THE RESIDUAL EFFECTS Of INSECTICIDES AGAINST STORED-GRAIN INSECTS Thcsls Io:- IInc Dogma OI M. S. MICHIGAN STATE UNIVERSITY Hari Charan Agarwal 3957 THE RESIDUAL EFFECTS CF INSECTICIDES AGAINST STORED—GRAIN INSECTS by HARI CHARAN AGARWAL AH ABSTRACT Submitted to the College of Science and Arts Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology Year 1957 k‘“ C‘ \ ’//2EE:::7 ;{150./2 ‘: Approved (1L4 ,4Ljf’Z / l NARI CHARAN AGARWAL ABSTRACT Experiments were conducted to evaluate the residual effects of Dowfume-75, Dow Grain Fumigant (SD-2~ Mixture), Dowfume EB-S, Serafume, malathion and DCW-ET-l4 against five common grain pests. The five test insects were: saw-toothed grain beetle, Oryzaephilus surinamensis (L.); confused flour beetle, Tribolium confusum (Duv.); granary weevil, SitOphilus granarius (L.); cadelle, Tenebroides mauritanicus (L.); and larvae of the Indian meal moth, Plodia interounctella (an.). The fumigation of two bushel samples of wheat and corn, according to commercial recommenlations, did not provide any noticeable residual effects against the above insects. In order to duplicate as closely as possible the conditions which exist on the surface of large grain bins, wheat was dipped in the fumigants and the phosphate emul- sions of malathion and DOW-ET-l4. Wheat dipped in emulsions of malathion and DOW—ET-l4 at a concentration of 200 ppm (53 ppm of actual material was deposited on the wheat) provided effective resiiual action against saw-toothed grain beetles, granary weevils and confused flour beetles for seven to ten weeks. DOW-ET—l4 residues were also effective against Indian meal moth larvae. Residues of malathion at ten ppm (1.5 ppm of actual material was deposited on the wheat) were effective against saw-toothed grain beetles and granary weevils for 2 HARI CHARAN AGARWAL ABSTRACT a period of three weeks. DOW—ET-14 residues at the same concentration were not effective against any of the above test insects. Residues on wheat dipped in Serafume gave 70 to 100 percent control of saw-toothed grain beetles and granary weevils for eight and four weeks, respectively. Dowfume EB—S residues were less effective than the Serafume treat- ment, while Dowfume-75 and 80-20 Mixture did not show any significant residual activity. Fumigation at the normal dosages did not reduce the germination of wheat, corn, barley, oat, rye, and kidney bean seeds. ‘J THE RESIUUAL SFFLCTS CV IN CTICID Le] I- A.) C") AJAINiHTEflKIKHI-SRAIR INQLCTE. by HARI CHARAX AGARNAL A THESIS Submitted to the College of Science ani Arts kichigan State University of Agri ulture and Appliei Science in rartial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Entomology 1357 4/30/57 gee? ACKNOWLEDGMENTS Grateful acknowledgment is extended to Professor Ray Hutson, Head of the Entomology Department, for provid- ing the necessary facilities which made this work possible and also for critical reading of the manuscript. The author also wishes to express his sincere thanks to Dr. Gordon Guyer, under whose inspiration, con- stant supervision, and unfailing interest this investiga— tion was undertaken and to whom the results are herewith dedicated. I am also greatly indebted to Dr. Roland Fischer for reading the manuscript and for his valuable criticism and suggestions, and Dr. Oscar Hammer of the Dow Chemical Company, for his interest and constant help during this work. My thanks are also due to Mr. Arthur Wells for his indispensable assistance throughout the course of this study. TABLE OF CONTENTS PAGE I. INTRODUCTION . . . . . . . . . . . . . . . . . I II. LITERATUIE REVIEW . . . . . . . . . . . . . . 3 III. PROCEDURE . . . . . . . . . . . . . . . . . . 14 IV. PRESENTATION OF DATA . . . . . . . . . . . . . 20 V. DISCUSSION OF RESULTS . . . . . . . . . . . . 60 VI. SUMMARY AND CONCLUSIONS . . . . . . . . . . . 67 LITERATURE CITED . . . . . . . . . . . . . . . . . . 7O LIST OF TABLES TABLE PAGE 1. Percent mortality of insects exposed to fumi- gation for 24 hours in grain stored in fiber drums O O O I O O 0 O O O O O O O O O O 21 2. Percent mortality of insects exposed for 48 hours to fumigated grain 48 hours after fumigation in fiber drums . . . . . . . . . . 23 3. Percent.mortality of saw-toothed grain beetles exposed to fumigated grain for seven days at various intervals after fumigation of the grain . . . . . . . . . . . . . . . . . . . . 2S 4. Percent mortality of confusei flour beetles exposed to fumigated grain for seven days at various intervals after fumigation of the grain . . . . . . . . . . . . . . . . . . . . 26 5. Percent mortality of granary weevils exposed to fumigated grain for seven days at vari- ous intervals after fumigation of the grain . . . . . . . . . . . . . . . . . . . . 27 6. Weekly percent mortality of insects placed on fumigated grain two days after fumigation and continuously reared . . . . . . . . . . . 28 7. Weekly percent mortality of insects placed on fumigated grain nine days after fumigation and continuously reared . . . . . . . . . . . 50 8. Weekly percent mortality of insects placed on fumigated grain 16 days after fumigation and continuously reared . . . . . . . . . . . 32 9. Weekly percent mortality of insects placed on - fumigated grain 25 days after fumigation and continuously reared . . . . . . . . . . . 54 10. Weekly percent mortality of cadelles placed on fumigated wheat two days after fumigation and continuously reared . . . . . . . . . . . 37 ll. fieekly percent mortality of caielles placed on fumigated wheat nine days after fumigation and continuously reared . . . . . . . . . . . 58 TABLE 12. 13. I4. 16. 17. 18. 19. 20. 21. 22. 25. Weekly percent mortality of cadelles placed.on fumigated wheat 16 days after fumigation and continuously reared . . . . . . . . . . . . Percent emergence of Indian weal moth adults from cultures of larvae exposed to fumigated wheat for five weeks . . . . . . . . . . . Percent mortality of saw-toothed grain beetles exposed for seven days to wheat dipped in insecticides at various intervals after treatment of the grain . . . . . . . . . . Percent mortality of granary weevils exposed for seven days to wheat dipped in insecti- cides at various intervals after treatment of the grain . . . . . . . . . . . . . . . Iercent mortality of confused flour beetles exposed for seven days to wheat dipped in insecticides at various intervals after treatment of the grain . . . . . . . . . . Weekly percent mortality of insects placed on wheat iipped in insecticides seven days after treatment and continuously reared . . Weekly percent mortality of insects placed on wheat dipped in insecticides 14 days after treatment and continuously reared . . . . . Weekly percent mortality of insects placed on wheat dipped in insecticides 21 days after treatment and continuously reared . . . . . Weekly percent mortality of insects placed on wheat dipped in insecticides 28 days after treatment and continuously reared . . . . . Weekly percent mortality of insects placed on wheat dipped in insecticides 35 days after treatment anl continuously reared . . . . . Weekly percent mortality of insects placed on wheat dipped in insecticides 42 days after treatment and continuously reared . . . . . Neekly percent mtrtality of insects placed on wheat dipped in insecticides 4) days after treatment and continuously reared . . . . . 4D 42 II 5 44 If. 4/; 46 47 4s 49 SO vi TABLE PAGE 24. Weekly percent mortality of insects placed on wheat dipped in insecticides 56 days after treatment and continuously reared . . . . . . 51 25. Weekly percent mortality of insects placed on wheat dipped in insecticides 65 days after treatment and continuously reared . . . . . . 52 26. Percent emergence of Indian meal moth adults from cultures of larvae exposed for five weeks to wheat dipped in insecticides . . . . 56 27. Percent emergence of Indian meal moth adults after three week exposure of larvae to wheat dipped in insecticides . . . . . . . . . . . 57 28. Percent germination of seeds before and after fumigation . . . . . . . . . . . . . . . . . 