f 7.±i LAft No. 112. I iiitcil Stat( 0\Uj F V o^ ■ >anment of Agriculture, Ot* KNTOMOUOGY, ARD. Entomologist and Chief of 1 CONTROL OF THE MEDITERRANEAN FLOUR MOTH BY HYDROCYANIC-ACID <;AS FUMIGATION. Bj I II « mil i \i'i s. Si 1 1 . In Char ' Crop and Stored Prodv I vi i;< >i>i ( i OBI . Until in Bomewhat recent years Qour mills in the United States were little troubled with injurious insects. It is true thai weevils and other granary pests were brought into the mills with grain, and in tlic course of time many mills have become infested with Qour beetles Beginning with the year 1892, however, several Cali- FM 1 MwUfTllWll fllHIl lllllttl ( ITjltl»ffcl tmtntlffn) a. Moth;'). same from oflana. id Knlaro"! r moriM-n!. thor's Illustration.) PIG -' M.'.liicrrancan Hour moth: i dorsal Haw. (Au- thor's i ll< i fornia mills became infested by the Mediterranean Hour moth (Ephettia kuehirieUa Zell.), which has been aptly called "the scourge of t he Hour mill " and t he " winged gray plague." At first its prog] in this country was slow, hut in lees than a decade it had become recognized as a most Berious pest in many States, and at the present time it is known to occur in practically all of om- principal milling centers, and in most of our States from the Atlantic to the Pacific and from Canada to Mexico. " Chiefly speciec ol Tribolium, Ctenocori Cir ii-_>— 10 1 DEPC Descriptive. — The adult insect is a phycitid moth with a wing expanse of a little less than an inch; the fore-wings are pale leaden gray, with transverse black markings of the pattern shown in the accompanying illustration (fig. 1, a); the hind-wings are dirty whitish, semitransparent, and with a darker border. The larva or caterpillar, illustrated at figure 1, c, ( , and at figure 2, is whitish with minute black dots, and sparsely hairy. When full grown it measures' about one-half an inch or a little longer (12.5-17.5 mm.). The chrysalis, shown at figure 1, d, is reddish brown. Distribution. — Until the year 1S77, when the moth was discovered in a flour mill in Germany, this insect was comparatively unknown. Later it invaded Belgium and Holland, and in 1886 appeared in England. Three years afterwards it made its appearance in destruc- tive numbers in Canada. In 1892 it was reported injurious in mills in California, and in 1895 in New York and Pennsylvania. From that time forward until 1904 the dissemination of the species was comparatively slow. In 1898 it had reached Minnesota, the next year Wisconsin; in 1900 it had greatly increased in Minnesota: two years later it invaded Michigan, and by 1904 it was reported in several other States, including Indiana, Illinois, Montana, Colorado, Ohio, and Iowa. In later times, each year has witnessed a similar increase in distribution, until now, in 1910, this flour moth is attract- ing more attention than any insect that ever infested mills or other buildings where cereals are stored; indeed, it is almost the sole topic of complaint of millers at the present writing, correspondence in regard to weevils and flour beetles, which was at one time heavy, having fallen off very noticeably. Ravages and habits. — The caterpillars form cylindrical silken tubes in which they feed, and it is largely due to their habit of web spinning that they are so injurious where they obtain a foothold. Upon attaining full growth the caterpillar leaves its original silken domi- cile and forms a new web, which becomes a cocoon, in which it undergoes transformations to pupa and to imago. While searching for a place for transformation the insect is most troublesome. The infested flour becomes felted together and lumpy, the machinery becomes clogged, necessitating frequent and prolonged stoppage, and resulting in a short time, in large establishments, in the loss of thou- sands of dollars. A sample of matted flour is illustrated in figure 3, from a photograph by Mr. C. H. Popenoe. As to the losses caused directly and indirectly by this insect it has been difficult to obtain estimates, the lowest being between $100 and $200 to a mill of 1,000 barrels capacity. The average loss due to closing down the mill and cost of treatment seems to be not far from $500 for each fumigation, ''to say nothing of the loss to busi- ness," according to one Kansas milling firm. An estimate of $1,000 [Cir. 112] for two fumigations can oof be far from right, although others esti- mate SJ, t, while »\\\\ others n« QeTS of larger mills claim it to be 15,000 a year. One prominent miller states thai , aside from the cost \2 ^^W Mm LiBfc ft**3M * > '? 1 ''^B PWa\l ' *«HI T .<■ « *( ^a. ^^Br t - H* ^iiiiiiife. ^B 1 Flo. 3- Mattel flour showing the work of the Mediterranean flour moth. (Original.) of fumigating, the loss due to Btoppage w bile cleaning is incalculable, ami expresses the opinion that some restrictions should be imposed on millers who tlo not clean and fumigate their mills. [Or. IIS] Although thr Larva prefers Hour or meal, it will attack grain when the former are not available, and it flourishes also on bran and pre- pared eereal foods, including buckwheat, grits, and crackers. It lives also in the nests of bumblebees and in the hives of the honey bee. FIRST USE OF HYDROCYANIC-ACID GAS AGAINST INSECTS IN STORED PRODUCTS. The use of hydrocyanic-acid gas as a remedy for insects in mills and other inclosures whore grain, flour, and similar products are stored was first suggested by the late "\Y. G. Johnson in the American Miller for March, 1898, the incentive for its employment having been an invasion of cockroaches in a mill in North Carolina. The first test of this method as a means of destroying insects in stored products was probably that made by the writer the same year. Additional experiments were soon afterwards made in conjunction with Mr. Pratt and the cost and the advantages and disadvantages carefully weighed, with the resulting conclusion that since hydrocy- anic-acid gas is infinitely more dangerous to human life than bisulphid of carbon, as well as more expensive, its employment as a fumigant for ordinary insects injurious to stored products was less desirable. On this account no publication was made of the results nor was it, until recently, recommended to the numerous persons who inquired for remedies for mill pests. Soon after this first experiment a test to determine the availability of this gas against the Angoumois grain moth was made on a larger scale but with very imperfect success. 