional dividend from its use which is not readily apparent. It has been found that beetles exposed to a sublethal dosage of pyrethrum (beetles that were not killed and apparently recovered completely) deposited only half as many eggs as beetles not exposed to the insecticide (7). Thus, a space spray or aerosol that kills 93 percent of the beetles has a practical control value of approximately 96-97 percent, because the surviving beetles lay only half as many eggs as they would normally.
FREQUENCY OF APPLICATION
Two of the factors limiting the effectiveness of mists and aerosols are the acces- sibility of the insects to the insecticide and the rapidity with which eggs are deposited. The tobacco moth has to emerge from the tobacco in order to mate and lay eggs. There- fore, all of the moths become accessible to the spray. Furthermore, the moth does not deposit eggs as soon after emergence as does the cigarette beetle. Consequently, weekly applications of pyrethrum have been found to give excellent control of the moth. The progressive buildup of a tobacco moth population in a tobacco warehouse after one application of spray, as indicated by suction-light trap records, is shown in figure ll.
In contrast to the tobacco moth, the cigarette beetle does not have to emerge from the tobacco in order to mate, and an appreciable percentage of the beetles infesting tobacco will mate and continue to breed without ever coming out of the tobacco. This percentage. increases with the intensity and age of the infestation. With tobacco in stor- age for 3 years or longer, the percentage of beetles not emerging may exceed 1/3 of the total population. However, the beetles that do emerge usually begin laying within 24 hours after emergence, and 66 percent of all eggs are deposited within 4 days after emergence. Because of these factors, control of the beetle by means of mists or aerosols is very difficult; in heavy infestations of old tobacco, itis impossible. Under such conditions even daily applications of aerosol 6 days a week have failed to give control. The best that can be anticipated from frequent applications is to reduce the potential beetle population increase, and retard the development of the infestation.
No definite rule can be offered for the optimum frequency of application of sprays or aerosols for the cigarette beetle. For light infestations in tobacco stored for only a short time, once a week may be sufficient. In heavier, older infestations, the frequency may be increased to advantage. The number of applications will have to be determined in each instance on the basis of economics. If valuable tobacco becomes heavily in- fested, and no more efficient means of insect control is available, daily applications may be desirable. Usually, however, 2 to 3 applications a week are as many as can
be economically justified.
TIME OF APPLICATION
Studies of the habits of the cigarette beetle have indicated that approximately 85 percent of the beetles are actively flying in a tobacco warehouse between 5 p. m. and midnight. Between 8 a. m. and 5 p. m. (the usual working day) less than 25 percent are active (10). For this reason, mists or aerosols applied between 5 p. m. and midnight give the best results.
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BUILD-UP OF TOBACCO MOTHS IN WAREHOUSE AFTER ONE APPLICATION OF PYRETHRUM SPACE SPRAY
Tobacco moths
6 iG Days after spraying
U.S DEPARTMENT OF AGRICULTURE
Figure 11.
TRAP CATCHES OF TOBACCO MOTHS IN MODERATELY INFESTED WAREHOUSES OF FLUE-CURED TOBACCO
8 houses treated weekly with 0.2 % pyrethrins and 8 untreated Tobacco
moths
3,000
| Untreated a
\- Dusted
23 20 4 18 August September October NEG. NO. 6977-59 (1) AGRICULTU
RAL MARKETING SERVICE Figure 12.
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TECHNIQUE OF APPLICATION
Most of the cigarette beetles flying in a tobacco warehouse are concentrated in the upper areas of the building. In a warehouse with a ceiling 15 to 16 feet high, approxi- mately 3 percent of the beetles caught were taken in traps at the 1-foot level above the floor, 22 percent at the 6- to 7-foot level, and 75 percent at the 12-foot level. There- fore, when applying a contact insecticide to control this insect, it is important to con- centrate on filling the air space above the hogsheads.
On the other hand, the tobacco moth is usually rather evenly distributed at all heights in the air space. If a large number of moths are present, therefore, it is de- sirable to pay more attention to the narrow areas between the rows of hogsheads. When applying a mist from the central aisle of a tobacco warehouse, remember that several seconds are required for the insecticide to travel the length of the hogshead rows. Move the machine slowly and pause opposite the narrow openings between the rows.
When introducing a thermal aerosol into a warehouse, direct the aerosol slightly upward along the aisle, and take care to see that enough insecticide is used to fill the entire air space to the back walls of the building.
EFFECTIVENESS OF PYRETHRUM MISTS AND AEROSOLS Against the Tobacco Moth
Extensive experiments over 14 years have shown that weekly applications of 0.2 percent pyrethrins in an oil solution, applied as either a mist or an aerosol, will effec- tively control the tobacco moth. In fact, where used systematically, the treatment has eliminated the moth as an economic problem.