59 INTRODUCTION Man has been fighting insects since time immemorial in one way or another. Insects are so numerous and diver- sified that they are present in almost every type of hab- itat. Stored grain and stored products are no exception to this. About ten percent of the world's production of cereals, pulses and oil seeds are destroyed annually by various pests, mainly insects. In the United States the losses from insects to cereal grains and their products have been variously estimated to be from 200 million to 600 million dollars annually. With the increase in the amount of stored products we are faced with a serious problem of saving our grain from insects. Many studies have been conducted in the past half century regarding the protection of stored products. At the present time fumigation is considered one of the most successful means of combating insect infestations. Methyl bromide is one of the most recent fumigants to be used successfully for grain fumigation. Recent problems asso- ciated with the residues resulting from the application of methyl bromide and other fumigants have increased the in- terest in some of the older formulations. The increase in surface infestations of the Indian meal moth, Plodia in- terpunctella (an.), in many grain storages has also fo- cused attention to the residual activity of various fumi- gents. The objective of this study was the evaluation of the residual effectiveness of various formulations of fu— migants against the following five stored grain pests: confused flour beetle, Tribolium confusum (Duv.); saw- toothed grain beetle, Oryzaephilus surinamensis (L.); granary weevil, SitOphilus granarius (L.); Indian meal moth, Plodia interpunctella (an.), and cadelle, 2323; broides mauritanicus (L.). LITERATURE REVIEW One of the oldest fumigants known was the fumes of burning sulfur. It had been used for the fumigation of houses for thousands of years and was a common practice as early as the 12th century B. C. Hydrocyanic acid (prussic acid) was known by Egyptians as a poison derived from ex- tracts of the peach and other plants. The Romans acquired this knowledge and used the poison for suicidal purposes (Blyth, 1895). Its use as an insect fumigant to kill mu- seum pests in insect collections was recorded by Bell (1877). Coquillett (1888) used hydrocyanic acid for con— trol of the cottony cushion scale, Icerya purchasi Mask. In 1922 a mixture of liquid hydrocyanic acid and chloro- picrin absorbed on diatomaceous earth was developed in Germany for generalfumigathmawork. It was used by Metder (1926) to a limited extent for local fumigation work in flour mills. The great development of fumigants for in- secticidal purposes has taken place during the past fifty years. The use of carbon disulfide as an insect fumigant was discovered by Garreau (1854) for control of the gran- ary weevil. His results indicated that carbon disulfide was the most satisfactory material for control of this pest. Since about 1880 the use of carbon disulfide has steadily increased, chiefly as a soil insecticide for the control of rats, gOphers and ants. Chittenden (1897) rec— ommended its use in general fumigations of stored products in warehouses. Hinds (1909) and Hinds and Turner (1910) extended the use of carbon disulfide to the control of in- sects in stored corn. The mixture of carbon disulfide vapors and air is a highly flammable mixture and for this reason it is consid- ered unsafe for use as a fumigant. In order to reduce the fire hazard associated with the use of carbon disulfide many mixtures with non-flammable-chemicals such as carbon tetrachloride have been prOposed (Cotton, 1956b). Mix- tures containing about 15 percent carbon tetrachloride to- gether with other ingredients are relatively stable and can be used safely. ChlorOpicrin was important in chemical warfare dur- ing World War I as one of the tear gases known commonly as "vomiting gas." According to Roark (1934) it was first prepared by Stenhous in 1848. According to Cotton (1956b) the insecticidal use of chloropicrin was first prOposed in 1907 by Fabricwerke of Austria. Moore (1918) discovered its value as an efficient insect fumigant. Piutti and Bernadini (1917) in Italy, and Bertrand (1919) in France published papers on the effect of chlorOpicrin on stored product insects. Chapman and Johnson (1925) reviewed the history of chlorOpicrin research and determined some of the limitations for its use in cereal fumigation. It is extremely toxic to insects and non-flammable, but is dis- agreeable to handle because of its lachrymatory and nause- ating effects. Its vapors cling to fumigated commodities and seriously decrease the germination of seeds when mois- ture content is high or if used in heavy dosages for long exposures (Cotton, 1956b). Morse (1910) employed carbon tetrachloride for the first time as a fumigant for control of insect pests in stored grain and grain products. Chittenden and Pepenoe (1911) tested it as a substitute for carbon disulfide for fumigating stored grain and published an account of its effectiveness. Doane (1919) reported the successful use of carbon tetrachloride for controlling Sitophilus 23133 (L.) and Sitophilus granarius (L.) at the rate of two gal- lons per 1000 bushels of wheat. It was recognized shortly after the discovery of its use as a fumigant that carbon tetrachloride is not as effective as carbon disulfide and at the present time it is more frequently used in combina— tion with other chemicals more toxic to insects. These combinations reduce the fire hazard and aid in the distri- bution of the fumigant by increasing the volume of the mixture. . Neifert gt 5; (1925) found that ethylene dibromide mixed with carbon tetrachloride was a promising fumigant for stored grain. Ethylene dichloride mixed with carbon tetrachloride was employed in the fumigation of stored products by Cotton and Roark in 1927. Later, Cotton and Wagner (1941) recommended a mixture of ethylene dichloride and carbon tetrachloride (75:25) for the fumigation of wheat. -Farrar and Flint (1942) extended its use to corn. Cotton and Roark (1928), in an effort to find an acceptable substitute for carbon disulfide as a grain fumigant, dis- covered the insecticidal prOperties of ethylene oxide. Cotton and Young (1929) reported that by mixing carbon di- oxide with ethylene oxide the insecticidal action of ethylene oxide was increased while the fire hazard was re- duced. Methyl bromide is one of the most recent additions to the list of the fumigants. Le Goupil (1952) used it to eliminate the fire hazard of ethylene oxide and he discov- ered it to be even more effective than the compound with which it was mixed. Vayssiére (1954), de Francolini (1956) and Lepigre (1956) in France reported on the insec- ticidal uses of methyl bromide and noted its effectiveness against grain-infesting insects. Hicks and Dabney (1897) reported that field corn is one of the seeds most susceptible to injury by gas treat- ment. In their experiments, the germination of corn treated for 48 hours with a standard atmosphere of gas was reduced 40 percent. A 24-hour treatment resulted in no injury. Hinds in 1909 conducted tests to find the effect of carbon disulfide on the germination of seed corn. He used carbon disulfide at the rate of 75 pounds per 1000 cubic feet. The seeds, soaked with water before exposure of 40 and 72 hours, were all killed. Others which were soaked in water and then aired showed an injury of about 27 percent. He concluded that the proportion of water in the seeds at the time of treatment has much to do with the possibility of gas injury. Moore (1918) reported that small doses of chloro- picrin, such as one-half pound per 1000 cubic feet of space, did not injure the germination of certain grain seeds. Higher concentrations did reduce the germination when it was attempted before the grain was aired thorough- ly. He further noted that pure chlorOpicrin did not change the color or baking prOperties of flour. Willard (1925) working with carbon disulfide found that, in practice, no aeration of storages was necessary after fumigation with carbon disulfide, unless they were air tight. Bins and similar storages for seeds seldom are air tight and the carbon disulfide would diffuse out of the bin. It required large concentrations of carbon di- sulfide for an extended period of time to have any marked effect on the germination of seeds used in the experiment. 8 The injury slowly became greater as the time and the rate increased but was not directly preportional to either va- riable. The first effect of the treatment was to delay germination one or more days later than the check. Wil- lard also observed that when liquid carbon disulfide was poured directly on most seeds during fumigation it did not cause serious injury. Roark and Cotton (1928) during their tests of vari- ous aliphatic chlorides as fumigants for stored grains in- dicated that these compounds when used at normal dosages do not injure the germinating qualities of the grain. Shepard and Buzicky (1959) found that ethylene di- chloride, unlike many other fumigants, produced a delayed mortality for the first ten days after fumigation. Richardson and Casangec (1942) working along the same line found that this delayed effect continued beyond ten days. In some of their tests 40 to 63 percent of the confused flour beetles were killed between the tenth and twentieth days. There was only slight increase in mortality between the twentieth and fortieth days. The mixture of ethylene dichloride with carbon tetrachloride was found to have a similar latent effect, while carbon tetrachloride alone did not produce this delayed mortality. Cotton (1944) working with methyl bromide and chloropicrin reported that these materials may cause se- vere losses in germination of wheat with low moisture con- 9 tent. Smith and Staten (1942) pointed out that damage to the germ of wheat by fumigants may impair the baking value. Cotton further noted that with many fumigants germination injury increased if grain moisture is above 12 percent, if the concentration is excessive, or the exposure period prolonged. A three