6 a March 5, 1898, the writer, with Mr. F. C. Pratt, then working under his direc- tion, fumigated a lot of dried grain infested by the rice weevil (Calandra oryza L.) and a leguminous seed affected by a Bruchus or seed weevil, the material being placed in a moderately tight fumigating box. The cyanid of potash was purchased in open market and was used at the rate of 2 ounces to each 100 cubic feet. A quantity of acid slightly in excess of the salt was employed with twice that amount of water. The experiment began at 4 p. m. Saturday and was conducted in a building in which the temperature was usually from 70° to 76° F. The following Monday morning at 7.30, when the door was opened for airing, no odor was perceptible, and only a very slight trace of gas could be detected a half hour later when the box lid was removed. As a result all the seed weevils (Bruchus) loose in bags were found dead and all of the rice weevil, except a very few individuals, which revived after a few hours — less than 0.1 per cent — were killed. *> A lot of paddy or unhulled rice infested by this moth was desired to be fumigated and was placed in what appeared to be a nearly air-tight inclosure, a room specially prepared for the purpose. The cyanid was prepared in the usual way and was used at a strength of about 1 ounce to 100 cubic feet, but after the fumigation the insects were seen to be flying freely about the fumigating room. See Bureau of Entomology Cir. No. 46, entitled, "Hydrocyanic-acid Gas against Household Insects," by L. 0. Howard, first issued in 1902, revised edition February 20, 1907. Note what is said in the footnote on page 2. [Cir. 112] During 1899 mill> were fumigated in Pennsylvania and < >lii", under the direction of Professor Johnson, with Bal isf actor} results, and con tinued in later years b) and under the direction oi Professor Johnson well a> l>\ Professor Washburn, State entomologist of Minnesota, Prof. II \ Surface, State zoologist of Pennsylvania, and other State officials. In the course of time hydrocyanic-acid gas has come to be recognized as the besl fumiganl for the Mediterranean Sour moth. Ii i> equally valuable against related moths found in mills, l>ut i- le~^ effective in destroying flour beetles and grain weevils, and even in the destruction <>f the Angoumois grain moth in corn. Indeed, it is not general!) recommended for any of the latter pests. Prom what subsequently has been learned of tlii- method, failure in some cases was undoubtedly « I im> to impure potassium cyanid and to faulty application of the process, since the fumigating vessels were rather small for the purpose and permitted a considerable boiling over at the t>>p. Much residue also remained; in other words, the potassium cyanid was probablj too weak, perhaps no stronger than .">n to 60 per cent pure, as was also the sulphuric acid, which was not used in sufficient quantity to produce a perfect gas, a considerable amount of cyanid remaining unaffected as solid residue in the generat- ing vessel. It seems also probable thai the cyanid was broken into too line particles, but this detail can not now he remembered. Owing to these failure-- as well as to t hose of other tests which were afterward- made, the suspicion arose that something was wrong with the ingredients. A sample of the cyanid used was submitted to the Bureau of Chemistry and treated with sulphuric acid, with the result that only 54.50 per cent of the amount of hydrocyanic-acid gas demanded by theory was found. Analysis showed 51.70 per cent potassium cyanid. 2.1)7 per cent sodium cyanid. and .'!'.>. 28 per cent potassium carbonate, the remainder consisting of sodium chlo- i id or common salt and impurities. It will be noticed that this cyanid was little more than half a- strong a- demanded for per- fect work; hence, what appeared t" he a fumigation at the rate of 30 ounces t<> 1,000 cubic feet was in reality only about 16 ounc< " An instance oi fumigation with impure cyanid of potash should be cited. During September, 1904, th«' writer, with Mr Pratt, undertook the fumigation of a dwelling infested by thi if cyanid to 100 cubic i' • . which destroyed man} I ties Two weeks later, however, the beetles bad again accumulated in numbers, showing th.it neither larva- nor pups had been killed to an} • rhen 3 ounces of cyanid were used with a still loi .i total of practically forty-two bout killed many larva which dropped from the furniture, the principal -eat of infestation, although carpets were also affected, but many were probably not killed inly the eggs wen destroyed, as the insects continued t.. infesl the house, with the result that bef i third fumigation could !»• given the furniture was disposed of For particulai - :o. Bui. ">i. Bur. But., I S. Dep( Agi . [Or. 112] It should not be imagined that because this method is of value against the Mediterranean flour moth and related insects, and soft- bodied species like psocids or book-lice, which also occur in mills, that it is a sovereign remedy for other insects in mills and other inclosures. Quite the contrary; it has been found only partially effective and therefore unsatisfactory when used against grain weevils, flour beetles, and other hard-bodied insects, and the pre- paratory stages of the Angoumois grain moth, although effective in killing the adults of the latter. Indeed, not until very recent years has its use become generally recommended for the flour moth. Mr. C. H. Popenoe, working under the writer's direction, in fumi- gating primarily for the flour moth, succeeded in killing many of the confused flour beetle (Tribolium confusum Duv.) in two application- at 4 ounces to 1,000 cubic feet. A larger percentage was destroyed by one application at the rate of S ounces, and so on up. Mr. D. K. McMillan had similar good success with 10 ounces. In pamphlets published in 1904 Prof. F. L. Washburn has rec- ommended hydrocyanic-acid gas for the treatment of the flni'- moth, stating the advantages of this treatment and giving details as to the penetrating power of the gas and other matters. As an instance of the successful use of hydrocyanic-acid gas, the experience of a Kentucky milling firm that was advised to use this method of fumigation may be briefly narrated. In the city where this firm is located the species had been present in their mill four years, yet a few months prior to hearing from them the writer did not know of the insects' occurrence in that State. It had been introduced in second-hand machinery. Bisulphid of carbon had been used by them previous to their correspondence with the writer and was described as "no good except for weevils in stored grain." It had been employed at the rate of 300 pounds to 62,400 cubic feet of air space, or about 5 pounds to 1,000 cubic feet — fully twice as strong as necessary in an ordinary mill. Afterwards, by the writer's advice, hydrocyanic-acid gas was employed and the follow- ing report was made, August 24, 1909: Saturday, July 24, 1909, our mill was fumigated with hydrocyanic-acid gap, using 