I ,«TATE PLANT BO.' E-521 January I9UI United States Department of Agriculture Bureau of Entomology and Plant Quarantine METHYL BROMIDE FUMIGATION OF IMPORTED PERISHABLE POOD PRODUCTS By Randall Latta, Division of Control Investigations INTRODUCTION During the winter months of 193&» 1939. snd 19*40 large quantities of perishable food products imported into this country were fumigated with methyl "bromide for the destruction of certain insect pests. The results of these treatments, some of which themselves provided the experimental data, upon which recommendations for treatment were "based, are presented herewith. Commercial fumigations were performed princi- pally at New York, N. Y., or Havana, Cuba, with a few at Seattle, W^sh. Supplementary experimental tests were made at New York, Havana, San Juan, P. R. , and Washington, D. C. The following food products were treated: Green pod vegetables , including green lima "beans, string "beans, and pigeon peas (gandules); cipollini "bulbs ( Muscari comosum ) , chestnuts, grapes, and poaches. The experimental tests were all made by the writer, with the aid and cooperation of foreign-plant quarantine inspectors, various importers, the Seccion de Sanidad Vegetal de la Secretaria de Agricultura de Cuba, and the Asociacion de Cosechoroe y Exportadores de Frutas y Vegetales de Cuba. The Cuban-American Terminal Company of Havana, Cuba, also cooperated in experimental studies made in a fumigating plant they erected at Havana. Ma?: Kisliuk, Jr., in charge of the New York office of the Division of Foreign Plant Quarantines, and Herman G. Frank, inspector in that office, gave invaluable aid in the performance of the tests, as did W. A. McCubbin, in charge of the San Juan office of the same division, and others. C. A. Reed, of Nut Investigations, Division of Fruit and Vegetable Crops and Diseases, Bureau of Plant Industry, assisted in examining chestnuts for quality following fumigation. The Division of Forest Pathology, Bureau of Plant Industry, provided chestnuts for studies of the effect on quality and insect control. - 2 - GHEEN POD VEGETABLES Problem Green pod vegetables imported into the United States during winter months from the West Indies (Cuba and Puerto Rico) have frequently been found infested with larvae of Maruca testulalis , a bean pod borer occurring throughout that area but not known within continental United States. Cuban green pod vegetables wrre formerly examined in Havana by inspectors of Sanidad Vegetal, and reexamined by inspectors of the Division of Foreign Plant Quarantines upon arrival at New York. This method was of doubtful efficiency. Accordingly, in the 1938-39 shipping season shipments in which any infestation was discovered were refused entry. This caused losses to importers, as some infested shipments were found each week, and also raised the qupstion as to whether inspection was a sufficient safeguard, since the occurrence of live larvae in some of the shipments each week would indicate that all shipments might be lightly infested. Insect-Mortality Studies An arbitrary selection of * dosage calculated to be high enough to' cause complete mortality of all Maruca testulalis larvae at dock temperatures w^.s made on the basis of previous experience, and a test fumigation was m?dc with infested shipments of green lima beans after preliminary trials had shown this product to be uninjured by treatment. The dosage, rate chosen was k pounds of methyl bromide per 1,000 cubic feet of sp^cc, including the load, for a period of 90 minutes in a partial vpcuuh of 15 inches, sustained for the duration of the treat- ment.!/ The beans wore made available to the Bureau for experimental studies by importers in an effort to salvage th^ shipments. After fumigation a number of hampers of beans were reinspected, snd when no live l?.rvac were found the beans were considered free from hazard and allowed entry. The siuae experimental procedure was followed for infested ship- ments discovered each wc-k from December 6, 193S, to the end of the shipping; season on April I9 , 1939. The mortality of larvae, as shown by the examination of shipments after fu-.-.igation, is given in table 1. All examinations were made within 2k hours. — For the sake of clearness and brevity, dosage rates are herein- after abbreviated similarly to the following: k lb. for 90 nin. in a 15" vac. All dosages are in pounds of methyl bromide per 1,000 cubic feet of sp^ce. - 3 - Previous experience yith methyl bromide fumigation had shown that insects night live several days after exposure before succumbing. There- fore, when mortality occurred within 2h hours it was assumed that the treatment was well over the minimum dosage needed. Table 1.