to one mixture of ethylene dichloride and carbon tetrachloride did not retard germination of grain, regardless of the above factors. Richardson and Walkden (1945) obtained 100 percent mortality of rust red flour beetle, saw-toothed grain beetle and rice weevil with the use of 20 percent p-— methylallyl chloride at the rate of two gallons per 1000 bushels of shelled corn stored in steel bins. The germi- nation was not reduced in corn and wheat treated as above and containing 9.1 percent moisture. Injury to germina- tion increased with the increase in dosage or moisture content of the grain. They also observed no reduction in the germination of corn and wheat fumigated with the ethylene dichloride-carbon tetrachloride mixture (25:75). Fisher (1945) found that when methyl bromide was applied at the rate of two pounds per 1000 cubic feet for a period of 24 hours, there was a retention of 2.6 ppm (expressed as bromide) in raisins, 1.6 ppm in dried peaches, 2.8 ppm in dried apricots and a trace in prunes. Rolled oats had a residue of 150 ppm and raw cashew nut- meats 148 ppm, 48 hours after fumigation. Oil—bearing lO foods tend to absorb more of the oil soluble methyl bro— mide. Farrar and Wright in 1946 found that the use of DDT at the normal rates had no deleterious effect on the ger- mination of wheat, barley and oats. Richardson (1946), while comparing the efficiency of the carbon tetrachloride-ethylene dichloride mixture on shelled corn, found that the effective dosages of carbon tetrachloride (two gallons per 1000 bushels for 24 hours) did not injure the germination of seed corn even when the fumigant was poured directly on the corn. Grayson (1948), while testing the effect of chloro— picrin On the germination of shelled peanuts at rates up to ten pounds and for exposures of 24 hours, found that at a moisture content below ten percent very little reduction in germination occurred. At moisture contents greater than 14 percent slight reduction in germination resulted from a two pound rate and the germination reduced consid- erably at higher rates. Glass and Crosier (1949) tested the effects of acrylonitrile-carbon tetrachloride mixture (50:50) on ger- mination of bean, beet, cabbage, carrot, corn, cucumber, lettuce, lima bean, oat. onion, pea, pumpkin, radish, squash, tomato and wheat seeds. The fumigant was used at dosages varying from one to 25 pounds per 1000 cubic feet. No evidence was found of immediate or delayed deleterious effect on germination of any of the seeds. ll Smallman (1949), in an effort to find a fumigant with long residual action for use in milling machinery, tested compounds with low vapor pressure. He found that fumigants with low vapor pressure and high toxicity have a longer residual life. Ethylene dibromide with a vapor pressure as low as 15.5 mm. of mercury at 25°C. gave 100 percent mortality for 20 days. Gerhardt, Lindgren and Sinclair (1951) pointed out that when whole walnuts stored in sealed, double-walled cellophane bags were vacuum-fumigated with two pounds of methyl bromide per 1000 cubic feet, the methyl bromide persisted over a period of one hour to 21 days within the bags and the nuts absorbed 0.41 to 4.84 mg. bromide per 100 gms. Walkden and Schwitzgebel (1951) noted that carbon tetrachloride, when applied to 1000 bushels of wheat in a steel bin at the rate of two gallons per 1000 bushels, was retained in lethal concentrations from two to three weeks. .An increased rate of application extended the time of re— tention of the fumigant in lethal concentrations. The mix- ture of carbon disulfide-carbon tetrachloride (1:4), when applied to 1000 bushels of wheat at the rate of two gallons per 1000 bushels, was retained in lethal concentrations for two to four weeks. Increased rate also prolonged the time of its retention on the wheat. A mixture of ethylene dichloride and carbon tetrachloride (5:1) was retained in 12 lethal concentrations for four to five weeks when three gallons of this formulation was applied to 1000 bushels of wheat. It was retained for 24 to 32 weeks when 5000 bush- els of wheat were treated at the same rate. Lindgren, Krohne and Vincent (1954) observed that rice weevils, granary weevils and lesser grain borers, when exposed to malathion-treated grain, were killed at dosages as low as two ppm. After storage for three months the kill of these insects was relatively high, especially when the malathion was applied to the grain as a dust. Concentrations of eight and 16 ppm were still effective six to seven months after application. The insects ovi- posited normally prior to their death in the treated wheat. In cases where 100 percent mortality occurred there was no evidence of breeding four months after treat— ment. The same workers also reported that the tests under progress indicate that the residual effectiveness of the malathion treatment may be affected by the moisture con- tent of the grain. Berck (1956) recently pointed out that fumigant containing ethylene dibromide and carbon tetrachloride showed greater insecticidal effectiveness than a fumigant containing ethylene dibromide and methyl bromide. He ex- plained this phenomenon by the improved downward distribu- tion and persistence of ethylene dibromide when carbon tetrachloride is present. When ethylene dibromide and 15 methyl bromide mixture was applied to wheat, bromide resi- dues were found on the fumigated wheat. PROCEDURE Field run samples of corn and wheat were place in fiber drums. Ten drums contained two bushel samples of .corn and ten additional drums were used for two bushels of wheat. The fiber drums had a diameter of 20 inches and a height of 51 inches. The drums were filled to a depth of 12 and 14 inches with two bushels of corn and wheat, re- spectively. The exposed surface area of the grain was 514.2 square inches. Ten drums, five of corn and five of wheat, were kept in a storage room in the Natural Science building. The remaining ten drums were placed in a screened insectary where they were exposed to outside tem- peratures but protected from rain. During storage, drums in the Natural Science building were covered with a metal cover and those at the insectary remained open. The con- ditions of storage in the drums in the Natural Science building were very similar to those in tightly closed grain storage. The grain at the insectary was eXposed to conditions representative of those in Open farm storage. Small cages, 2.5 inches long and 0.75 inch in di- ameter, were filled with 150 insects. Each cage contained 59 saw-toothed grain beetles, Oryzaephilus surinamensis (L-); 50 confused flour beetles, Tribolium confusum (Duv.) 15 and 50 granary weevils, Sitgphilus granarius (L.). Larger screen cages, 4 inches long and 0.75 inch in diameter, were filled with wheat flour containing eggs, larvae and pupae oi the confused flour beetle.) The cages were then fastened together in pairs with rubber bands. Each pair consisted of one small ani one large cage. In each drum two such pairs of cages were inserted in the grain in an upright position, one pair at the bottom ani the other pair near the surface. A small cheese-cloth sack contain- ing more than 100 seeds each of wheat, corn, rye, barley, oats and kidney beans was placed at the bottom of each drum. The drums were fumigated on July 9, 1956. The fumi- gant was evenly distributed over the surface of the grain by means of a small Sprinkler consisting of a rubber ball of 50 cubic centimeter capacity,attached to a narrow glass tube which tapered to a fine Opening. The fumigants used were all commercially prepared materials. They were: Dowfume-75, consisting of 70.2 percent ethylene dichloride and 29.8 percent carbon tetrachloride; Dow Grain Fumigant (80-20 Mixture), consisting of 95.5 percent carbon tetra- chloride and 16.5 percent carbon bisulfide; Dowfume EB-S, consisting of 7.2 percent ethylene dibromide, 29.2 percent ethylene dichloride and 65.6 percent carbon tetrachloride; and Serafume, consisting of 5.5 percent ethylene dibromide, 13.3 percent carbon disulfide, 10.0 percent ethylene di- l6 chloride and 76.5 percent carbon tetrachloride. Slightly more than the recommended dosages were used, because of the small amount of the grain fumigated. Four drums, two at the Natural Science building and two at the insectary, were fumigated with each material. . One drum of corn anl one of wheat were treated at each lo- cation. The remaining drums were left untreated as checks. ‘All drums were covered immediately after fumigation and opened after 24 hours for aeration of the grain, and all of the cages were removed. Thirty-six hours after fu- migation the drums stored at the Natural Science building were covered. The small cages were transferred to a con- stant temperature and humidity rearing room maintained at 80° F. and 50 percent humidity. Each large cage contain- ing infested wheat flour was emptied into a one-half pint, wide mouth glass jar and covered with white muslin. These samples were placed in the rearing room for future obser- 'vations. The mortality of the insects in the small cages ‘was determined after 