18 4-gallon jars, each charged with 3 pounds (if cyanid of potassium, 4J pounds of sulphuric acid, and 7 pounds of water. We killed moths and their eggs, worms and bugs of all kinds, wasps, mud-daubers, spiders, bats, rats, and mice, and also English sparrows perched outside on the roof. It has just been one month since we fumigated, and we see no more as yet. There is no sense in a miller being pestered with the flour moth. Hydrocyanic-acid gas will kill the moth and the eggB. Our correspondents also wrote that in their opinion it would be difficult to operate any mill infested with the flour moth without a Ninth Annual Report State Entomologist of Minnesota, pp. 31-36, 1904; Special Report State Entomologist of Minnesota, February 29, 1904. [Clr. 112] fumigation, as the cos1 of shutting down, cleaning machinery, etc., would destroj the profit. In this latter fumigation, 54 pounds oyanid of potash were used, equivalent t" 13.9 ounces to 1,000 cubic feet, or aboul one-third more than necessary if the building was tight and the ingredients known to be pure. BUHMAR1 OF VALUE <>i nil. HYDROOTANIO-AOID OAfl METHOD. The special qualities of hydrocyanic-acid <;ns and some of the ad- vantages which it possesses over other insecticides (as well as it- disadvantages) as q fumigant for mills and other buildings infested by insects may be briefly summarized as follows: 1. It is generated without the aid of fire, in which respect there i- a distinct advantage in its use in preference to sulphur fumiga- tion, utiles the Clayton process i- employed. 2. It is practically noninflammable and nonexplosive in a large confined -pace when generated according to methods now in practice. .;. It i- possible, therefore, to use this method of fumigation when' with the employment of cither bisulphid of carhon or Bulphur a con- tlict with insurance companies might occur. I It is not, injurious to cereals or other dried products in storage, either for food or for seed, in which respect it i- superior to sulphur, which destroys the germinating qualities of seeds as well as plant life generally. "). Fumigation may he employed at any time, night or day, but preferably in a moderately warm temperature and on a calm day w ithout wind. 6. In a very short time after ventilation of the treated premises the characteristic "peach-pit" odor of the gas entirely disappears and, properly used, no -olid residue remains in the generator. 7. Hydrocyanic-acid gas is lighter than air and ha- considerable penetrating power — not so great, however, a- possessed by sulphur where forced into buildings and other inclosures by means of the Clayton pro. i - The gas, generated in air-tight inclosures, creates a positively deadly atmosphere, and thus used destroys most Btages of the Hour moth and some other insects. It i- still more deadly at a much shorter exposure to man and other mammals, including domestic animals, rats, mice, and other vermin, than to mill insects. 9. It is tin 1 mosl powerful poison in common use, which fact being fully recognized, human beings are not readily tempted to run unnec- ri>ks of exposure to its deadly fumes. 10. The pre - comparatively inexpensive under conditions which permit of buildings being made nearly gastight, especially when a complete exposure of between l'4 and 36 hour- can he obtained. [Or. 112] CIIEMICALS AND OTHER SUPPLIES. In the fumigation of mills, warehouses, elevators, and other struc- tures and inclosures infested by insects, especially the Mediterranean Hour moth and some other soft-bodied insects, in stored cereals, with hydrocyanic-acid gas two chemicals are used, both poisonous and dangerous to handle. They are cyanid of potassium, called also potassium cyanid and cyanid of potash, of a high grade or chemically pure (98-99 per cent), concentrated sulphuric acid having a specific gravity of about 1.83 or 1.84 (equivalent to 66°Baume), and water. The standard commercial sulphuric acid will answer. Cyanid of potash (KCN or KCy), the first ingredient, is a white crystalline salt, permanent in dry air, but rapidly decomposable or deliquescent in a moist atmosphere, when it gives off an odor of hydrocyanic or prussic acid. It is readily soluble in water, has a bitter taste, and is extremely poisdnous. Sulphuric acid (H 2 S0 4 ), the chemical used in liberating the gas, is so well known as scarcely to require description at this point. It might be well, however, to state that it is known commercially also as oil of vitriol or simply "vitriol," and is a dense, oily-looking fluid, colorless when pure, having when concentrated a specific gravity of about 1.8, and containing about 90 per cent H 2 S0 4 . It is nearly twice as heavy as water, and in action it is powerful, being corrosive to both animal and vegetable substances. Hydrocyanic acid (HCN or HCy), the resultant gas liberated by combining cyanid of potash and sulphuric acid, is one of the most energetic poisons known to science. A single drop of the pure acid placed inside of the eye causes instant death. When taken internally it causes paralysis of the heart, of the respiratory center, and of the vasomotor region of the medulla. The immediate cause of death in most cases is due to obstruction of the respiration or to stoppage of the heart's action. The purity of the cyanid of potash and sulphuric acid to the degree indicated above is essential to the success of fumigation, and efforts should be made to obtain these chemicals through thor- oughly reliable firms, and if there is any doubt as to their strength they should be submitted to analysis. Many of the disappointments and failures in fumigation have come from the employment of impure cyanid of potash or acid below the standard strength. These two agents are, however, now in such common use for fumigation pur- poses that with ordinary care in their purchase there is little risk in this direction. |Cir. Ill'] PR( IPOR1 l«'\ <>i ( IIEMII \l 3. The hydrocyanic-acid gas is produced l>y a combination of cyanic] of potash ami sulphuric acid in water. The most economical and efficient production of the gas, as demonstrated by a recent thorough investigation of the subject by the Bureau of Entomology in coopera- tion with tin 1 Bureau of Chemistry of the Department of Agriculture, is obtained l>\ the following proportions: a < !yanid of potash (98 percent pure), by weighl ... I ounce avoirdupois. Commercial sulphuric acid, by measure I fluid ounce. Water, by measure :i fluid ounces. This formula differs somewhat from -nine other formulas in use in mill fumigation. 