— Mortality of Maruca testulalis larvae in lima bean pods resulting from 90- n inute fumigations with nethyl bromide at the rate of k pounds per 1,000 cubic feet in a 15-inch vacuum, at dock temperatures, New York City, 1933-1939 Tempera- Number of Number of larvae ture hampers T — a 771 — Mortality Bate of pods, JSSd ""* AllTC ' Percent "F. Dec. 6 51-57 1+0 30 100 lU 1+1-1+5 1+3 16 100" 21 1+0-1+5 21 1 100 28 50 11 3 100 Jan. 1+ 1+0-1+3 33 5 100 11 50 29 90 100 18 38 l6 2 100 25 3^0 37 70 100 In February and March, 1939» further studies wore" made at San Juan, P. R. , where an abundance of Maruca testulalis larvae were available. The results of these and the above-mentioned tests have been published^/ and will be considered here only briefly. Vacuum fumigations at temperatures between 75 ° and 85 °. — Low dosages were found to be effective under vacuum conditions, as a rate as low as O.5 lb. for 90 min. in a 15" vac. gave complete mortality, even in the centers of packed crates (see- table 2). Atmospheric fumigations at temperatures between 75 ° and SO .— A 2-hour exposure at atmospheric pressure proved to be as affective as a 90-minute exposure in partial vacuum. A dosage as low as O.5 lb. for 2 hr. at atmospheric pressure produced complete mortality. t Vacuum fumigations at temperatures below Z9_°.--A higher dosage was necessary at, the- lower temperatures. Survivals occurred after exposure to 1.5' lb. for 90 min. in a 15 M , vac. at . Ul°, but 2 'lb. at 55° and 2.5 lb. at 1+1° gave complete mortality in one test each. (Table 2.) ■2'Latta, Randall. Methyl bromide fumigation for destruction of pod borer larvae. Jour. Econ. Ent. 33 (l): 176-179. I9U0. Table 2. — Mortality of Maruca t cstulalis larvae in string beans resulting from 90- Qinu *G fumigations with methyl bromide in a 15-inch vacuum, San Juan, P. H., February 1939 Dosage Te^pera- ( pounds per 1,000 turo cubic feet) °F. Number of larvae Dead Jive Mortality, percent Normal temperatures 0.25 0.5 0.5 0.5* 1 1* 1.3 1.5 2 2 2.5 3 1 1 1 1.5 1-5 1-5 2 2.5 80 80 80 77 80 77 77 78 80 77 82 SO Ul Hi kl kl kl kl 55 Ul 11 22 23 51 23 71 15 ^5 29 11 18 Low temperatures 30 kk 6 Si • 36 22 2 3 2h 1 3 69 100 100 100 100 100 100 100 100 100 100 100 91 100 20 S3 100 82 100 100 ♦Infested beans layered in the center of 9 loaded crate.' Later tests at Havana, Cuba, in December 1939 substantiated the results obtained at San Juan. These tests were made in an atmospheric fumigation vault (2,500 cubic feet capacity) as follows: O.5 lb. for 2 hr. at 70-80°, empty vault— 31 larvae, all Aead. 1.5 lb. for 2 hr. at 70°, loaded hampers in empty vault — 90 larvae, all dead. 1.5 lb. for 2 hr. at 70-80°, pods in exposed position in partially loaded vault — 12 larvae, all dead. 1.5 lb. for 2 hr. at 70-80°, loaded hampers in center of loaded v»ult — k larvae, all dead. 1.5 lb. for 2 hr. at 70-80°, pods in exposed position in fully loedod vault — 13 larvae, all load. - o - Host-Tolerance Studies Green lima bj^ans. — At New York City small lots of Cubnn ling beans were funigated v;ith nethyl broni'd'e without injury, as listed in t~blc J>. These beans had been picked at least a week previously but had been under good storage conditions (5O F. or less) during the intervening tine. The lots treated on November 30 were held in sterile and shown "n December 5 to 1 committee of bean importers, who were unoble to ' istinguish between fumigated and untreated samples. Table 3«— Results of experimental fumigations of green lima beans at New York City, 193S Treatment D=ite Dosage, Duration, Vacuum, Temp., Results pounds minutes inches °F. Nov. 11 Nov. 30 2 90 15 70 No injury 2.5 90 15 • 70 Do. 3 90 15 70 Do. k 90 15 70 Do. 2.5 120 none 70 Do. 3 90 15 >43 Do. k 90 15 h3 Do. 5 90 15 ^ Do. k 90 25 ^3 Do. At San Juan small lots of Puerto Rican green lima beans (freshly picked) were treated without injury, as shown in table U. One-half of e.^ch sample was stored at room temperature, the other half in sn electric refrigerator. Some of the beans fumigated March 3, as listed in table H, wore shipped to New York City, then transported to Washington, D. C, where they arrived in good condition. An additional series of lima beans fumigated with 3-lb., U-lb., and 5-lb. dosages were sacked in tight paper bags soon after removal from the vault and stored in a household electric refrigerator. After 5 days they were s.pparently in good condition, but upon removal from the refrigerator they decayed r?.pidly. This was assumed to be due to failure to allow the pods to aerate well following fumigation brfore they were placed in the tight bags. The experiment was repeated, cheesecloth bags being used, and no injury occurred. At Havana, Cuba, l6 hampers of freshly picked lima beans were fumigated, without other load, with 1.5 lb. for 2 hr. at atmospheric pressure at 70° on December 