72 hours. Twenty-four hours after removing the first series of cages a second series was jplaced in the grain. These cages were taken out after 48 hours and the same process as above was followed. Forty-eight hours after fumigation approximately one-half pint of grain was taken from both the surface and the bottom of the grain in each drum. Two samples of 50 gms. each were taken from the surface, and one from the 17 bottom of the grain in each drum, and placed in one-half pint,wide mouth glass jars and covered with muslin, Ten Indian meal moth larvae, Plodia interpunctella (an.), about one-half inch long, were placed in one of the sur- face samples, and in the second as well as the bottom sample 50 adults each of confused flour beetle, saw- toothed grain beetle and granary weevil. Ten adult ca~ delle, Tenebroides mauritanicus (L.), were placed in 5D- gram samples of the fumigated and unfumigated wheat stored at the Natural Science building. The jars containing these samples were placed in the rearing room. After one week the number of dead insects and the number of Indian meal moth adults that had emerged was recorded. The num— ber of adult confused flour beetles emerging in the flour was noted. The sampling procedure as outlined above was continued for four weeks. Mortality counts and observa- tions were continued until the second generation adults appeared. A second series of experiments was established by actually dipping samples of wheat into the fumigant. Ap- proximately five pounds of wheat was dipped in a fumigant for one minute, after which it was spread on a sheet of paper to dry. The materials used were Dowfume-75, Dow Grain Fumigant (80-20 Mixture), Dowfume EB-5, Serafume, DOW+ET-l4 (four pounds DOW-ET-l4 per gallon), and Malathion (premium grade, five pounds per gallon). Malathion and 18 DOW-ET-l4 were use-d at the concentrations of ten and 2‘30 ppm. Since about 256 cubic centimeters of the emulsion we re retained by the grain, calculation shows there was approximately 1.5 ppm (10 ppm) and 50 ppm (200 ppm) of ac- tual malathion and of DOW—ET-l4deposited on the wheat. The dipped grain was allowed to dry for 12 hours and ' then divided into two lots of 2.5 pounds each. Each lot was placed in a wide mouth gallon .jar. This resulted in 18 jars, eight containing grain dipped in fumigants, eight with grain dipped in DOW-ET-l4 and malathion emulsions, and two containing untreated wheat. Nine jars were stored in the Natural Science building and the other nine were kept at the insectary as in the previous case. The .jars in the Natural Science building were covered and those at the insectary remained Open. Two samples of 50 grams each were removed from each jar weekly. Ten Indian meal moth larvae were introduced in one sample. In the other sample 50 adults each of saw- toothed grain beetle, confused flour beetle and granary Weevil were introduced. These cultures were maintained in the rearing room at the temperature and humidity as above. The number of dead insects and the number of the Indian meal moth that had emerged were recorded each week. This SaKipling procedure was continued for eight weeks. Seed germination tests were conducted before and 8‘fter the fumigation. Before fumigation 2’30 seeds each of 19‘ wtueat, corn, rye, barley, cat, and kidney bean were test- ed. by the upright paper towel method. The number of seeds geirminated after six days was recorded. The sacks contain- ing; the seeds for germination studies were removed from ‘Crue drums five weeks after fumigation. Germination studies of‘ these seeds were conducted as above. PRESENTATION OF DATA The exposure of confused flour beetle, saw-toothed pyrain beetle and granary weevil adults to the normal dos- efges of Dowfume-75, Q0-20 Mixture, Dowfume EB-5 and Sera- ffidme normal fumigation procedure for twenty-four hours in “dieat and corn resulted in the mortality shown in Table l. Tnie mortalitv of the three species of insects approached 1(30 percent. In the case of Dowfume—75 all of the insects wnare killed both at the bottom and near the surface of the snrain except in one drum of wheat located at the insectary. Iri this drum 54 percent of the granary weevils were killed iri the cage near the surface of the wheat. In the same “fldeat 94 percent of the confused flour beetles and ten Emercent of the granary weevils were killed in the cage at tlle bottom of the drum. With the exception of one drum of wheat fumigated unith Serafume, 103 percent mortality of the insects lo- ciated both at the bottom anl near the surface of the grain “Was obtained by fumigation with ED-2O Mixture, Dowfume EB-—5 and Serafume. In one drum of wheat treated with SGirafume anl located at the insectary, 39 percent of the e C?‘ r L gtwsnary weevils were killed in the bottom cage. In Ch“mks the mortalit‘ was low, the highest being in the TABLE 1 PERCENT MO?TALITY CF IN‘EC‘S FOR 24 HOURS IN GRAIN STORED IN FIBER DRUMS BKIOSBD t.“ f‘, L V 0) ’4 FUMIGATION 1! Percent of dead insects Position . ,. . Type of of insect Oryzae- Tri- Material eraln storage cage philus bolium SitOphilus in grain surina- con- granarius mensis fusum Dowfume Wheat Closed Surface 103 100 100 EB-5 " " Bottom 100 100 100 Corn " Surface 100 100 100 " " Bottom 100 100 100 Wheat Open Surface 100 100 100 " " Bottom 100 103 100 Corn " Surface 100 100 100 " " Bottom 100 100 100 Serafume Wheat Closed Surface 10) 103 103 " " Bottom 100 100 100 Corn " Surface 133 130 130 " " Bottom 100 130 100 Wheat Open Surface 100 103 100 " " Bottom 100 100 98 Corn " Surface 100 100 100 " " Bottom 100 100 100 50:20 Wheat Closed Surface 100 100 100 Mixture " " Bottom 100 100 100 Corn " Surface 100 100 100 " " Bottom 100 100 100 Wheat Open Surface 100 100 100 " " Bottom 100 100 100 Corn " Surface 100 100 100 _n " " Bottom 100 100 100 Dggfume' Wheat Closed Surface 100 100 100 " " Bottom 100 100 100 Corn " Surface 100 100 100 " " Bottom 100 100 98 Wheat Open Surface 100 100 54 " " Bottom 94 100 10 Corn " Surface 100 100 100 __l " " Bottom 100 100 100 Check Wheat Closed Surface 0 0 4 " " Bottom 6 0 20 Corn " Surface 2 2 8 " " Bottom 6 2 2 Wheat Open Surface 0 0 l6 " " Bottom 6 0 6 Corn " Surface 10 0 18 " " Bottom_ 8 2 20 {{ 22 case of the granary weevils, where 20 percent of the in- sects were dead. mortality was zero to ten percent in the case of the saw-toothed grain beetles, zero to two percent with the confused flour beetles anl two to 20 percent in the case of granary weevils. The second set of insects was exposed to the fumi- gated wheat and corn, 4? hours after fumigation, for a period of 49 hours to obtain data on residues from normal fumigation. The data in Table 2 indicates that the high- est kill was obtained with Dowfume 3B—5. In the covered drums the mortality of saw-toothed grain beetles (Table 2) placed on fumigated grain 49 hours after aeration varied from 60 to 94 percent, granary weevils from 48 to 76 per— cent and confused flour beetles 18 to 78 percent. The mortality was less in the samples stored in the Open drums. In these drums the mortality of saw-toothed grain beetles varied from 12 to 50 percent, granary weevils 54 to 46 percent and the confused flour beetles zero to two percent. The mortality resulting from the various fumi- gants decreased in effectiveness in the following order: Dowfume EB—5, Serafume, Dowfume-75 and 80—20 Mixture. A mortality of zero to 12 percent for the saw-toothed grain beetles, six to 58 percent of the granary weevils and zero to four percent in case of the confused flour beetles was noted in the checks. In all cases higher mortality was observed in closed drums than in Open drums. It was appar- TABLE 2 25 PERCENT MORTALITY OF INSECTS EXPOSED FOR 48 HOURS TO FUMIGATED GRAIN 48 HOURS AFTER FUMIGATION IN FIBER DRUMS Percent of dead insects Position - n . Type of of insect Oryzae— Tri- Material grain storage cage philus bolium Sitophilus in grain surina- con- granarius mensis fusum Dowfume Wheat Closed V Surface 82 4O 76 EB-5 " " Bottom 60 18 54 Corn " Surface 66 5O 6O " " Bottom 94 78 48 Wheat Open Surface 12 2 42 " " Bottom 26 2 46 Corn " Surface 16 0 42 :3" " Bottom 50 0 54 Serafume Wheat Closed Surface 0 6 42 " " Bottom 14 0 60 Corn " Surface 62 16 80 " " Bottom 64 24 76 Wheat Open Surface 8 2 54 " " Bottom 10 4 42 Corn " Surface 2 2 50 __ " " Bottom 6 2 42 80-20 Wheat Closed Surface 6 0 28 Mixture " " Bottom 6 2 54 Corn " Surface 4 O 48 " " Bottom 4 4 58 Wheat Open Surface 2 0 44 " " Bottom 14 0 58 Corn " Surface 0 O 26 __. _" " Bottom 2 4 14 Dowfume- Whéat Closed Surface 8 86 56 " " Bottom 26 96 5O Corn " Surface 2 18 50 " " Bottom 8 70 26 Wheat Open Surface 4 6 56 " " Bottom 2 6 26 Corn " Surface 0 4 52 _.