6 Any combination of the three ingredients will produce gas, and hence any one of several formulas which have been recommended and are in use will yield more or Less satisfactory results, hut the greatest economy in materials with a maximum gas production i- secured by following the above proportions. In this formula the acid and water are slightly in excess <'f the exact chemical need-, hut it i- essential that all the eyanid shall he converted ajid that there he sufficient water present to maintain a completely liquid residue. The use of less water, e. i_ r ., two parts, may cause a -olid residue, due to undissolved potassium sulphate, the by-product resulting from the reaction by which hydrocyanic-acid gas i- produced, R 8. Woglum, Hul No. :•>. Bur. Ent., U. S Dept. Alt., p. :):',, Juno 11, 1909. ''The formula 1 1 : 1:3) above quoted may look quite distinct from older ones which have been in Bomewhat general use by millers, rumigators, and others, hut the differ- ence i- v.ry slight and may be explained. The old formula, a.- originally advised by Johnson Fumigation Methods, 1902, p. 163 <. read- substantially that to determine the amount <>f acid and water one-half more acid (liquid measure) than eyanid and ■ ■lie half more water than and are used. Therefore a room _'0 by 30 by 10 feet require- :..! ounces, by weight, ot eyanid; 80 ounce-, liquid measure, sulphuric acid, and 120 ounces, liquid measure, water." as originally advised by Johnson, the sulphuric acid was liquid measure, hut later a more effective formula for fumigating mill-* and similar inclosures came Into use, giving the acid by weight. A formula substantially as follows was substituted with hotter result.-*: mid of potash 98 per cent pure . by weight . . 1 ounce avoirdupois. Commercial sulphuric acid (93 per cent pun by weighl 1} ounces avoirdupois. Water . _'J fluid ounces <>r ounce-, avoirdupois. In |M.int of fact, the formula last quoted substitutes the computation of the acid hv lit for computation bj measure as used in earlier formula- Thus, while the avoirdupois formula remain- nearly the same, owing to the greater atomic weight of the acid, the chemical reaction i- almost identical with the formula I: 1 : :'., which we now ad> i Theoretically the difference in acid between the two formulas i- BO slight that in fumigating mills the results are about equal. In some cases there mighl he a Blight 1 deficiency, resulting in a proportionate d< Bciency in the amount of l*.i- evolved. 795 I ii i 12 10 10 and this solidifying or "freezing" of the residue may prevent com- plete development of the gas, as has been demonstrated. Much recent work by experts and agents of this Bureau has dem- onstrated that for ordinary well-constructed mills or granaries good results may be anticipated by the use of 10 ounces of cyanid of pot- ash and corresponding amounts of the other ingredients to 1,000 cubic feet of air space. This strength, therefore, may be taken as the standard for mill and granary fumigation. If mills could be made practically air-tight, and some are nearly so, undoubtedly a considerably smaller amount of cyanid to each 1,000 cubic feet would give equally good results, but the miller will hardly be willing to risk success by a slight economy in cyanid and acid, in view of the money loss due to "shut downs" incidental to any fumigation. In very loosely constructed or more or less open frame buildings, or where only a short exposure is permissible, it is practically impos- sible to successfully fumigate for most insects affecting stored prod- ucts; but sometimes, by increasing the amount of cyanid to double the quantity normally employed, fair results may be obtained. Good results can not be expected with an exposure of less than 16 or 18 hours, while a period of from 24 to 36 hours is preferable. ESTIMATING AMOUNTS OF CHEMICALS FOR FUMIGATION OF MILLS. The first preliminary to the fumigation of a mill or granary is the making of an accurate estimate of the amount of chemicals required for the different stories of the building. It is desirable to make the computation of space for each floor separately and to prepare a table for the guidance of the operators indicating the number of generators and the amount of chemicals to be distributed on each floor. Inside measurements should be taken, and the height of each stoiy should be carefully measured as well as the floor space. Under ordinary conditions it is best to generate the gas at the standard rate on each floor of the building. The first table which follows illustrates the normal proportions for each floor. These tables are submitted as indications of a convenient method to be followed in making the computations and tabular statement. In view of the fact, however, that the gas is lighter than air and rises, it may be desirable in the case of buildings which have many open- ings from one floor to another, which can not be easily sealed or stopped up, to develop the greatest amount of gas in the basement. a Mr. C. H. Popenoe, working under the instructions of the writer in the vicinity of the District of Columbia, and Mr. D. K. McMillan, fumigating under the writ directions in Kansas, have met with success with lower strengths in fumigating nearly air-tight mills and other structures. [Cir. 112] and n decreasing amount on each of the succeeding floors, maintain ing the total proportion for the building, however, at approximate^ 1 ounces of cyanid to 1 ,000 cubic feet of space, ^n estimate of this kind is illustrated l>\ the second table. Assuming thai the capacity of the upper floor of a given building 16,000 cubic feet, tin- minimum amounts of each reagent and wafer required, according to the same formula, would* be" ' 'van ill of potash 80 pounds avoirdti] Sulphuric acid • •<> pint* Water 180 pints This would necessitat • the use of twentj 3-gallon generators and would naturally require the same number of l>a:_ r - which would con- tain 3 pound- e'ach of the cyanid ^alt. While it i- essential to success that the cubic contents of each floor be accurately computed, it can be readily seen from the foregoing that many of the details as to the strength must be left to the ju< ment of the operator, since we have reports of nonsuccess or of only partial success where greater strengths have been used. As fre- quently happens these reports emanate from distant sources and it has not been possible to give them personal investigation." Whenever a building can not be so t iirht |y closed as in t he case last mentioned and this matter must necessarilj he left to the judg- ment of the operator additional quantities are necessary. This - accomplished by employing, tor each 1,000 cubic feet, one-fourth to one-half more or even twice the quantity of each ingredient. The amounts to be used for other still more loosely constructed buildings can be calculated in the same manner. The following tabular statements are submitted as aids in com- puting the exact proportions for hypothetical buildings of about 1,000 hands (dail) I capacity , The amount- of chemicals to be used for a given building or other inclosure are in direct proportion to the degree of tightness to which it may be closed. Owing to the great variability of buildings and part- thereof as regards tightness, it follow- that no uniform strength can he prescribed. an example, a Wisconsin miller wrote in June, 1909, that, although he had used hydrocyanic-acid gae at the rate oi 2 oun< es of cyanid '" eai h 100 1,000 cubic fe< !