The effectiveness of weekly applications of a mist containing 0.2 percent pyrethrins applied at a rate of 100 ml. per 1,000 cu. ft. and of a dust containing 0.8 percent pyre- thrins applied at a rate of 3 oz. per 1,000 cu. ft. is compared in figure 12. Within 2 weeks after the start of spraying, the weekly trap catch of tobacco moths dropped below the arbitrary danger line of 50 moths a week, and remained below that line the entire summer, except for 3 weeks when it rose slightly above it. Dusting also gave reason- able control of the moth, although not as good as the mist.
The relative effectiveness of weekly applications of pyrethrum mist and of 2 ware- house fumigations with HCN against the tobacco moth is shown in figure 13. The spray- ing was much more effective against the moth than the 2 fumigations.
In other tests with thermal aerosols, moths’were almost exterminated in the test warehouses, and not enough moths could be found to record.
Against the Cigarette Beetle
Control of the cigarette beetle with mists and aerosols has not been too satisfactory. As can be seen in figure 14, in moderately infested warehouses, a weekly application of pyrethrum mist was approximately as effective as 2 fumigations with HCN. However, neither fumigation nor sprays gave satisfactory control. Figure 15 shows that in heavily infested warehouses, weekly applications of pyrethrum mist were not as effective as 3 fumigations with HCN.
In many tests, treatments with a thermal aerosol have been less effective than treatments with a mist. However, this has not been due to the form of application itself. As shown in table 3, in a series of replicated tests in large warehouses, an aerosol containing 1 percent pyrethrins gave an average mortality of caged cigarette beetles of
ie ys
TRAP CATCHES OF TOBACCO MOTHS IN SPRAYED AND FUMIGATED WAREHOUSES OF FLUE- CURED TOBACCO
| group treated weekly with 0.2% pyrethrins and | group fumigated twice with HCN, IIb. per 1,000 cu. ft.
Tobacco moths
3,000
Fumigated
mo = => o = a ” wo pe) — = oS _— (Sp)
Fumigated
SS
Fumigation =
\7 15 10 Th 4 18 2 16 April May July August September October U.S. DEPARTMENT OF AGRICULTURE NEG. NO. 6978-59 (1) AGRICULTURAL MARKETING SERVICE
Fipure to.
only 56 to 60 percent. Yet, at certain locations in the warehouses where heavy con- centrations of aerosol were obtained, the average mortality was up to 98 percent. In almost every test, complete mortality was obtained at one or more locations. Evi- dently, therefore, low effectiveness could not be attributed to lack of killing power, and it seemed to be due to inadequate distribution. This was corroborated by the results shown in figure 16. The deposit of aerosol on coated, glass microscope slides was closely correlated with mortality of cigarette beetles in that area of the warehouse.
In smaller warehouses of Turkish tobacco where better distribution of aerosol was obtained, the mortality of test beetles was also higher. Table 4 gives the results ob- tained in such warehouses with 3 insecticide formulations, all containing 0.75 percent pyrethrins, and 2 containing the synergist piperonyl butoxide. The average mortality of insects in all the tests ranged from 84 to 100 percent and the averages for the 3 treat- ments were 92, 96, and 97 percent, respectively. Kill of beetles approached perfection in all tests, and there was no significant difference in effectiveness between the 3 for- mulations. Yet, in spite of the high mortality obtained in this experiment, control of the cigarette beetle was not satisfactory (table 5). Weekly applications were started the second week in May, as soon as the beetles became active, and continued for ap- proximately 5 months until the cool weather began. The beetle infestation was not homogeneous in the 5 warehouses, but in each building, as many or more beetles were present late in the season as were found early in the season. The infestation was not reduced by the treatment.
Paine
UNITED STATES DEPARTMENT OF AGRICULTURE Washington, D.C. September 1959 In Marketing Research Report 334, "Pyrethrum Mists and Aerosols for Control of Insects in Tobacco Warehouses," the following page should be substituted for page 15 as it appears in the publication:
TRAP CATCHES OF CIGARETTE BEETLES IN MODERATELY INFESTED WAREHOUSES OF FLUE-CURED TOBACCO TREATED WITH PYRETHRINS AND HCN
I8houses treated weekly with 1° pyrethrins and 17 fumigated twice with HCN, IIb. per 1,000 cu.ft. Cigarette beetles
5,000
Fumigated
4,000
Fumigated
Fumigation -% /
30 13 21 ine) 24 8 22 6 20 August September October November NEG. NO. 6979-59 (1) AGRICULTURAL MARKETING SERVICE
U S. DEPARTMENT OF AGRICULTURE
Figure 14
TRAP CATCHES OF CIGARETTE BEETLES IN HEAVILY INFESTED WAREHOUSES OF FLUE - CURED TOBACCO
4 houses treated weekly with |°%pyrethrins and 4 fumigated 3times with HCN, | lb.per |,000 cu.ft.