3, 1939. After firing, the beans remained in excellent condition for 8 days at precooling temperatures. - 6 - Table k. — Results of experimental fumigations of green lima beans at San Juan, P. ?.., 1939 Treatmen - b Date Dose.go, Duration, Vacuum , Temp. , pounds minutes inches °F. Storage Results Feb. 2k 1 90 15 75 room refrig. No injury Do. 2 90 15 77 room rcfrig. Do. Do. 3 90 15 80 room refrig. Do. Do, k 90 15 S2 room refrig. Do. Do. 5 90 15 82 room rcfrig. Do. Do. Mar. 3 2 90 15 77 refrig. ship* Do. Do. ♦Shipped to New York. String; berns . — At San Juan, P. R. , several tests were made with freshly picked string beans, as given in table 5. ^ n onc series a half of each sample was stored at room temperature, the other half in an electric refrigerator. In these tests increasing amounts of injury to pods were caused 'by dosages of 3 lb. and above, but with 2 lb. only very slight injury was caused in two trials, and none in two others. Two lots treated with 2 lb. were shipped to New York and arrived in excellent condition. Table 5. ■Results of experimental fumigations of string bepjis at San Juan, P. R., 1939 Treatment Storage Date Dosage, Duration, Vacuum , Temp. , Results pounds minutes inches otp Feb. 17 3 90 15 77 room refrig. No injury. •Do. U 90 15 77 room refrig. Do. Injury. Feb. 21 2 90 15 71 • ship* No injury. Mar. 2 2 90 15 79 refrig. Slight injury 3 90 15 79 refrig. Moderate injury k 90 15 79 refrig. Severe injury Mar. 8 2 90 15 77 ship* refrig. No injury. Very slight injury. Shipped to New York City -J - Pigeon peas .— In San Juan one test was also made with freshly picked pigeon peas, in which one crate was fumigated on February 23 and shipped to New York with numerous untreated packages. A dosage of 2 lb. for 90 Bin. in a I9 11 vac. was used. There was little difference between the fumigated crate and the others when they were examined upon arrival at New York. Commercial Application Following the first trial fumigation of 2lk one-bushel hampers of green lima beans on December 6, 1938 t all infested shipments (a lot under one customs entry was considered a shipment) were allowed entry following fumigation and reinspection. This method was followed on weekly impor- tations until January 25 t 1939» after which the reinspection was eliminated since it had become apparent that the treatment was dependable. Tho shipping season, previously terminated on April 1, was extended for several weeks with the provision that all incoming pod vegetables be fumigated. Up to April 1, 1939. 7.765 hampers of green lima beans were fumigated, and from April 5 to 19, ^-.73° more were treated, a total of 12,501- During April 97 crates of pigeon peas were also fumigated in New York. The trade was well satisfied with the quality of both these products following fumigation. When the next shipping season opened on November 1, 1939i * ns Bureau required the fumigation of all entries of green pod vegetables with a dosage of 3 Id. for 90 min. in a 15" vac. at prevailing temperatures. The shipments of lima beans from Cuba were fumigated at New York upon arrival during November, but it was soon realized that this would be un- satisfactory because of (l) cost, (2) overcrowding of existing facilities, and (3) delay in delivery for at least 2 days ' f ter docking. As a result, a fumigation plant was built at Havan?, Cuba, with the intention of treating all beans before shipment. The Division of Control Investiga- tions provided plans for the plant, and the writer tested the equipment when finished. The plant was built by the Cuban American Terminal Company for the Asociacion de Cosecheros y Exportadores de Frutas y Vegetales de Cuba, and all fumigations were to be certified by the Seccion de Sanidad Vegetal de la S^cretaria de Agricultura. It consisted of two atmospheric fumiga- tion vaults of 2,500 cubic feet capacity, each capable of holding 93& hampers, "h.1 ■2'Fven though experiments in Puerto Rico had shown that atmospheric fumigation was as efficient as vacuum for the destruction of pod borer larvae, the use of the latter method w^s continued in New York, since equipment was available and the commercial procedure had already been established. However, for the purpose intended, atmospheric fumigation w^s preferred for use in Havana owing to the mueh lower cost of equipment. Based on the data obtained at San Juan, a dosage rate of I.5 lb. for 2 hr. at prevailing temperatures was recommended for treatments at Havana, which was calculated to "be sufficiently in excess of the neces- sary minimum to care for variations in temperatures or other factors, and well within the range of host tolerancr. Under routine operation these vaults provided information on (l) prevention of sweating and (2) length of aeration period following