____g " " Bottom 0 0 16 Check Nheat Closed Surface 6 O 28 " " Bottom 6 0 26 Corn " Surface 12 O 58 " " Bottom 4 0 6 Wheat Open Surface 0 0 l4 " " Bottom 4 O 52 Corn " Surface 0 0 54 " " Bottom 2 4 2O A 24- ent that the fumigants were retained for a longer time in the closed storage conditions. There was no emergence of adult confused flour beetles from the rearing of its eggs, larvae and pupae in flour exposed to fumigants in the first and second sets of cages. The checks also showed the same results. The residual effect of the fumigants on the mortal- ity of adult saw-toothed grain beetles, confused flour beetles, confused flour beetles and granary weevils ex- posed to the samples of fumigated wheat and corn are re- corded in Tables 5 to 9. The first three tables present the results of one week's exposure of the above three spe- cies of insects. Little residual effect was observed in the case of saw-toothed grain beetles during the one-week eXposure. The data in Table 5 indicate that the mortality in the checks and treatments were comparable. This same trend was present in the case of confused flour beetles (Table 4) and granary weevils (Table 5). The data in Tables 6 to 9 indicate that there was also no residual ef- fect to these three insects when they were continuously reared on the fumigated wheat and corn. When adult cadelles were maintained on samples of fumigated wheat, there was some indication of residual ac- tion. The fumigants ranked in the following order of de- CPeasing effectiveness: Dowfume-75, 80-20 Mixture, Dow- fixme EB-5 and Serafume. 1n the samples taken two days l\) \p TABLE 5 PERCENT MORTALITY CF SAW-TOOTHED GRAIN BEETLES EXIOSED TO FUMIGATED GRAIN FOR SEVEN DAYS AT VARIOUS INTERVALS AFTER FUKIGATION OF THE GRAIN I I :— L Percent of dead insects . . Type of Sample . . Material Grain storage position Days after fumigation 9 16 25 50 Dowfume Wheat Closed Surface 2 10 O 2 EB-S " " 'Bottom 0 4 2 2 " Open Surface 4 2 O 2 " " Bottom 4 4O 0 4 Corn Closed Surface 0 O 4 4 " " Bottom 0 2 O 2 " Open Surface O 2 4 4 ; " " Bottom 0 8 6 +2 Serafume Wheat CIosed Surface O 2 2 8 " " Bottom 3 2 O 4 " Open Surface 0 6 O 2 " " Bottom 0 76 2 8 Corn Closed Surface 0 6 O 4 " " Bottom 0 l6 l2 2 " Open Surface 0 S 4 4 " " Bottom 0 4 6 6 30-25 Wheat Closed Surface O 2 4 2 Mixture " " Bottom 0 O 2 2 " Open Surface 2 l2 4 O " " Bottom 2 l2 4 0 Corn Closed Surface 2 2 4 2 " " Bottom 0 8 O O " Open Surface 3 2 6 2 _: " Bottom 2 fl 2 O Bowfume- Wheat Closed Surface O 10 12 2 75 " " Bottom 2 O O 6 " Open Surface 4 2 2 O " " Bottom 0 8 4 2 Corn Closed Surface 0 2_ 6 O " " Bottom 0 O O O " Open Surface 0 O O 2 __f " " Bottom O 10 2 0 Check Wheat Closed Surface 2 2 O 2 " " Bottom 0 O 4 2 " Open Surface 2 6 O O " " Bottom 0 2 O 0 Corn Closed Surface 2 4 O O " " Bottom 2 4 4 2 " Open Surface 2 4 O O " " Bottom 0 4 6 O I! PERCENT MORTALITY OF FUMIGATED GRAIN FOR TABLE 4 CONFUSED FLOUR BEETLES EXPOSED TO SE EN DAYS AT VARIOUS INTERVALS AFTER FUMIGATION OF THE GRAIN Percent of dead insects Material Grain ggggaég pggggIgn Days after fumigation 9 16 23 30 Dowfume Wheat Closed Surface 10 30 4 O EB-S " " Bottom 30 6 O O " Open Surface 0 2 O O " " Bottom 2 4 6 0 Corn Closed Surface 24 2 4 O " " Bottom 20 O O O " Open Surface 2 8 O O " " Bottom O 4 O O Serafume Wheat CIosed Surface 40 18 O O " " Bottom 26 12 4 2 " Open Surface 2 4 O O " " Bottom 0 18 O 2 Corn Closed Surface 14 2 O O " " Bottom 26 18 O O " Open Surface 0 2 O O " " Bottom 0 2 O 2 30-20 Wheat Closed Surface 0 16— 2 O Mixture " " Bottom 22 16 4 O " Open Surface 4 8 O O " " Bottom 0 24 4 0 Corn Closed Surface 22 14 O O " " Bottom BO 12 2 O " Open Surface 0 2 O O I" " Bottom 0 8 O O Dgwfume Wheat Closed Surface 4 34 O 2 " " Bottom 56 28 2 O " Open Surface 2 6 2 O " " Bottom 0 6 O 2 Corn Closed Surface 22 18 2 O " " Bottom 18 6 O O " Open Surface 0 2 O O ___ " " Bottom 10 8 O 0 Check Wheat *CIosed Surface 4O 14 '2 O " " Bottom 54 8 O O " Open Surface 0 4 O O " " Bottom O 12 2 0 Corn Closed Surface 26 O O O " " Bottom 38 8 6 O " Open Surface O 10 O O " " Bottom 0 12 O O TABLE 5 |'\) \J PERCENT MORTALITY OF GRANARY WEEVILS EXPOSED TO FUMIGATED GRAIN FOR SEVEN DAYS AT VARIOUS INTERVALS 4 r AFTER FUMIGATION OF THE GRAIN Percent of dead insects Material Grain :{ggagg pgzggIgn Days after fumigation 9 16 23 30 Dowfume Wheat Closed Surface 10 0 0 4 EB-S " " Bottom 6 2 O 8 " Open Surface 14 2 O 4 " " Bottom 10 12 0 2 Corn Closed Surface 8 2 0 0 " " Bottom 6 0 4 0 " Open Surface 0 0 O 8 " " Bottom 2 2 O 2 Serafume Wheat Closed Surface S 0 O 2 " " Bottom 8 2 2 O " Open Surface 16 2 O 2 " " Bottom 8 0 O 4 Corn Closed Surface 4 O 0 6 " " Bottom 0 0 2 0 " Open Surface 2 O O 2 I " " Bottom 6 4 0 2 80-20 Wheat Closed Surface 2 6 0 O Mixture " " Bottom 2 2 0 0 " Open Surface 4 4 2 O - " " Bottom 14 0 O 0 Corn Closed Surface 2 0 2 O " ‘ " Bottom 2 0 0 O " Open Surface 6 2 2 2 " " Bottom 8 0 0 0 Uowfume- Wheat Closed Surface 10 ‘0 2 "4 75 " " Bottom 10 2 2 O " Open Surface 12 6 0 O " " Bottom 14 6 2 0 Corn Closed Surface 12 2 2 2 " " Bottom 2 2 O 4 " Open Surface 4 4 0 0 " " Bottom 10 0 0 0 Check Wheat Closed Surface 6 0 0 2 " " Bottom 4 4 O 0 " Open Surface 8 0 O 2 " " Bottom 20 2 0 4 Corn Closed Surface 4 6 2 O " " Bottom 4 0 O 4 " Open Surface 2 0 0 0 " " Bottom 6 0 2 O sH S S N o a a o o N o N S o soupom = = e S S S o N o o S N o o N o o Susanna ammo = SN N: N N s o a N S SH SH N 0 SN 0 soppom a = SH NS S a e N S SH 4 N a N s 3H 0 oommnsm SmmoHS q.SS NN S o N o o N o 0 SH .0 o S o o aoppom g = SN N S a o S S o N N S 4 SH N o oomanem ammo = SN N: N e a o NH SH 0 s e N S SN S soppom = = SN! om N a o N S s o N S S [m as o SSSMSsm SSSOHS among Sammwnmm m N N a o o S N S. N o N N o o soppom z = S N S N o o o S o a o o o N o mosupsm some = 4H Sm N N e o S m o o e N S SN 0 soppom = = NS S: S e a N NH SH N S N .s S SN S mosuusm ammoHS quoo SN N S N o S N o o S o N oH N a soppom = = SN 0 a a o o S S o N o S sH o a Susanna Sago = SN S: o N a o S S o a S o S SS 0 soppom = = mumm SN SH N N N o N o o S a 0 SH SH N Susanna SSSOHS pawns manages S S m S S m S S S S S S .S .S .m on SN SH 0 mpommdw H0 QOflWHmOQ mmenOHMm QHMHU Hwfihmpwfla mafiamppos QOHmeaasm pmpmm Sham SH 8mm mo S B Hmpoe wpommsa SSSS mo paoonmm QmmSSB mpmamnw u 0 Sam mmeSSn psoHM Smmsmcoo a o “mapmmn :flmum Smnpoopasmm a m. SH S S N S S S S S S S S S S S aoppom = c SH S S N S N N S S S S S N S N SSSSSSS mono = S NS S S S S S SH S N S S S SS N soapom = = SN NS SN S .S S S N S N S NH S SN N Sosansm SumoHS euoS SS S S S N S S N S N S S SN S S soupoS = = NH N S S N S S S S S S N S S N oomSpaS SSSS z SN NS N S S S S S 0 SH S N S SS S soppom = a SN SS N S S S S N S N S S S SS N SSSSNSS SSSSHS pawns souso SN SS S S S S S NS S S SS S SH SH S aoppom g 2 SH N S S S S S S N S N S S S S vomSuaS ammo = SH SS S S S N S S S N N N N SH S soppom = = NN SS S N S S S S S N N S NH NN S ooSSSSS SSSOHS apoo SS N N S N S S S S S S N SH S S aoppom = = SN S SH S S N N S N S S N NH N S mommpsm Sago = SN SS S S N S S S N S S S SH SS N soppom g = SN S S S N N S S N S S S SH S S SSSSNSS SSSSHS Swans oaSSBOS SH S S N S S N S N S S N S S N aoppoS = = SN N N S S S SH S S S N N S S S SSSSSSS SSSS = SN SS S S N S NH S S S SH S N SS S acupom = = SN NS N N N S S S S NH N S N NN N SSSSSSS SomoHS apoS NS S S S S S SH S N S S S SH S N aoppom = = SN S S S S N NH S S S N S S S N SSSSSSS ammo = NH NS NN N N S S S NH N N S N NN S soppom = = Snaprs SH S SH S N S S S S N N S N S S SSSSSSS SmmoHS Swans SNuoS S S S S S S S S S S S S .S .S .S SS SN SH S mpommflw .HO GOflMfimOQ mmwhmmmw CHMHO Hmfihmumfi SSNHSSHSE coprmHssm pmumm Sumo SH sum mo 0 9 Hmpoa mpommsw SSSS Mo pamonmm ' I All All! AdmfidflpGOOV m HHMSSB mummmpw n w Sum ”Sapmmp pzoau Smmdmcoo u o moapmwn aSSum Smnpooplsmm u m. SuSSScS Ho hpfiampuoa Goapmwfiadm nmpmw Sham Hmpoe mpoownw SSSS mo pnmonmm . ‘Il'l'llrlJ‘ ' .ll‘lu“!'l‘l'l'lu'l"l|lvlll'la'l'll- {'l‘l .' .0 il '1' ' l‘ ‘u I . 4' I‘llaullll 0'" I l. ’ II II I1 I'.‘|l\ l, 1" SH N SH S S N N N S N S N N S S aoppom = = S S SH S S S S N S S S N S S S SSSSSSS SSSS = S NS SN S S S S SH S S S S S S S soupom : = S N S N N S N S N S S N N S S SSSSSSS SSSoHS SSOS S S S S S S S S N S N N S N S aoppom = = NH S NH SH S S N S N S S N S S S SSSSSSS qoSS = SH S SN S S S S N S N S S S S S acupom = = S S SH N N N N S S S N S S N, S SSSSSSS SSSOHS Swan? SoonS N N SH S N S N S N S S N S S N aoppom = = S S N .N N N N N S S S S S S S SSSSSSS SSSS = N S. S N .S N S S S S S S S S S seppom = = N S S S S S S N S S N N N N S SSSSSSS SSSoHS SSoS S SH NH N S N N N S N S N N S S Eoppom = = N S S S S N N S S S N S S N N SSSSSSS nmSS = N SH S S N N S S N S N NV N N S aoppom = = SS N S SS S N S S N S S S S N S NH SSSSSSS SSSSSS among -SasSsop N N N N S S S N S S S S S S N soppom = = S N NH N S N S N N S S N N S S SSSSSSS SSSS = S SH N S N N N S S N S S S N S aoppom : = S S SH S S S N S S S S N N S S SSSSSSS SSSSHS SSoS Q ¢ 3 3 O O O O O N O O 0 ¢ ¢ Eoppom : : S N S S S N S N S N S S N S S SSSSSSS ammo = S S SH N S S N S S S S S S S N aoppom = = Snaprs S SH NH S S N N N N S N S S N S SSSSSSS SSSoHS Swans SNuoS S S S S S S S S S S S S .S .S .S SSHSHSOS SSSnopS SS NS SS SN oHSaSS So SNSS SHSSS HSHSSSSS AdmfinwunooV w mnmSS3 hpSQSpw n 0 Sam ”Saummp psoam Ummdmdoo n o "mapmmn cflmnm Smnpoopusmm n m. 9 E H. ' “I" IIH ||!