Cigarette beetles 4 Z\ x A
\
\ yee y
100,000
80,000
\ 60,000 - x
\ I ° ° \ i en x
24 16 20 «414 28 June July August September October
Figure 15. (Note: In fig. 12, page 12, the subheading now reads: "8 houses treated weekly
with 0.2% pyrethrins and 8 untreated." It should read: "8 houses treated weekly
with spray containing 0.2% pyrethrins, § dusted with powder containing 0.8% pyrethrins, and § untreated."
15
eae dete,
TRAP CATCHES OF CIGARETTE BEETLES IN MODERATELY INFESTED WAREHOUSES OF FLUE-CURED TOBACCO | TREATED WITH PYRETHRINS AND HCN
[8 houses treated weekly with 1% pyrethrins and |7 fumigated twice with HCN, | lb. per 1.000 cuff. Cigarette
beetles
100,000 i, — - / Space spray
80,000 i = —
60,000
30,000
13 24 5 19 16 14 May June July August September October U S. DEPARTMENT OF AGRICULTURE
NEG. NO. 6979-59 (1) AGRICULTURAL MARKETING SESv.cE
Figure 14
TRAP CATCHES OF CIGARETTE BEETLES IN HEAVILY INFESTED WAREHOUSES OF FLUE - CURED TOBACCO
4 houses treated weekly with 1° pyrethrins and 4 fumigated 3times with HCN, | lb.per |,000 cu.ft.
Cigarette beetles
5,000
Fumigated
4000
Fumigated
Fumigation. .-% / \ \
3,000
3 an enLOe ees 8 22 20 June August September October November
US DEPARTMENT OF AGRICULTURE NEG. NO. 6980 - 59 (1) AGRIGULT!IRAL MARKETING SERVICE
Figure 15.
wiiapic
MOVEMENT OF THERMAL AEROSOL IN TOBACCO WAREHOUSE
Floor plan of a tobacco warehouse I70 x I41 2 feet, showing movement of a thermal aerosol after introduction through a door.
Open figures indicate percent coverage by aerosol on glass microscope slides exposed at |2 locations.Encircled figures indicate percent mortality of caged cigarette beetles at 8 of the locations.
U.S DEPARTMENT OF AGRICULTURE NEG NO. 6981-59 (1) AGRICULTURAL MARKETING SERVICE
Figure 16.
CORRELATION BETWEEN TEMPERATURE AND MORTALITY OF CIGARETTE BEETLES FROM A PYRETHRUM THERMAL AEROSOL
Percent Warehouse Mortality Temp °F 80
Mortality of checks
916° 23.30 7 14: 21 2847118225429) 516).23.30'6 I3) 20:27, Slonim e4nleSmlonec April May June July August September October
US DEPARTMENT OF AGRICULTURE NES NO. 6982-5% (i) AGRICULTURAL MARKETING SERVICE
EFFECT OF TEMPERATURE
There is some evidence that the relative effectiveness of a pyrethrum thermal aerosol decreases with higher midsummer temperatures. In one large-scale experi- ment covering a summer season of 7 months, such a correlation was demonstrated.
In figure 17, the relation between mortality of caged test insects and temperature is clearly shown. In this experiment, the mortality of the checks (untreated insects) ac- tually increased with higher temperatures, while the mortality of test insects decreased,
Under some conditions, the very high temperatures produced in the combustion chamber of a thermal aerosol machine may cause a slight breakdown of the pyrethrum. Some indication of this has been observed, but although considerable effort was expended attempting to prove or disprove this, the results were inconclusive.
= dkyp =
i tts ol ee
LITERATURE CITED
(1) Back, E. A., and Reed, W. D. 1930. Ephestia elutella, Hubner, a new pest of cured tobacco in the United States. Jour. Econ. Ent. 23: 1004-1006.
(2) Potter, C. ; 1935. An account of the constitution and use of an atomized white oil pyrethrum
fluid to control Plodia interpunctella (Hbn.) and Ephestia elutella (Hbn. ) in warehouses. Ann. Appl. Biol. 22: 769-805.
(3) Reed, W. D., and Vinzant, J. P. 1942. Control of insects attacking stored tobacco and tobacco products. U. S. Dept. Agr. Cir. 635, 44 pp., illus.
(4) Tenhet, Joseph N. 1945. Laboratory tests of insecticides for the tobacco moth and the cigarette beetle. Jour. Econ. Ent. 38: 449-451.