fumigation. It had been foreseen that sweating would "be a problem owing to the confining of large quantities of freshly picked ■he ans in an airtight vault. However, it, was soon determined that heating was prevented if the circulat- ing blower was operating from the time loading started, although sweating proceeded until the atmosphere w*s near or at- saturation. Frequent observations of partial and full loads in the vaults showed that temperatures equalized to the prevailing ^ir temperature regardless of whether the hampers were above or below that point when loaded into the vaults. It had been anticipated that the aeration period would, take several hours, and this problem was considered a serious obstacle in perfecting a satisfactory commercial routine. However, actual working tests proved that a much shorter time was satisfactory. At the end of each fumigation an exhaust vent was opened, the door of which dropped in front of the blower used for circulation, thus directing all of its discharge to the outside of the vault. At the- same time two intake vents at the opposite end of the vault were opened to admit fresh air to replace th air-gas mixture, which was being ejected. The blower in each vault had a capacity of 1,100 cubic feet per minute. Tests wre made with a halide leak detector of partial and full loads., and the rapidity of aeration was determined in this manner. Und-r prevailing temperature conditions (70° -and above) it was determined that loads of 3^0 to 500 hampi rs were cleared of all detectable concentra- tions of gas in 2 hours, and loads of 600 to 900 in 3 hours. The free air in the vaults cleared in U5 minutes or less, so it was s*fo for the operator or workmen to enter, since the definite draft toward th: exhaust vent carried away gas still disseminating from the. fumigated hampers. Tight hampers (with no cracks between staves) often held a det^ctabl<~ quantity of gas for periods longer than indicated above, but dissemination from these occasional containers was such that the dilution with air surrounding them was sufficient to lower the concentration to undetectable amounts. Other test loads w^rc removed from the vaults before the hampers were free of gas but after the air surrounding showed no detectable cone Ti- trations. In normal handling about 1 hour elapsed bctweon unloading and transfer to a precoolcr, and in all cases this period was sufficient to free all hampers of gas before entering refrigeration. In still other tests hampers still showing detectable amounts of gas were put in a pre- cooler where cold air was forced through at a rapid rate. The moving air carried away diffusing gas so rapidly that it was not detectable outside the hampers. In the tests made at Havana, as well as in those previously made in New York, it was found that even though hampers contained gas concentra- tions as high as 100 to 150 parts per million, when they were placed in an exposed position, the gas removal was of a rate that allowed for very great dilution so that traces could "be found only within a few inches of the package. This applied to large quantities of material as well as snail. The observations indicated, however, that quantities of fumigated material should not be confined in closed quarters unless adequate ventilation is assured. During the winter of 1939-1+0 the following quantities of imported green pod vegetables were fumigated either at New York or Havana, as indicated: Green lima beans - - 14,770 hampers of Cuban origin at New York 118 hampers of Puerto Rican origin at New York 77.293 hampers of Cuban origin at Havana Pigeon pens- - - - - 5»57S boxes of Puerto Rican origin at New York String beans - - - - 31 . 667 hampers of Cuban origin at Havana 1,1+71 boxes of Puerto Rican origin at New York All the produce fumigated at New York was given a dosage of } lb, foi 90 min. in a 15" vac. at temperatures. mostly between k0° and 50°. All produce fumigated at Havana was given a dosage of 1.5 lb. for. 2 hr. at atmospheric pressure at prevailing temperatures (70° to 90 ).-' The large quantity of string beans imported was due to a high market following freezing weather in bean-growing areas of the southern states early in I9U0. • • All three of these products were kept under constant observation, and no injury or other lessening of quality was found. The writer tested many samples for taste and found no difference from untreated samples. The trade accepted these vegetables, and there have been no complaints of injury from them. i/ See footnote 3» - 10 - CIFOLLINI HUBS Problem Dormant "bulbs of Muscari comosum , known in the trade "by the name cipollini (meaning "little onion" in Italian), have been imported in quantity from iiorocco for consumption as food. Thf.se bulbs wore not cultivated, but were collected from mountainsides where they grow wild in great numbers. They were often infested with larvae of E:co s oma lusitanica , a chrysomelid beetle not known to occur in the United States. Infestation was generally very light in bulbs imported during the early winter months, as they had been in storage for some time and evidently the larvae present had left to pupate. Soon after the beginning of a new year, however, so-called new-crop bulbs which had recently been dug began to arrive. These were usually moderately infested. 