••« individual* to have been missed although everything within reach of tin- gae was positively killed. This led t" the conclusion, in which 1 1 1 < >— i millers of experience concur, that l re seldom killed by thi< or other methods "i fumigation now in use, Professor Washburn, how- ever, has succeeded in destroying them, and we fumigated 1 1 mill product in which there \\ ies which later failed '" devi h It should ln> here stated that miller- generally ate very apt to take the outside measurements of a building instead of the inside and do not always calculate with sufficient care the heighl oi each t' fCir. 112] L2 Tables designating dimensions and cubic contents of each floor and amount of chemicals. TEN-OUNCE TABLE. Floor. Dimensions. Cubic feet. Cyanid. Acid. Water. ^entr- ators. Basement 40x60x10 24.000 First lloor * 40 x Ml x Is 13,200 Second lloor 40 x Ml x 1 1 33,600 Third floor 40x60x12 28,800 Fourth lloor 40 x 60 x Is 43,200 Total a : 172 900 108 ins Pounds. Pints. Pints. 15 15 4.", >- 27 si 21 21 63 Is 18 54 27 27 81 324 a Assuming the oosl of cyanid of potash at 25 cents a pound, this would brine the sum for the most expensive chemical to $27. Calculating the sulphuric acid at 3 cents a pound (1 pint= 1.84 pounds) the cost would be $5.96 or $32.96 as the total cost of the chemicals. Table for mills with openings in floors. Floor. Dimensions. f f p t !j' 1 Cyanid. Acid. Water. ators. Basement First floor 40 x 60 x 10 24,000 36 40 x HO x Is 43,200 36 108 36 10* 12 12 Second floor. . . 40 x 60 x 14 33,600 24 24 72 40 x 60 x 12 28,800 12 12 36 40 x 00 x Is 43. 200 s Third floor 4 Fourth floor This table Is intended for use in buildings having large openings, as belt holes, freight elevator shafts, and open stairways in the floors, serving to throw the whole building into one large room. PREPARING THE MILL OR OTHER BUILDING FOR FUMIGATION. After obtaining the chemicals for generating the gas the building should be made as nearly gas-tight as possible, since upon this feature alone depends the amount of chemicals to be used. If the building could be made approximately air-tight, the amount could be mate- rially reduced "with consequent saving of expense. To compass the object desired, every window must be closed as tightly as possible. A good -way is to insert plugs of wood on each side of the top of the lower sash and between the "strip." If this does not make the aperture between the two window sashes tight enough, other substances may be used. Cotton batting of good quality is serviceable for inserting into these openings with a case knife, care being taken that it is packed tightly and not loosely. A cheap grade of batting can be used for stopping other aperture-. Toweling or rags may be substituted, and after being placed under running water can be dried and reused. Macerated newspapers might serve the purpose, but perhaps the best, because the most secure, remedy for general use consists in pasting paper over the aperture, uncalendered paper of the quality of cheap w all paper or any comparatively porous but not pulpy paper being serviceable. Newspapers are apt to be too soft for this purpose. Cracked panes should be replaced, or paper may be pasted over the apertures. [Cir. 112 J 13 Similar treatment should be gives i" the doors and all other natural outlets, including the chimneys, fireplaces, flues, registers, ventilators, cracks in the ceilings and walls, and accidental apertures, such a- rat holes in the floor. All of these should be tight!} closed. li is always advisable that at least two persons be present for a last inspection before the final work of liberating the l,m-. Even aftei all preparations are made an outlet may sometimes be discovered that has escaped not ice. To provide for quick and thorough ventilation after the process is completed two or more opposite windows should be left unlocked and arranged, especially in the upper floors, so that they may be pulled down or up, as the case may be, by means of a muii! cord or rope fron the outside." t i.i. \\t\«, i in: MILL. \- an initial step to the fumigation of a mill or other structure inhabited by the flour moth, it is important to clean it as thoroughly as possible and remove all infested Hour or other mill product and promptly burn it. that as many of the caterpillars, pupa\ and eggs of the insect a-- possible may he destroyed. Most progressive miller- employ a system of cleaning out before fumigating, since before the genera] adoption of fumigation methods in our principal milling cen- ters the only recourse was to close down the mills (which it was found necessary in .some cases i" do a- often as twice a week) and clean out everything by mechanical mean-. It i- feared, however, that too often the sweepings are not properly disposed of by prompt burning. The operation includes the cleaning of all spouts, elevator legs, purifiers, and other part- of the machinery and other equipment, as also the wall-, ceilings, corner- in fact, every portion of the building in which the insect could find lodgment. The reason for cleaning out at tin- time is to afford the gas a better chance to penetrate all parts of the building so as to kill the insects in their various -taire- Every particle of infested flour and w aste material w Inch might harboi the insect or its eggs should he swept down and out until the mill appears t<> he absolutely clean. Then a- soon as possible thereaftei the preliminaries of the actual fumigation should he undertaken. Elevator and hilt brush. For cleaning elevators infested by the Mediterranean flour moth. Johnson long jilt" advised a brush similar to the one illustrated (fig. f '. It is made by taking a piece of 1 I -inch hoard of the same dimensions as the elevator cups, fastening the hrist les to three sides. Side A is fastened to the elevator belt with flat- •The details of arrangement* are considered in » in ulare t i li i - Bureau, which are i »r gratuitous distribution. Hir. UJl 14 headed bolts running through the board, as shown at BB, the bolts being 1-inch or |-inch. The bristles on the sides CC should be |-inch long, but those at 1) should be longer, so that a good brushing to the