(5) 1946. A power sprayer for applying concentrated insecticides. U. S. Bur. Ent. and Plant Quar. ET-231, 4 pp., illus. (Processed)
(G))- citadeeiees 1947. Pyrethrum oil sprays in open type tobacco warehouses. U. S. Bur. Ent. and Plant Quar. E-717, 5 pp. (Processed)
(0) Sateeetoe ieee 1947. Effect of sublethal dosages of pyrethrum on oviposition of the cigarette beetle. Jour. Econ. Ent. 40: 910-911.
\) ae eee 1949. Control of insects in stored tobacco with pyrethrum-oil. U. S. Bur. Ent. and Plant Quar. EC-9, 8 pp., illus. (Processed)
(2)) eee 1949. Experiments with pyrethrum oil sprays for control of the tobacco moth and cigarette beetle. U. S. Bur. Ent. and Plant Quar. E-791, 12 pp.
| |
(Processed). (10)> 12 ee, 1955. Timing of sprays to control the cigarette beetle. U. S. Dept. Agr. AMS-49, 6 pp. (Processed) (11) , and Bare, C. O. 1951. Control of insects in stored and manufactured tobacco. U. S. Dept. Agr. Gir. 869, 32 pp., illus. (12) , and
1952. Lindane as an insecticide to control the tobacco moth and the cigarette : beetle. Jour. Econ. Ent. 45: 218.
(13) United States Department of Agriculture 1952. Insects. U. S. Dept. Agr. Yearbook. 780 pp., illus.
(14)
1955. Oil base for insecticide sprays in tobacco warehouses. U. S. Dept. Agr., Agr. Mktg. Serv., Stored-Product Insects Section (Processed; unnumbered).
Seiler
TABLE 1.--Effect of droplet size in a mechanically produced oil-based pyrethrum aerosol on mortality of the cigarette beetle
Droplets with diameters less than--
Mass median Maximum Mortality diameter diameter of of uncaged of droplets droplets beetles
Percent Percent Percent
Microns Percent
- - - - - - 92 25 1B 85 98 = 50 100 8 45 64 80 90 100 89 1 20 40 65 iE 150 100
| Controls (un- treated)
replicated laboratory tests
Concentration of insecticides Mortality Treatment
} : Piperonyl Tobacco Cigarette SSS ree butoxide Sulfoxide moths beetles
_ TABLE 2.--Mortality of tobacco moths and cigarette beetles exposed to pyrethrum aerosols in ¥ | |
Percent Percent Percent = Percent Percent Pyrethrum in oil...... Soe 0.025 86 28 05 85 19 z Gal 96 20 ; ae 100 42 ys 100 38 | 52) 100 36 iL 100 1) ALA) 100 oh} Controls (untreated)... 9 4 Pyrethrum-piperonyl DUGORUG STM Ol s.. a.s aves 0 5 olOisnivs 0.314 100 18 -063 363 100 2 212) 2D 100 De 418 4.18 100 30 627 Geen 100 74 89 8.9 100 84 Controls (untreated)... 8 2 Pyrethrum-sulfoxide of SOSA LOGS TM, Ol diss sce -0388 0.3113 89 27 OVE sO2e> 94 42 2155 We245 99 43 jouk 2eA9 98 45 =02 4.98 100 61 Controls (untreated)... ale 10
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TABLE 5.--Weekly trap catches of cigarette beetles in 5 warehouses of Turkish tobacco treated weekly with pyrethrum aerosols containing 0.75 percent of pyrethrins
Beetles trapped Pyrethrum in Pyrethrum-piperonyl oil butoxide in oil ee 7 7-A
Pyrethrum-piperonyl butoxide- tetrachloroethylene in oil
Warehouse 6-A
Warehouse 8-A
Number Number Number Number Number
VERS oC aan eee 30 25 1 0 0 ANG aretagerccc 0 O 0 0 0
DB otelest 13 8 12 15 20 Shite aerate 46 110 39 oF 20 BitiTIgw Get tetetot So 72 a3 76 66 18 Daye Neva cee ie 148 126 108 140 31
DO atereres elove ce 650 800 675 1,450 300
Pils eeceveeececece ALY ASS 200 225 850 PIES) Jighiki; 10 ea a ee 50 8 21 23 13 a ree evareate 24 18 36 42 bys Dee cate ai 37 51 Ae) 28 68
ING ASS SSSI 1,500 625 6,500 650 1,000 SRE IG ots, occ 3,400 700 2,000 675 500
DD RCN ts 2,000 55 3,330 330 350
DOM yo ete. 1,050 300 2,000 200 325
SS pitcesOs vaste ste. ore 1,300 150 1,000 63 100 Doe creee POO 110 95 29 150
INQN Te fava Sheree 1,100 Ws 150 We 1,400
DG erie tes 1,300 1,300 18 330 1,300
Otte JE aCe ae 333 29 16 58 39 Moibaillastacis tices te 15,928 oy ox. 16,349 4,990 5,963
+ Count over 2-week period. 2 Count not available for first week in August.
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