2/ Until 1932 all infested shipments had been admitted only after a prescribed hot-weter treatment of 3 hours at llU c F. Since practically all importations were made during the winter months, this treatment was unpopular for reasons of (l) extreme difficulty of drying quantities of bulbs under winter conditions in unheatcd warehouses, (2) cost due to excessive handling necessary in drying, and (3) high loss of bulbs in storage when cold weather prevented proper drying. The hot-water treat- ment was efficient as far as control of insect larvae was concerned, but owing to the reluctance of importers to use this method and the losses following its use, the Division of Foreign Plant Quarantines desired a less costly and more satisfactory treatment. Insect-Mortality Studies On November 25 , 1933, the first tests were made with a few infested bulbs removed from an importation of cipollini. Four of seven larvae survived a fumigation with 2 lb. for 90 min. in a 15 " vac. at 70°, p nd h of 5 larvae showed activity after k days following a fumigation with the dosage raised to 2.5 lb. Larvae of the narcissus bulb fly ( Merodon equc stris ) present in the bulbs also survived these dosages. Be'caUse of the scarcity of available larvae of Exosoma lusitanica , no further tests could be made at that time, so a dosage rate of U lb. for 2 hr. in a 15" vac. at 65 ° or above was arbitrarily selected for use in a test fumigation of 700 cases (?o to 30 tons). These bulbs were' supplied by an importer desirous of using methods other than hot-water treatment, and were- treated on December 5. The bulbs were warmed to ^■'Kisliuk, M. Some Scientific Contributions Made at the Port of New York. Jour. Boon. Ent. 33 (2): 376, 19H0. - 11 - ^proximately 75° before fumigation. Twenty-seven larvae of E. lusitanica and 17 of M-rodon equestris were recovered fror.i cases selected at random from the load, and all were dead within k% hours, with bodies collapsed and partially or wholly discolored. Only incidental recoveries of occasional dead larvae were made from many additional commercial fumigations' at the above dosage rate until January 11, 19^0, when a number of larvae were recovered from beneath stacked cases of fumigated bulbs. Those larvae were active when collected but all died within a few days. A later recovery of over 30 larvae in a similar manner also resulted in complete mortality. On January 13, 19^0> about 10 active larvae were fumigated with k lb. for k hr. in a 15 " vac. at U6-5O . All were killed. Host-Tolerance Studies At New York City small lots of imported cipollini bulbs were subjected to a series of fumigations v/ith methyl bromide in November 1938. About HOO bulbs were used in each sample, as listed in table 6. These bulbs were kopt under observation for 30 days or longer and showed no evidence of injury from treatment. Twenty-four bulbs from each of the first four treatments given in table 6 were planted in the laboratory greenhouse and forced during January and February. All lots grew and flowered normally. It was assumed from these tests that the bulbs were very tolerant to methyl bronide fumigation, and it was on this assumption that a treatment of U lb. for 2 hr, in a 15" vac. at 65 ° or above was selected for commercial use. Table 6. — Results of experimental fumigations of cipollini bulbs at New York City, 1938 Treatment Re Date Dosage, Duration, Vacuum , Temp. , suits poi' ads minutes inches °F. Nov. 25 2 90 15 70 No injury 2.5 90 15 70 Do. 3 90 13 70 Do. U 90 15 70 Do. 2.5 120 none 70 Do. Nov. 30 3 90 15 ^3 Do. k 90 13 ^3 Do. 5 90 15 U3 Do. k 90 25 U3 Do. - 12 - In November 1339 further experimental tests of bulb tolerance were at Washington, D. C, in - n attempt to establish the maximum dosages that : uld be used safely. Ih- experiments tested increases of dosage, _ r. , and vacuum. The results of these tests arc giver, in table 7. Fable 7- — Results of experimental fumigations of cipollini bulbs at tingt n, D. C. , November 2^ and 25, 1933 Treatment Decay* id. "eulbs Number Add itional foun 3 number c Remarks ■ Dorat ion, Vacuum , Temp. , - on ? e hours inches CT after 27 iays after kl days U k 15 70 o • 5 2 15 70 1 1 6 2 15 70 z 2 15 70 H/3U* U/23* U/lO buds dead 5 k 15 ±5-50 2 