outer side of the elevator may be secured. Such a brush can be made to lit any size of elevator. As it has been in use for manv veal's and is still advised by the American Miller to correspondents, it is necessarily of value, and something similar should be used in every mill. ( leaning by suction. — For a long time the writer has been endeavor- ing to ascertain if millers have tried the system of vacuum cleaning advertised in our monthly magazines, and has just received word from one of these companies to the effect that it has only recently taken up flour-mill work. The com- pany, however, is satisfied, beyond any question of a doubt, that their system will clean a flour mill more cheaply than can be done by any other process. Con- siderable experiment al work is being done in some of the principal mills ;it Minneapolis, and in one of these a plant was installed some time ago. The diffi- culty in this case is that the steam pressure is not sufficient to work one of the aspirator systems, and this matter is now being inves- tigated with a view to changing the plant to another mill where suit- able conditions can be obtained. Fig. 4. Elevator and belt brush, for cleaning elevators infested by the Mediterranean Hour moth. METHOD OF 'STRINGING A BUILDING FOR FUMIGATION. While the "stringing"' method of fumigating mills and other large buildings is scarcely necessary, there are some persons who may \\ ish information in regard to it. The strings are arranged so as to hang directly over each generator, and are carried through screw eyes in the ceiling or woodwork to doors or stairways leading out of the room to be treated. The screw eyes should be firmly secured, and the best quality of cord of the proper size should be employed. The bags containing the cyanid of potash are suspended directly over the vessels, preferably after the acid is added to the water in the [Cir. mj L5 jui, care being taken thai there is no danger of their dropping into the generator prematurely. A small wire hook attached t" th< of each cord can be used, but if the string is tied firml) around the neck of the sack it causes less trouble and is quite as Becure. The cords ni:i\ be so arranged that the cyanid can all be lowered into the jars bj one motion. The entire process is well shown l»\ the accompany ing illustration I A mure detailed description of the "stringing" process, bj which many l>au r > of cyanid may be lowered into the generators, would require too much -pace for treatment here. The operator, if he chooses this method, may use his own device-. Pulleys and screw Pre. 5 M • aging .1 rooi eyes are practically necessary in the application of the "stringing'' method. The method is much used in greenhouse work and is desirable for small buildings. This process of "stringing" the building would scarcely he found profitable for mills or dwellings, hut in greenhouse work fumigation is frequently done every week or two and often several times a week, and the equipment of screw eyes, pulleys, etc., can remain in place almost indefinitely. as should he placed on the doors of the building that is being fumigated, warning passers-by of the danger, e. g., "Danger!" "Hydrocyanic-acid gas!" "Poison!" The building must, of cot: he vacated and neighbors warned of the nature of the operation. [Clr. u-l 16 Frequently these precautions are not observed, and although no casualties arc on record it is the part of wisdom always to be on the sale side. PROCESS OF FUMIGATION". Tn the process of generating the gas the water is usually measured in a glass beaker indicating ounces, and poured into an earthenware crock or generator. To this is added the acid, measured in the same beaker, which is slowly and gently poured into the water to avoid splashing or boiling. The acid should never be placed in the genera- tors-first, as advised by some writers, since experience shows that this is dangerous, spattering being almost certain to follow. When the acid is poured into the water in the jar an ebullition of vapor sometimes arises. When the cyanid of potash is finally dropped into the combined acid and water mixture an ebullition or bubbling also takes place similar to that which is produced by a red-hot iron dipped into cold water. Next is given off the hydrocyanic-acid gas, the most poi- sonous gas in common use. It is colorless and has an odor which is likened to that of peach kernels." If the fumes are inhaled they are almost certain to prove fatal; hence the necessity of extreme care and the advisability of two intelligent operators in this work. It is even advisable, especially when the first fumigation is undertaken, that one Avho has had experience with this method of fumigation be present to give directions. The odor is decidedly metallic, like that produced by striking two pieces of metal together, or of metal against stone. In preparing cyanid of potash for use it should be broken into lumps about the size of an egg or a little smaller, by pounding it on a stone in the open. The cyanid should never be broken in the hands nor should it be handled without rubber or leather gloves. The smaller fragments, if not too many, are serviceable when equally apportioned as regards large and small particles, and weighed out in 3-pound lots and placed in paper bags or sacks. The bags should be of moderately thin paper, because if as thin as tissue the action of the acid might be so rapid as to constitute an ele- ment of danger. If too thick, action would be delayed or checked, which would militate against the desired results. Before use, the bags should be placed in a can and kept free from moisture, which the cyanid salt is apt to absorb from the air, affording opportunity for leakage through the bag. In some cases, to avoid this leakage, two thin bags, one within the other, might be necessary. Washburn experimented in the use of two sacks with the result that at least 20 seconds elapsed before the gas was evolved. "The writer fails to detect the resemblance. [Cir. 112] 17 As soon ns nil preliminaries have been arranged and the acid has been added to the water in the generators, a bag containing the cyanid should be left at the aide of each generator. After seeing thai the generators are placed in rows so as to afford opportunity for rapid action and the acid has been added to the \\;iicr in each "l" the jars, begin operations in the upper floor of the building mid place the cyanid gentlj in each jar, passing from one jar to another as quicklj as possible and as quickly leaving the room, going downward to the next Hour, where the process is repeated until the last floor or basemenl is reached, where exil is made. The outer doors should l>e locked and a watchman stationed outside until the process