| S S S S S S S S S S S S S S S aoppom = g S N S N N S S S S S S S S S S SSSSHSS SSSS = NH N SH S N S S S S S S S S S N aoppom = = S N S S N N N S S N S S S S S SSSSSSS SoSoHS S8S NH N S S S S N N N S S S S S S aoppom = = S N S S N S S S S S S S N S S SSSSSSS SSSS = SH S SH S N S S N S S S S S S N soppom g a SH S SH S S S S N S S N S N S N mommnsm SSSoHS SSSSS Scamp S S S S S N S S S N S S S S o aoppom = = S N S S S S S N N S S S S S N SSSSSSS noSS = S S S N S S S S S N S S S S S aoppom z = S S S S N S N N S S S S N S S SSSNSSS SmSoHS SSSS O N 3 O O N O O O O O O O N N Hoppom : = S N S S S S S S S S N S S S S SSSSSSS SSSS = S S SH S S S N S S N S S S S S aoppom g = SH S S S S N S S S N S N S N N SSSSSSS SmmoHS SSSSS maswsoo SH S SH S N SH S S S N S S S S S sogpom = g SH S S S S S S N S N N S N S N SSSSSSS ammo = S S S S N S N N S S S N S S S aoppom , a = N S S N S N S S S S S S S S N SSSSSSS SmSoHS qSoS S S N N S N S S S S S S S S S acupom = = N S N S S S S S N N S S S S S SSSSSSS SSSS = S S NH S S N S S S S N S S S N soppom = = Snaprs S N N N N S S S S N S S S S H SSSSSSS SSSSHS pmmna SN-SS S S S S S S S S S S S S .S .S .S muommflfl MO Hm 33 BM OM fiOfipHmom 0M¢HO#W CH6“? dehmpms mpfiampmoa qupSwSSDH nmpmw mama mamawm mo mama . c . Hmpoe muomwcw SSSS mo pnmopmm IHHI iJIIHIiH II ASoSSHpaoov S SASSB 36 after fumigation the total mortality ranged from 90 to 100 percent and 73 percent in the checks(TablelID. Ir:samples after 9 days(TablelJ) itummsfrom 93 to 100 percent with the checks remaining constant. In the samples 16 days after fumigation a mortality of 80 to 90 percent was re- corded in the treatments and 60 percent in the checks (Table 12). Table 15 shows that there were no noticeable residual effects on Indian meal moth larvae reared on samples of fumigated wheat and corn. In the second experiment, when wheat was dipped in emulsions of malathion and DOW-ET-l4 at the concentrations Of ten and 200 ppm, approximately 256 cubic centimeters of the emulsion was retained by the wheat. The actual amount or malathion and DOW-ET—l4 deposited on the grain was 1.5 ppm (emulsion 10 ppm) and 30 ppm (emulsion 200 ppm). The average amount of fumigants retained by the wheat, from the dipping treatments, was 250 cubic centimeters. The residual effects of various materials on adult saw-toothed grain beetles, confused flour beetles, and granary weevils reared on wheat dipped in the insecticides are shown in Tables 14 to 25. The exposure of saw-toothed grain beetles for one week to samples of wheat dipped in DOW-ET-l4»(2OO ppm) gave a 100 percent mortality through nine weeks after treatment (Table 14). In the tenth week the kill drOpped to 98 percent. No difference was ob- served between the effects of samples drawn from the closed TABLE 10 \N “J WEEKLY PERCENT MORTALITY OF CADELLES PLACED ON FUMIGATED WHEAT TWO DAYS AFTER FUMIGATION AND CONTINUOUSLY REARED Percent of dead cadelles Total Material Days after fumigation mortality of cadelles 9 16 25 50 57 44 Dowfume-75 10 2O 40 10 20 O 100 80-20 Mixture 10 10 13 50 2O 10 90 Dowfume EB-S O 10 20 2O 2O 10 80 Serafume IO 10 SO 10 3 O 80 Check O 10 50 30 O 0 7O WEEKLY P310 ENT TABLE 11 MORTALITY OF CADELLES PLACED ON FUMIGATED WHEAT NINE DAYS AFTER FUMIGATION AND CONTINUOUSLY TEARED Percent of dead cadelles -: t M Total Material Days after fumigation mortality of cadelles I6 25 50 57 44 51 Dowfume-75 40 10 50 13 IO 0 100 80-20 Mixture 10 50 10 20 50 0 100 Dowfume EB-S 10 20 20 50 10 0 90 Serafume O 50 10 20 20 10 90 Check 0 0 ‘ 0 50 20 20 70 TABLE 12 WEEKLY PE CENT NORTALITY OF CADELLEE PLACED ON FUMIGATED WHEAT 16 DAYS AFTER FUEIGATICN AND CONTINUOUSLY REARED Percent of dead cadelles Total Nkaterial ' Days after fumigation mortality of cadelles 23 30 57 44 51 58 Dowfume-'75 30 23 10 20 10 0 9o 80-20 Mixture 10 5O 20 20 O 10 90 ._-_‘ —- Dowfume EB—S 20 40 o 10 o 10 so Serafume 0 2O 5O 20 10 O 80 Check 0 10 o 20 20 10 60 W TABLE 15 PERCENT EMERGEICE OF INDIAN NEAL NOTH ADULTS F303 CULTURES OF LARVAE EXPOSED TC FUM GATE? WHEAT FOR FIVE WEEKS ( Total percentage of adults emerged . . Type of Material Grain storage Days after fumigation 57 44 51 58 Dowfume- Wheat Closed 40 5O 80 83 75 . Open 40 90 so 80 Corn Closed 50 5O 60 7O " Open 10 9O 4O 20 80-20 Wheat Closed 50 9O 5O 40 Mixture " Open 20 9O 50 #0 Corn Closed 0 60 5O 5O " Open 20 50 80 6O Dowfume Wheat Closed 40 70 9O 70 EB‘5 " Open 50 90 60 50 Corn Closed 50 60 20 4O " Open 10 80 5O 6O Serafume Wheat Closed 20 4O 6O 50 " Open 30 9O 4O 50 Corn Closed 20 50 50 4O " Open 20 4O 6O 40 Check Wheat Closed no 30 so 20 " Open 50 2O 40 0 Corn Closed 20 40 40 6O " Open 50 SO 60 40 41 N S N S N S N SH SH mono = N N S S N N S S S SSSSHS SSSSS . u u . NH NS SSH SS SSH SSSS = u u n u S SS SS SS SS SoSoHS HESS SHS SSHSSSHSS .. n I I 0 SH SH NH om ammo z u s u u N S SH N SH SmmoHS ASSS SHS SH-SS-SSS . u u SSH SSH SSH SSH SSH SSH SSSS : u u s SSH SSH SSH SSH SSH SSH SSSoHS ASSN SSNS SSHSSSHSS SS SSH SSH SSH SSH SSH SSH SSH SSH qoSS = SS SSH SSH SSH SSH SSH SSH SSH SSH SoSoHS ASSN SSNV SH-SS-SSS S SS NS SS SS SS SSH SSH SS SSSS = SH SS Sq SS SS SS SS SSH NS SSSSHS SESSSSSS S N SH S SH S SH SS SH SSSS = N N S NH NH SH S SS SS SSSSHS S-SS oasSsoS S N N S S S S SS SS ammo = S N S NH S N S SS NS SSSoHS SSSSSHS SNuoS S N N S S SH SN SS SS SSSS = N S SH SH S SH SS SS SS SoSoHS SSumasSaoS SS SS SS SS NS SS SN HN SH uaoEpSopp nmuum mama wwmwmmw Hmwnmpmfi Spoomcfl SSSS Ho pqoonom ZHmmezH mDOHm¢> Ed mmnHOHeommzH zH ammAHo B¢mmg OB mwdm zm>mm mom Dmmomxm mmqammm szmw Dmmeooelzdm mo MBHHdBmOE Hzmommm 3H wands 41 N S N S N S N SH SH Sumo = N N S S N N S S S SSSoHS SSSSS u u n . NH NS SSH SS SSH SSSS = u u n u S SS SS SS SS SomoHS HESS SHV SSHSSSHSS u n u n 0 SH SH NH om ammo z - u u u N S SH N SH SSSOHS HESS SHS SH-SS-SSS u u a SSH SSH SSH SSH SSH SSH ammo = u - . SSH SSH SSH SSH SSH SSH SSSSHS Saga SSNS SSHSSSHSS SS SSH SSH SSH SSH SSH SSH SSH SSH mono = SS SSH SSH SSH SSH SSH SSH SSH SSH SoSoHS HESS SSNS SHuSSuSSS S SS NS SS SS SS SSH SSH SS Sago = SH SS Sq SS SS SS SS SSH NS SomoHS Sesmmnmm S N SH S SH S SH SS SH Sago = N N S NH NH SH SS SS SS SSSoHS Summ SSSSSSS S N N S S S S SS SS SSSo = S N S NH S N S SS NS SSSOHS SnaprS SNuoS S N N S S SH SN SS SS ammo = N S SH SH S SH SS SS SS SomoHS SSumasSsoS SS SS SS SS NS SS SN HN. SH pamspmmnp nmpmm mama wwmwmmm HSHpSpSE mpoomcw SSSS Ho pamonmm ZH¢mw HmB mo Bzmfie¢mme mmamd mQ«>mmezH mDOHm4> 94 meHUHBommzH ZH QmmmHn 84mmg OB mwmm mom ommomxm mmqemmm zHmmezH MDOHm4> ad wmcHOHBOmmzH 2H GHAMHO Edam? OB mwdm zm>mm wom Ommomxm mQH>mwB %m¢z¢mw ho WBHAmmezH wDOHmAEV 94. mmOHoHBommzH 2H QMSHSHHQ wMHBBmm MDOHR Dmmbmzoo MO NBHQBNJS BZMOMMH ma Mflde 44 .Hfibmma hnmcmnw n o “mapmmn Hdoam Ummfimcoo u o «maummn dflmuw UmnpOOpIme u m. 31!; HN oH NN H H m m N N 3 N ¢ 0 N o N 0 0H mono = ¢N mN @N 0H 0H NH 3 N ¢ ¢ oH N o o o o o m ammOHo Homgo ooH mm 00H 0 ¢ 0 o a o o o o N H o No :¢ ooH ammo Hagm oHV No ¢m 00H 0 ¢ 0 N o 0 0H N N 3H 0H N on oN mm cmmoHo aOanmHma Nm OH ooH mH N 0 ON ¢ N o N m m NH N N m om amao Hang oHv mm in m: 0H ¢ o NH 0 0H N 3H ¢ ¢H oH N NH HH NH ammoHo ¢Huamuaoa ooH ooH 00H 0 o o o o o o o o o o o ooH ooH ooH ammo Hang OONV 00H ooH 00H 0 o o o o o o o o o o o ooH ooH ooH ummOHo aOanmHmH noH ooH 00H 0 o o o o o o o o 0 é o ooH mm 00H ammo Aagg OQNV ooH ooH 00H 0 o o o o o o o o 0 3H 0 ooH mm ooH comOHo NHuemugoa 00H :m 00H 0 o N o o o o :H o o ¢N ¢H 00H :3 :m ammo = ooH 3N 00H 0 m o o m a 0 ON N N NN oH No NN Nw omono masmmgom ooH 00H 00H 0 o o 0 ¢ m N Na om :m mN oH ¢¢ NH oH ammo mumm ooH noH 00H 0 N o o o o o Nm N Nm oN NH mm #m an ammoHo oasmsoa ooH mm mm 0 ¢ 0 o s o N #m o :m mN mH :m m om ammo ops» 00H :0 :0 o o w o o N o Nm N mm NN NH N: N Na womOHo ust 0N:om No o¢ am 0 o o o m N N NH N :u ¢ ¢N NN : om amao = mm mm om o N o o H o 0 mm 0 mu m mN NH 3 :m ummOHo mu-masHsoo 0 O m G O m G O m 0 O m w 0 w .0 .0 §m mxmmg mpHN N: mm NN HN ¢H nmpmw mpoomnw pnmapmmnp pmpmw mhwn memmwm Hmflpmuus mo mpHHmppoe pros if mpommcfi ”Now go pamonmm HHHHHHHHHHHHHHHHHHHHHHHHHH“HHHHHHHHHHHHHHHHHHHHHHN mmNNmm Humposzazoo az< Bamaamm mmoHoHeommzH 2H mmmmHn a4mma zo amoNNB humcmnw « n mmeNNn HSOHH Ommsmnoo n o ”NHpNNp cfimnm Nonpooptswm u m. 5 NO ON ON N N NH N N N NH N N N N N Nm O OH ONOO = NH NH NO N N NH N O NH O N N N N N N O N ONNOHO NONOO NO Nm OOH . u u N O O N N O N N OH ON NN OO ammo Hang OHN NN NN OO - u u N O N N N N NH N N ON ON NO NONOHO NOHONNHNN NO NO NN . u u N N N N N NH NH NH N NH ON NH ONOO Hana OHV NN NN Nm . - - N N NH NH N NH ON ON O NH NH N NNNOHO NHuemugOO OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONOO AaOO OONV OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONNOHO NOHONNHNE OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONOO HEOO OONV OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH NNNOHO NHuem-2OO OOH NO OOH O N O O N O O N O O NH O OOH N OOH NNOO = OOH OOH OOH O O O O N O O N O O NO O OOH NN OOH NNNOHO NasNNONN OOH NO NO O N N O N O O Nm N NN NN NH NO N NN ammo NnNN OOH OOH NO O O O O O O O N N NO NN NH NN N ON ONNOHO NasNBOO OOH OOH ON O N N O N N N ON N NN NN N NO N Om OOOO was» NO NO NO O O N O N N N NN N NN ON N NO N NN OONOHO -st ONuON NO NO NO N N N N N N N NN N Om N N NO NN NO ammo = NO OO OOH O N O O OH O N NH N NN NO N NO N NO OONOHO NO-NaaNBOO O O N N O N O O N O O N N O N .O .O .N wxmos N>wm m: Nd mm mm Hm NwNHOpm Hwanoumfi nwmepmwmwmww pnmapwmnp nmpwm mhda No Name . proe