6 k 15 50-55 2 6/10 buds dead k 2 15 90 k 2 25 70 6 /Us k 3 25 70 3/70 k k 25 70 21 /h6 3/25 U/22 buds iiead - - - -Jireo number denotes cumber of decayed bulbs out of total given by sec r. : . cumber, i.e., 11/3*+ = H decayed bulbs out of a total of }K, In the examination of the bulbs used ir. this series, all decayed removed at the time, so that the number of decayed bulbs after hi -".ays in stox re ir. addition to the number after 27 3.ays. It was observei that the checks and nany of the treated bulbs showed considerable :r.t of new buds in the neck region. In the severest treatments s r of these buds h- . tilled end discolored, and the remainder were still inactive. In direct association with this factor was a signif- icant loss of bulbs from internal decay. Therefore, where both conditions occurred it was judged that treatment was responsible for injury.—' Where .of bulbs w*e - -t the remainder had well-developed new buds, >cay was considered as originating fron external bruises or cuts. — In subsequent studies with new-crop bulbs it "^e carte evident that ' ud could not be used as a criterion of fumigation effect _se of tb ely small size of the bud, sir.ce it was only in the formative state. - 13 - On this basis, then, two treatments were considered to have caused definite injury, namely, S lb. for 2 hr. in a 15" vac. at 70 c , and U lb. for k hr. in a 25" vac. at 70°, while s third, 6 IV. for k hr. in a 15" vac. at 50~55°» w;is on the borderline in that buda were killed but no loss of bulbs followed. The. remaining dosages were apparently all within the tolerance range of cipollini bulbs. This suggested a very safe margin between the recommended treatment and the maximum tolerance of the bulbs. It nust be pointed out that the above tests were made with "old- crop" bulbs, dug during the spring ->nd siEnor and w-11 cured before shipping. These bulbs w~re probably in their natural dormant period at this time, as evidenced by the. presence of new flower v u^.s in the bulbs. N?w-crop bulbs, which were apparently dug during the growing season; are in an abnormal condition and night exhibit a different degree of tolerance to fumigation treatments. Under routine commercial conditions, as will ^e shown in the following section, there was less loss from new-crop % ul v s than from old-crop fumigated with the recommended losage. Commercial Application Various importers of cipollini bulbs were anxious for an alternative treatment to the recommended hot-water immersion, so after the first series of experimental tolerance tests in November 1938 p iot of 700 cases was offered by an importer for an experimental large-scale treatment. As noted previously, a dosage rate of U l v . for 2 hr. in a 15 " vac. at 65° or above was selected for trial. The bulbs were raised from p. storage temper- ature of approximately ^5° to 7o° by placing the entire lot in the fumigating vault end applying heat through the medium of a steam coil in the bottom. This vault was a long cylinder of the type frequently used for vacuum fumigation. There was no circulation other than convection currents, and the temperature at the extreme top reached about 110°. The end doors were kept open to prevent sweating. In this instance the bulbs remained in this warm location for 3 days over a weekend. Following fumigation, the bulbs were reexamined, and when all larvae were found dead the shipment was released from quarantine. Samples of bulbs saved from cases selected at random from this fumigation were kept under observation for several weeks and showed no apparent effect from the treatment. As soon "s the trade was satisfied that no injury occurred, all subsequent infested importations were fumigated rather than treated in hot water. In the fiscal year 1933-39, 9.925 c^ses were fumigated. - lU - During 193^, 1939. and January l^O the recommended treatment required a bulb temperature of 05° or above. Practically all shipments, with the exception of tv/o or three fumigated, in the late soring of 1939, were heated as described atove to meet this requirement. In most instances, if a shipment of bulbs was placed in the vault late in the afternoon, it would br warmed to 63 ° the following morning without the air temperature at the top of the vault going above 110°. This procedure was considered a benefit by most importers because of the drying of moist or moldy bulbs. On January 2U, 13^0, the reconm ended treatment was broadened to allow fumigation at storage temperatures as follows: k lb. for 2 hr. in a ly n vac. at temperatures above 63 °, or k lb. for U hr. in a 15" vac. at temperatures below 65 . In the fall of 1939 certain importers suggested that fumigated bulbs did not store so well as untreated cries, although apparently there was no effect on quality. Therefore