is completed. This process ma\ be varied if strings or stoul cords are used for lowering the hairs of cyanid into the jars from the outside, as pre- viously described. A -till (lav should be selected for fumigation. In case "f a high wind the funics of the gas will escape strongly, which will not alone interfere with the success of the fumigation, hut ma\ cause alarm to neighbors should the building not he an isolated one. Better results are claimed for a warm temperature, saj 70 F, or above, than in a temperature as low- as 50 K. or below. Under on most insects become torpid and the effective action of the chemical will he diminished, especially in very low temperature-. The best time that could he chosen, ami which i- generally used where circumstances permit, is during daylight on a Saturday after- noon or very early Sunday morning. This gives a longer exposure than can usually be obtained unless a day preceding a holiday, when all mill hands are on vacation, may be chosen. This permits of a full exposure, as in many cases it removes the necessity of ventilating the building until early the following Monday morning. A single fumigation will in most cases destroy all hut a few indi- vidual insects, especially if conditions are favorable. As a rule, how- ever, it is only a matter of a few days or week-- before the moths may he seen beginning to By about the building or resting on the walls and machinery. To guard againsl reinfestation, therefore, a second treatment must he given, at the end of the third to the fourth week. according to the number of moth- w bich may have issued in the mean- time. If after the expiration of another interval the insects are still present a third fumigation may he accessary. A third treatment i- not usually required, however. Most millers who practice this method of fumigating employ it once a year, some at the intervals above stated, others at intervals of six months. One Michigan miller claims that in hi- case after one thorough fumigation it is unnecessary to repeat the process until two years have elapsed. I fir. 112] 18 The cans or other receptacles containing the cyanid of potash should be plainly labeled "Poison!" and each operator should become thoroughly familiar with the dangers which may attend a failure to carry out directions explicitly. POSSIBLE DANGERS IN USE. As soon as the bag containing the cyanid is dropped into the generator the operator passes quickly to the next generator, and so on. It is not safe to linger under any circumstances or to return in case of any omission. Any deviation from the set rules may mean the loss of life. The residue in the fumigating generator after the operation is completed consists of sulphate of potash, sulphuric acid, and water. Sometimes if the chemicals are not of the proper strength or are not properly combined a certain amount of cyanid of potash remains and hydrocyanic-acid gas is given off. This residue is an element of danger and should not be left in the generators after use, but promptly poured or thrown into a sewer trap or buried. The generator should then be thoroughly cleaned in running water. A question often asked by persons contemplating the employment of the hydrocyanic-acid gas method of treating buildings is as to whether it is dangerous to the contents. It is apt to tarnish, though not permanently, polished brass and nickel when exposed to its action. Where such fittings can be conveniently removed it will save trouble, otherwise they may be treated after fumigation as if tarnished through any other cause. Liquid or moist food materials, such as milk or meats, are apt to absorb the gas and should therefore be removed. It is not positively known that fires are an element of danger, but persons experienced with this process are united in the opinion that to avoid the possibility of risks all fires, gas jets, and the like should be turned off. There is a possibility of explosion when a gas is gen- erated in a tight inclosure, hence the precaution. GENERAL CAUTIONS. After what has been said of the deadly nature of hydrocyanic-acid gas it should be added that there is really no danger if the directions given in this publication are carefully carried out to the letter ami the vapor is not inhaled. Even to taste the salt might have fatal results, and it is dangerous to inhale much gas, as this might cause asphyxiation and death. Undoubtedly thousands of successful funii- a Scores of entomologists and others, including many employees of the Department of Agriculture, have successfully used this gas for fumigating rooms and buildings. It is in general use as a greenhouse fumigant and fur nursery stock and the names of a hundred persons could be mentioned who have had practical experience with it. [Cir. lli'l Ill gations have been made of inclosuree and as jret no fatalities have resulted. Yet it is worth remembering thai operators after making numbers of fumigations, are apt to become careless, a tendency which should be avoided. One form of accidenl sh6uld be mentioned, however. If a matting of newspapers or similar materia] is noi placed under each fumigating jar, or if the water is added to the arid, instead of the reverse as advised in this publication, the acid is apt to run over the generator and injure the floor or splash upon the clothing 01 even the hands of the operator." Such accidents have happened, and t<> pn>\ ide against this contingency a bottle of dilute ammonia should be at hand. If care is observed in labeling the receptacles containing the chemicals, if the operators before using this method become thor- oughly conversant with it, and if signs are placed <>n the doors <>f the buildings, the chances of accidenl will be reduced t" a minimum if not entirely eliminated. After fumigation holdings should never be entered until at least a half hour (an hour or two i- safer) has elapsed after the doors and windows have been opened for ventilation, and under no consideration should an operator return to the place jusi vacated when the operation is under way. 9TJMMAR1 nr OPERATIONS AN D I'IM.< UJTIONS. 1. Use pure chemicals, generators as prescribed, and paper- bags of proper quality. 2. Make every portion of building as nearly gastighl as possible. .">. Make first fumigation in ounces to 1,000 cubic feet of -pace, unless building is unusually loose, in which case more must be used. t. Repeat fumigation at end of three or four weeks if moth- begin flying or other evidence of infestation is shown. 5. Measure every portion of building carefully for calculation ..f the proportions of chemicals. 6. Operators should be intelligent and reliable. Any bookkeeper can readily calculate the cubic contents and proportions of chemicals to use. Careless men should not he employed. 