Npommafi ONNO mo pqmonmm .. m MHHmDODZHBZOO Q24 EZHEBamB mmad mugs” #H >44 meHOHBOHmZH WWWMWMHHHD Edam? ZO DHOfiHnH WBOHmZH ho NBHHfiuMOE Barfltmfinm MHMWHE ma Manama 46 .HH>NNB hpchpo u o mmemmp pfioam Ommdmuoo u o “mapmmn nflmnm Umnpooplsmm n m. N NN NN O N N O N OH O N N N N N N N N NONO = NN NH NN O O N N N NH N O N N N N NH N N ONNOHO NONNO NN NH OOH . u u u u u N O O N N O NO OH OOH ONOO OOOO OHO NO NN NO - - n u u g N N N N N N NO NH OO ONNOHO OOHONNHNN NN NH N - - - u - I N O N NH N N N NH NH NOOO OEOO OHN OO ON OO - u u I - - N N N NH N OH OH NH NH ONNOHO NHsemuaoO OOH OOH OOH . u u O O, O O O O O O O OOH OOH OOH OOOO OOOO OONN OOH OOH OOH - - . O O O O O O O O O OOH OOH OOH ONNOHO OOHONNHNN OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONOO OEON OONV OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONNOHO NHuem-NOO OOH ON OOH O O O O O O O OH O O N O OOH N OOH ONOO = OOH NO OOH O N O O N O O NN O O NH N OOH NN NO ONNOHO NestuNN NO NO NN O N O O NH N N OO N NN OO N NO N NH NOOO Onmm OOH NO NO O O O O N N N NO N NH NN N ON NH NO ONNOHO NastOO OOH OO NH O N N O NH N N NH N NH NO N NO NN N ONOO ops» OOH OO NN O N N O N N N NO O NN NN O NO NH N ONNOHO -tz ON-ON OO ON ON O N O N N N NH NH N NH NH N ON N ON ONOO = NO NN )N O O O O O O N NO OH N N N NN OH NO OONOHO OOumasNaOO N O N O O N O O N O O N N O N .O .O .N Nxmms N>HN NO ON NN OO NN umpmm mpommqfl pnmapmmnp pmpmw mhmn WWNMMMM HNOprNE mo mpflampnoe proa ONNNNN NHNOO NNOHOHOONNZH zH ONNNHO 94mm; 2 NpONNaH ONNO HO OOOOuNm 0H flfimde DZHBZOO 024 BZMEBdmmB mmam< wHNN3 Opmcmpo u w “NHNNND macaw ONNSMQOQ n o "NHpNNn CONNN OmnpOONIBNw n m. NO Nm NO OH N N N NNuw m NN NH N N N OH O O mmOO = ON NN NO NH O N N OH OH NH NH N N N N NN O N OONOHO NONOO NO OH NN - u u - u u u u s OH N NH NN N NO OOOO OaOO OHO NO NH ON . u - n u u u n . NH N N ON N NO OONOHO OOHOOOHNO ON NH NN . - - u u u n - u N N OH NH N NH ONOO OaOO OHV NH N N u u u u u - n - - N N N OH N N ONNOHO NH-ON-OOO OOH OOH OOH . u - u n n O O O O O O OOH OOH OOH ONOO OaOO OONO OOH OOH OOH . u - u u - O O O O O O OOH OOH OOH ONNOHO OOOOONHON OOH OOH OOH O O O O O O O O O O N O OOH NO OOH NOOO OOOO OONO OOH OOH OOH O O O O O O O O O O NN O OOH NO OOH ONNOHO NHneNugOO OOH NN OOH O N O N NH O OH NH O NO OO N NN N NO ONOO = OOH NN OOH O N O N N N N N N NO OO O ON N NO OONOHO NOONNONN OOH NO NH O N N N NH O N NN N NN NN OH OH O O ONOO OnNN OOH OO NO O OH NH O NH N N NO N NO ON NH NN O NH ONNOHO NONNOOO OOH NN NO O N NH O NH N N NN N ON NN O NH N N ONOO ops» OOH NN OO O N NH O OH NH N NH ON NO NO O ON N N ONNOHO -st ON-ON OOH NO NO N N N OH N N N NH N NO NN N N N NH NOOO = NO ON NN O N N N NH N N ON N NN NH NN N N NH OONOHO OOnmastoO O O N O O N O O N O O N O O N .O .O .N NxNNB Nbfim mm mm m: Nd mm Hmpmm Npommnfl pQNENNNup anHN mama WWNMMMM HNOHNNNS Ho Opfiawpnoa Hmpoe Npommcfl ONNU mo unmonmm nmmdmm MAmDODzHBZOo 02¢ azmsa4mme mmemd mMNNB mudnwuo u o ”Napmop pdoam @dehnoo a o "mapmmn dfimnm cmnpooplamm u m. OO NN NH N N N NH N N O OH O N NH O OH NH N NOOO a NO OO NH N N N NH N N N NH N N ON N O N N ONNOHO NOOOO N O NH I I I I I I I I I I I I N O NH NNOO OEOO OHV O O N I I I I I I I I I I I I O O N ONNOHO NOHOONHON ON O O I I I I I I I I I I I I ON O O NOOO OaOO OHV N O N I I I I I I I I I I I I N O N ONNOHO NHIONIOOO OOH OOH OOH I I I I I I I I I O O O OOH OOH OOH ammo OaOO OONN OOH OOH OOH I I I I I I I I I O O O OOH OOH OOH ONNOHO NOHOONHNE OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH NONO OOOO OONV OOH OOH OOH O O O O O O O O O O O O OOH OOH OOH ONNOHO NHIONIOOO OOH NO OOH O N O O N O N N O O NH N NO NN NO ONOO = OOH ON OOH O N O O N O O N N N N NH NO NN ON OONOHO NEONNNNN NO NO NO O N N N NH NH OH NH O NH NH O OO NN NH ONOO OINN OOH NO ON N N N N N NH NH NH OH N OO NH NO NO NH OONOHO NOONBOO NO NO NH N N N N N N ON ON N ON NN N NN NN N NOOO was» NO NN NN O N N N NH N NH NH N NN NN N OO NN N ONNOHO Itz ONION NN NN NO N O N N N NH NH NN N NN NH N NO NN N OOOO = NO OO NN O N N N N NH NN ON N ON NH NH NO ON N ONNOHO OOIOasNOOO O O N O O N O O N O O N O O N .O .O .N w 003 0>H umpwm NOOOOWH OO ON OONBONMMO ONONN NMMO NN Mwmwmmm HNHNNONN Ho mpOHNppoE HNOOO QWQHOHBOHQZH ZH DHHfiHD Edam? Npomwnfi ONNO mo ammonmm ONONNN NANOoszazoo 924 OZNEONNNO ONONN NOON OO 20 ONONQN NOOwNzH mo NquNamoa azmommm qummg HN HHQ¢B 49 .HO>NNB Opmcmpo n o ”mapmmn nsoaw Omwdwdoo n o ONHNNNQ campw OmspOOplsmm n m. "l| |l11 NN OO N N N O N N O N NH N N N O ONOO = NN N NH N N N N N OH OH N O N N O ONNOHO NONOO NO ON OOH I I I I I I I I I NO ON OOH NOOO = NO OO OOH I I I I I I I I I NO OO OOH ONNOHO OaOO OONO NOHOONHNN OOH OOH OOH O O O O O O O O O OOH OOH OOH NOOO g OOH OOH OOH O O O O O O O O O OOH OOH OOH ONNOHO OENO OONN NHIONINOO OOH NO NO O O N O O N NN OO NH NO N NN NOOO : OOH NO NO O N N N N N N NO NH ON NH OO ONNOHO NastNNN NN NO N N OH O NH NH N ON NN O N N O NOOO = OOH NO ON O N N O NH N NO NN OH NN ON NH ONNOHO OINN NOONBOO NN NO N N OH N N NH N ON NN O NH N O NOOO = NO NN NN N NH N N OH N NO ON N NH NH NH OONOHO Ogsuxfiz ONION NO NN N N N N NH N N NO NN N ON NH O NOOO = NO NO OO N N N N N N NN NO OH N NH OH ONNOHO OOIoastom G U m w 0 w 0 O m 0 O m .0 .0 cm mxmoa much on mm mm 03 ammuopm uopmm Naommnfi namepwmnp umpum thn mo Name HNONNPNE mo OpOHanOe proa ‘1'."t‘} - NpONNcO ONNO mo pamopom lull I". "l’ III ‘Ilrll 'Ill' :0. I- II'I.‘||'\|I‘I|III.IOI -- ‘. I'.|l'11| ' .. ‘vIIIOI {illl .0. Il'lllll ID- I -‘1 .| I‘ll! 'IIIt ' I’.I‘.l|o'nl|l {It Qmmdflm MHWDODZHBZOO 02¢ Ezwfiedflma mm8m¢ mhdn Ni wmQHOHBOHQZH zH DmthQ 84mm? 20 QfioNN3 OH N N N N N N N N O N N NNOO = N NH N O N N N N N N N O ONNOHO NONOO OOH OOH OOH O O O O O O OOH OOH OOH NOOO = OOH OOH OOH O O O O N O OOH NO OOH ONNOHO OOOO OONV NHIONINOO NO OO OO N N N N N NH NN NH NO NOOO = NO NH NO N N N N N N OO ‘ NH NN OONOHO NOONNNNN NO NO NH N NH O NH NO N NO N OH NOOO = NN ON NH N NH N N NH N NO OH N ONNOHO OINN NesNaOO NO NN N NH N N ON NH N NO N N ONOO = NN ON O NN , N NN N N NH N N OONOHO NNNONHN ONION NO NN N NH N N NN N N NO N N ammo = NO NN NH NH N N ON N N NN N OH ONNOHO OImasNOOO O O N O O N O O N .O .O .N > .\ .fiMMWWWuMMMMW mt m0 . om NmNpMMm HNOpmpmz NOONOHNNNOB pqmapmmpp nopmm NOON no N B HOOOO NpONNnO ONNO HO pnmonmm g nmmdmm MHQDODZHBZOO On< Bzwfie¢mme mmemd mwdo 03 I meHOHBonzH 2H memmo 848$? 20 QMO¢Qm meommzH mo MBHHdamoa Bzmommm wgmmaa mm mnmda Opmqmno n o Nam ”Napmmn mdoam ONNsmcoo u o ”Napmmn .HO>NNB nfimnm OmnpOOpngmw u m. NH N N N N N CH N N amao = N OH N N N O N N N ONNOHO NOONO OOH OOH OOH O N O OOH NO OOH NOOO = OOH OOH OOH O N O OOH NO OOH ONNOHO OaOO OONO NHIONIOOO NN N NO NH N OH NO N NN NOOO = NO OH ON NH N NH NO N NN OONOHO NesNNNNN NN NH N ON N O NN OH N ammo = NO NH N NN N N NN OH N OONOHO OINN OsstoO ON N N NH N N NN N N quO = NN NH N NH N O NN N N ONNOHO NNNONHN ONION NO OH N NH N O ON N N ONOO = NO N N NH O N NH N N OONOHO OOINONNBOO O O N O O N .O .O .N m ONE 03 on no mmmno N nmpwm Npomwcfi ncmapmmnp pmpmm NONQ mo NAME Hmfipmpms Ho hpfiampnofi Hmpoe Npoommfl ONNO mo pdmonmm Qmm4mm MHmDODzHBZOO Dz¢ Bzméedmme mwem4 mw‘1’Stonand Nagner (1941), Farrar and Flint (1942), and Wailkden and fichwitzgebel (1051), when they used a 5:1 mix- tUJ?e of ethylene dichloride and carbon tetrachloride. Walkden and Schwitzgebel (1951) also reported that the 4:1 miD‘Eture of carbon tetrachloride and carbon disulfide, “”1i42h is comparable with 90-20 mixture, was a satisfactory fumigant used at the rate of two gallons per 1000 bushels. I" 61 The mortality resulting from the exposure of the second set of insects to the fumigated wheat and corn in- dicated that some of the vapors of the fumigants were re— tained in the grain, though not in high concentration. In the drums which were left Open the retention of the fumi- gant vapors were less than in the closed drums. Dowfume 38-5 was retained in the highest concentration, while Dow- fume-75 and 80-20 Mixture dissipated most rapidly. This retention of fumigant vapors in the fumigated grains Was also noticed by Nalkden and Schwitzgebel (1951). They observed that the 1:4 mixture of carbon disulfide and carbon tetrachloride (similar to 93-20 Mixture) was re- tained in lethal concentrations for two to four weeks in 1000 bushels of wheat. Similar results were obtained when a 3:1 mixture of ethylene dichloride and carbon tetra- chloride was used. The time of retention increased with the increase in the amount of wheat. The short period of retention in this study was possibly due to the small quan- tity of grain fumigated. The reason for the total absence of the emergence of adult confused flour beetles from the wheat flour contain- ing its eggs, larvae and pupae, could not be ascertained. The conditions to which these insects were exposed were the same as those of the stock cultures and there was no sign of a mass mortality of the immature or adult stages. No parasites were found and no exposure of checks to any harmful vapors was recorded. 