en intensive study of all shipments fumigated during the winter of 1939-^0 was undertaken. Samples of treated and untreated bulbs were saved from each commercial fumigation and kept under observation at Washington, D. C, and, whenever possible, observa- tions were made of lots in storage in New York City. From November 1, 1339. until May 1, 19^+0, samples from 3^ fumigated lots, representing 13,111 cases of bulbs, were kept under observation for approximately 1 month following fumigation. Each sample weighed about k pounds and contained from UO to 63 or more bulbs, depending on their size. Nine of the 3*+ samples showed considerable loss during storage (see table 8), the remaining 25 samples keeping in excellent condition. Where, two or three bulbs in a sample decayed, it was attributed to normal storage loss, since a similar loss occurred in some untreated samples. Of the 9 samples showing a high percentage of loss in storage, 1 was found to have much higher loss in the sample than in a part of the original ship- ment still in storage, and 2 more were from shipments frozen before treatment. Three of the remaining 6 lots belonged to one importer who received much cipollini from miscellaneous sources, and none of it was selected or gra.ded. - 15 - Table 8. — Results of storage tests with Bamples from shipments of cipollini bulbs fumigated, 1933-^0 Number of Number of decayed Date cases bulbs in 3?.mples Remarks fumigated Untreated Fumigate d 1939 Nov. 25 Nov. 25 1 , Uoo 2/43* Nov. 27 15 As Nov. 27 850 3/50 3/52 Nov. 29 100 7/48 1/U5 Nov. 29 200 14/53 Dec. 1 520 65 /so 60 ( :ases in sto rage shoi only to 10$ decay. Dec. 1 200 1/47 22/63 Dec. 4 150 2/5^ Dec. 12 566 Dec. 13 500 19^0 Jan. 5 300 1/51 10/45 Jan. 9 2,100 1/54 Jan. 10 100 Jan. 13 100 29/U0 Jan. 22 400 Jan. 26 132 MS/49 Lot frozen on dock. Feb. 7 44 3 40/49 47/47 Do. Feb. 9 150 New- wet -crop bulbs, and moldy. arrived Feb. 9 300 Do. Feb. 15 150 • Do. Feb. 16 50 Do. Feb. 20 150 Do. Feb. 20 200 Do. Feb. 27 200 35 M Do. Mar. 8 Uoo Mar. 19 200 Mar. 19 200 Mar. 19 200 Do-. Mgr. 22 100 Mar. 22 698** ■ Do. Mar. 23 65O** Apr. 18 ■ Apr. 24 1, 302** * First figure denotes numb ■•r of decayed bulbs 3Ut of total givpn by secon d figure. ♦♦Treated without heating with 4 lb. for 4 hr. at 4s c , 45 ° , 56°, and 58 , respectively. - 16 - A part of the stock treated on December 1 (52O cases), which showed a loss of 65 out of SO "bulbs In the sample, was located in storage and examined January 10. Sixty cases remained, stacked 5 high and 12 long in a single row. One stack wns removed from near the center, and samples were taken from each case. The percentage of decayed bulbs varied from to over 10 in the 5 cases. New buds in a number of bulbs cut open v/ere in normal condition. Either the sample kept for observation had been selected from a case having a large amount of incipient decay, or else its storage conditions were unfavorable. The results of the examina- tion were : Top case — 2 of 200 bulbs from two locations in case decayed (l;£) Second case — 5 °f 200 bulbs from one end of case decayed Third case — 12 of 112 bulbs from one end of case decayed (1Q.7$) Fourth cp.se — 2 of 200 bulbs from one end of case decayed (l#) Bottom case — of 200 bulbs from two locations in case decayed (0$) In one shipment which had been frozen before treatment the loss was attributed definitely to that fact, since both treated and untreated samples decayed. In the other instance of bulbs frozen prior to treatment there was almost total loss in the treated sample but none in the check. This may have been due to the effect of heating the frozen b\ilbs. The samples from shipments fumigated during November and December v/ere selected at random before and after fumigation, whereas samples, from those treated after January 1 were taken from the same case in each instance. The former method may have contributed to a chance selection of a sample from a case with high incipient infection. It was indicated that old-stock bulbs may have been more susceptible to storage losses, since S of the 9 samples showing loss were from that type. Therefore, with unexplained high storage losses in only 6 of ]>k tests, it w?s assumed that fumigation with the recommended dosages did not cause injury to the bulbs or foster conditions contributing to storage decay • CHESTNUTS Problem Imported chestnuts often have been infested with larvae of weevils ( Curculio sp., formerly Balaninus ) a$d with larvae of the European eodling moth ( Laspeyresia splendana ) , necessitating a disinfestation treatment. For sevpral years infested nuts had been treated in hot water of 112° F. for U5 minutes. This treatment was expensive because of the excessive handling necessary when quantities of nuts were treated, and it offered