7. Precautions should he made lor prompt ventilation from with- out, after fumigation. During July, 1909, a Michigan miller reported thai while u-ii. ators, It of them boiled over, the c intents Boiling the tl. >■ >r badly. The explanation in this ca.-e was twofold: First, the cyanid was broken into too small lumps, den i u about the sue of coffee berries, and the floors on which the boiling over was » were t ho two upper ones, while no accidenl happened in the basement. This hap- pened during very warm weather, the top floors being hot while the basemenl naturally cool. The miller reported the boiling over as foil - a out of 10 on the third floor, 5 out of 10 en the second, 2 oul of 9 on the iir-t. none in the basement. U'ir. 112] 20 8. Danger signs should be placed in position and a watchman sta- tioned outside 1 until the operation is concluded. 9. Before fumigating clean out the mills thoroughly and provide for the penetration of the gas to every portion by moving bags, boxes, etc. 10. Do not fumigate in a high wind or in a low temperature. Between 0. r )° and 85° F. should produce the best results. 11. Begin operations in the upper floors and pass quickly down- ward, placing the cyanid gently in each jar. 12. Fumigate preferably on a Saturday afternoon, lock the doors after operations are completed, and expose from twenty-four to thirty-six hours if possible. 13. Never reverse the order of procedure. Always pour in the water first, next the acid, and lastly put in the cyanid in bags. 14. The operator should never return to the building after the first fumes begin to issue. 15. Everyone connected with the fumigation should constantly bear in mind the deadly nature of the cyanid and the gas and be con- versant with the process and the necessity of caution before the gas is evolved. ORDER OF PROCEDURE IN FUMIGATION. Briefly, the fumigation of a mill or granary includes the following steps: 1. Measuring the mill and computing the amount of chemicals and number of generators required. '_'. .Securing the chemicals and the generating jars. 3. Preparation of the mill, including cleaning, sealing up as nearly air-tight as possible, and arrangement for ventilation from without after the conclusion of the fumigation, and preparing signs. 4. Distribution of jars and measuring into each the proper amount of water. 5. Breaking up the cyanid and weighing and placing it in 3-pound lots in sacks, temporarily storing it in tightly covered tin cans, preferably a can for each floor. 6. Measuring out the acid and adding to water in jars. 7. Placing a bag of cyanid in each jar, beginning with the top floor. 8. Tightly closing and locking the building and seeing that all warning signs are in place, and, if necessary, stationing a watchman without to guard the building from entrance. 9. Opening the building from without for ventilation. 10. The collection and disposal, in the sewer or in a pit, of the residue, the cleaning of generators, and sweeping out dead insects and other debris before resuming work. [Cir. 112] 21 i i i i . i oi BYDROCYANH \( n> '. \- FUMIGATION < >x SEED MATERIA] A- to the effect of hydrocyanic-acid gas on the germination "f seeds, a series of tests was conducted bj l>r. C. 0. Townsend, qom of this Department, when connected with the Maryland state horti- cultural department, with 1 1 1»> resulting conclusion thai drj grains and other seeds can be treated with hydrocyanic-acid gas for insect pests at the usual strength and time, or even for several days, without ii> jinv \\;i\ poisoning the grain, from which it was deduced that in the ordinary process this method of fumigation can be employed without injuring seeds either for planting or as food. Damp grains and other seeds, however, are more susceptible to the influence of hydrocyanic-acid gas, and some precaution must be observed in such cases i o avoid moist ure. OTHER REM! DJJ 3. While the object of the presenl circular is to furnish information for the fumigation of mills and other buildings by hydrocyanic-acid as ;t remedy for the Sour moth, it would be unwise to omit stat- ing that there are several other good remedies, which, however, are not always possible <>f application. Bisvlphid of carbon. ( me of t hese is bisulphid of carbon, especially for small inclosures. It is claimed by some millers to be of value f<>r ■ first fumigation, following with hydrocyanic-acid gas." When forced into the spouts, machinery, and other portions of the mill, it is a factor in killing the moth and other insects. Cleanliness. The maintenance of scrupulous cleanliness through- out the mill undoubtedly does much toward preventing tin' introduc- tion of the flour moth as well as in restraining its increase after it has once obtained a foothold in the mill. Directions for cleaning have been given on page 13. Prominent millers in some of our large cities, 6. g., in Louisville. Ky. ami in Kansas City, Mo., as elsewhere. have attributed immuni ty from the Hour moth to the facl that they maintain the most rigid system of cleanliness in their mills. Sulphur was used somewhat extensively as a remedy for the flour moth several years before the general employment of hydrocyanic- acid gas, ami it is still valuable ami in constant use by millers in some State-. Lack of space 1 prevents further discussion of this method. Freezing is an inexpensive and valuable remedy where practicable. Where an infested mill can be left open to a temperature of zero or lower, three to ten nights of such exposure continuously or at inter- tails in regard t<> tin- employment of bisulphid of carbon for fumigating build- ings are given in Farmere' Bulletin No. li">. pp. 19 -'i» Other valuable information riling thi^ insecticide i-* also furnished. Copies may !"• obtained gratia on appli- cation t" Members of Congress "r t>> the Secretary of Agriculture, [dr. 112] 22 vals will he found effective in destroying the flour moth in its dif- ferent stages, unless the mill or other huilding happens to be a heated one. The moths are not apt to breed to any extent during the winter, hence there are few eggs to deal with at this time. In north- ern mills which have been much affected by tliis insect, especially in Minnesota and Canada, where the temperature is frequently 20° to 30° F. below zero, this method of destroying the pest has been pur- sued with most excellent results. Speaking generally, it should be practiced wherever the temperature warrants the process. There are, of course, southern mills, e. g., in Kansas and Texas, where this method would not meet with much success. Approved : James Wilson, Secretary of Agriculture. Washington, D. C, January 22, 1910. [Cir. 112] o UNIVERSITY OF FLORIDA r 3 1262 09216 5421