62 When saw-toothed grain beetles, confused flour beetles and granary weevils were fed on fumigated wheat and corn, little mortality occurred. Results were similar when Indian meal moth larvae were reared on the fumigated grains. Slight residual action was indicated in the case of adult cadelles which were exposed to grain fumigated with Dowfume-75. “ When large quantities of grain are fumigated, the grain at the exposed surface becomes saturated with the fumigant. It is in this grain that the greatest concentra- tion of insects occur. In this experiment only two bushels l of wheat and corn were used in each drum and the amount of fumigant used was not sufficient to wet the surface layer of grain as in the normal fumigations. To overcome this difference a second series of experiments was set up, in which wheat was dipped in the fumigants. This time, DOW-ET—l4 and malathion were also used at the concentra- tions of ten and 200 ppm. When saw-toothed grain beetle,.confused flour beetle and granary weevil adults were reared on the wheat treated in this manner, residues of the insecticides were noted in the Wheat. Lethal concentrations of DOW-ET—14 (200 ppm, actual DOW-ET-l4 deposited on the wheat was 50 ppm) were retained for ten weeks after treatment. At the concentration of ten ppm (actual DOW-ET-l4 retained by the 63 wheat was 1.5 ppm) it did not leave enough residues to be of any practical value. Malathion (200 ppm, actual amount of malathion de- posited on the wheat was 20 ppm) residues were responsible for 100 percent mortality of saw-toothed grain beetles for seven weeks after the treatment, at which time the study was terminated. Malathion residues did not show any signs of decline at the end of this same period. Residues left from the ten ppm (actual malathion deposited on the wheat was 1.5 ppm) treatments were effective against saw-toothed grain beetles for the first three weeks, with the mortality gradually declining. Serafume dipping treatments gave the highest resid- ual effects among the fumigants used, when evaluated for the control of the saw-toothed grain beetle. This material provided a high mortality for the first three weeks. Dow- fume-75 and Dowfume EB-5 provided residual activity to a lesser degree. In the case of granary weevils, malathion and DOW-ET-l4 (200 ppm) treatments were effective for a period of six and ten weeks, respectively. DOW-ET-l4 at the con- centration of ten ppm was not satisfactory, while malathi- on at the same concentration was effective for at least two weeks. Lindgren, Krohne and Vincent (1954) also ob- tained residual effects from the malathion treatments at concentrations as low as two ppm. They reported that this 64 residual activity lasted for about three months. They also observed that there was no reproduction of rice weevils, granary weevils and the lesser grain borer in the treat- ments. These treatments killed all of the adults for a period of four months. In this investigation no reproduc- tion of saw-toothed grain beetles, confused flour beetles and granary weevils was noted. Serafume and Dowfume EB-5 were effective against the granary weevils for about three weeks. Malathion and DOW-ET-l4 (200 ppm), when evaluated against the confused flour beetles, were retained in lethal concentrations for six and nine weeks respectively. The same chemicals at the concentration of ten ppm were not effective in their residual action. Serafume, Dowfume- 75, Dowfume EB-5 and 80-20 Mixture provided little residual activity in the case of confused flour beetles. It was observed that as the time passed the effectiveness of the various insecticide residues gradually declined and van- ished completely after a certain period of time. Emergence of the Indian meal moth adults from larvae reared on the wheat treated with DOW-ET-l4 (200 ppm) in- dicated a residual activity for three weeks from this treatment. None of the other materials showed residual action of practical importance against this pest. Certain irregularities in the data may be due to experimental errors. In Table 15, which gives the mortal- 65 ity of granary weevils exposed to dipped wheat for seven days, it is seen that the mortality of the weevils declined gradually with the passage of time. However, in the samples taken 55 days after dipping and counted 42 days after the treatment, a sudden rise in the mortality was noted. In the next week's samples the mortality declined as usual. Similar observations were made in Table 16 in the samples taken 55 days after dipping; here the checks also showed an upward trend in mortality. In Table 14 this rise of mortality occurred in t.e samples taken 49 days after dipping and mortality recorded 56 days after the treatment. Again it was noted that the emergence of Indian meal moth adults, from samples taken 55 days after dipping and later, started declining and finally no adults emerged. Various possibilities were considered, in order to C)” discover the reasons for this irrefularity. One possi i1- ity which may have caused this irregularity appeared to be an Aramite treatment made six weeks after dipping treat- ment to clean up a mite infestation in the rearing room. Care was taken to air the room thoroughly before the cul- tures were returned to the room, but apparently toxic va- pors were still retained in sufficient quantities to af- fect the mortality of the insects. Saw-toothed grain beetles were the least affected, while the granary weevils were most susceptible. It also had an adverse effect on 66 the Indian meal moth larvae. A second Aramite treatment in the beginning of the third week of September ( two weeks later than the first) likewise accounted for the second rise in the mortality of insects. The Indian meal moth was especially susceptible, as all of th larvae were killed. . From the germination studies of wheat, corn, rye, barley, oats, and kidney beans, before and after the fumi- gation, no harmful effects were observed on the seed ger- mination from the treatments. Roark and Cotton (1328} also presented the same results when they tested various ali- a phatic chlorides. Cotton (1944) observed that a 5:1 mix- ture of ethylene dichloride and carbon tetrachloride did not affect germination of grain, regardless of its dosage, period of exposure and the moisture content of the seeds. SUMMARY AND CCNCL’S ONS This study was established to investigate the re- sidual activity of some of the common commercial fumigant mixtures. Two bushel samples of wheat and corn were fumi— gated and stored under conditions comparable with those in Open and closed farm storages. Saw-toothed grain beetles, confused flour beetles, granary weevils and cadelle adults, as well as Indian meal moth larvae were exposed to samples of fumigated grain weekly and the resulting mortality ob- served. The initial results indicated that,when small samples were fumigated, the results were not comparable with those that exist on the surface of large quantities of fumigated grain. In order to simulate these conditions as closely as possible, samples of wheat were dipped di- rectly in fumigants, as well as in emulsions of malathion and DOW-ET-l4. Again, adult saw-toothed grain beetles, confused flour beetles and granary weevils, and Indian meal moth larvae were eXposed to the samples of the wheat. The results from these studies are outlined as fol- lows: l. Dowfume-75, 90-20 Mixture, Dowfume EB-5 and Serafume proved to be highly efficient fumigants for con- trol of saw-toothed grain beetles, confused flour beetles and granary weevils. 68 2. Little residual activity was apparent when these fumigants were used to fumigate two bushel samples of wheat and corn at recommended rates. 5. When wheat was dipped directly into the emul- sions of malathion and DON-ET-14 at a concentration of 200 ppm (50 ppm actual residue on the grain), effective resid- ual action was evident for seven to ten weeks against saw- toothed grain beetles, confused flour beetles and granary weevils. DOW-ET-l4 was also effective against Indian meal moth larvae. 4. malathion at ten ppm (1.5 ppm actual residue on the grain) had an effective residual period of three weeks against saw-toothed grain beetles and granary weevils, but provided little control of the confused flour beetles. DOW-ET-14 at ten ppm was not effective against these same pests. 5. When wheat was dipped directly in the commercial formulation of Serafume, its residues were effective for the control of saw—toothed grain beetles and granary wee- vils for three to five weeks, but had very little effect on confused flour beetles. 6. Dowfume EB-5 was slightly less effective than Serafume in its residual action on the above insects. 7. Dowfume-75 and 83—20 Mixture had little resid- ual activity against the insects tested. 69 8. None of the materials used in this study,with the exception of DCB-ET-IQ (200 ppm),provided significant residual action against Indian meal moth larvae. 9. Germination of wheat, corn, barley, oats, rye and kidney beans was not affected by the fumigation with the recommended dosages of Dowfume-75, 80-20 Mixture, Dow- fume EB-S and Serafume. .! LITERATURE CITED Back, E. A. 1920. Insect control in flour mills. U. 8. Dept. Agr. Bul. 872. 40 pp. ' Back, E. A., and R. T. Cotton 1925. 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