the - 17 - same difficulties of drying during winter months as were encountered in hot-water treatment of cipollini "bulbs. A l?ss expensive and more rapid treatment , such as fumigation would provide, wqs desired for use on the Pacific coast for importations of Japanese chestnuts as well as in New York for an anticipated increase of shipments from Mediterranean countries. Insect-Mortality Studies No live specimens of either species of insects likely to be in imported chestnuts were available for use in experimental tests, so studies were made with larvae of the native chestnut weevils Curculio proboscideus and C. a uriger . The following recommendation for treatment of imported chestnuts was based on these experiments: Above 70°- — k lb. for 2 hr. in a high sustained vacuum (25" or more) Between 50° and 70° — k lb. for k hr. in a high sustained vacuum Below 50 ° — ^ lh. for 5 hr. in a high sustained vacuum In chestnuts examined following treatments of commercial shipments fumigated with the above schedule it w-, 3*5. and U lb., all for 90 nin. in a 15" vac. at approximately 70°. The chestnuts were examined by C. A. Reed, of Nut Investigations, Bureau of Plant Industry, and no change in taste or quality could be detected. On December 15, further tests were made with Italian chestnuts ( Castanea sativa ) . Dosages of 3> ^» and 5 1^« > all f° r ?■ hr. in a 15" vac. at 75°. and 3 lb. for 2 hr. in a 25" vac. at 75° were used. These chest- nuts were also examined by Mr. Reed, and no effect to taste or quality could be detected. During 1939 more extensive tests were made at Washington with American-grown chestnuts of Castanea mollissima (Chinese) , C. crenata (Japanese), and various hybrids of each. Early- and late-maturing strains of each were tested, as well as immature (nuts just dropped) and mature (nuts held about 2 weeks until sweet) samples of e?ch. In all, 31 samples were treated. Dosages up to the following limits were tested: k lb. for 3 hr. in a 15" vac. at 70° 7 lb. for 90 min. in a 15 " vac. at 70° 6 lb. for 2 hr. in a 27" vac. at 70° k lb. for 3 hr. in a 27" vac. at 6o° 5 lb. for 3 hr. at atmospheric pressure at 70° - IS - All the samples were examined "by Mr. P.eed for taste and quality, and no change could be detected. Commercial Application Importers of chestnuts showed no reluctance in accepting methyl bromide f\imigation in lieu of hot-water treatment. Starting with a ship- ment of 113 kegs on November 1, 1939» 8,31b containers (baskets, boxes, and kegs), mostly of Portugese origin, were fumigated during November, December, and January, at New York City, and 9U0 containers of Japanese chestnuts at Seattle, Wash. Some of the shipments of chestnuts were heated before fiimigation in order to take advantage of the shorter exposure pr-riod, and others were fumigated at storage temperatures between U0° and 6o°. Samples saved from 13 fumigated shipments were kept under observa- tion at Washington, D. C. In no instance was there any increase in loss during storage, nor was there any effect on taste or quality. Two shipments consisting of several hundred baskets, which had been fumigated on December 22, wore examined in storage on January 10 and were in almost the same condition as at the time of arrival. CHILEAN PEACHES Problem A shipment of Elberta peaches from Chile was found infested with live adults of Pantomorus sp., a close relative of the white-fringed beetle. An emergency treatment was needed for this shipment. Commt rcial Application Because peaches had been successfully fumigated with methyl bromide in previous tests, the importer offered the shipment for experimental treatment without preliminary trials in this instance. , The entire lot of 606 boxes was fumigated with 3 lb. for 30 nin. in 9 15" vac. at 38-Uo c on February 17, 19^0. The fruit was green. The adults of the white-fringed beetle arc known to be killed at normal temperatures with very low dosages of methyl bromide, therefore for this closely related species the selected rate was considered to be well in excess of the amount needed after the effect of a low temperature and the use of vacuum had been calculated. Samples of untreated and fumigated peaches were retained and observed for several days to study any effect that .might result from fumigation. Both samples ripened normally and showd no offset on either taste or ouality. Later reports were that the peaches moved through commercial channels without any r-port of injury. - 19 - ARGENTINE GRAPES . Problem A shipment of five varieties of grapes arriving in Naw York from Argentina were found infested with live adults of Pant ononis sp. An emergency treatment was needed for this shipment. Host-Tolerance Studies The infested shipment was allowed to move from the piers to a "bonded .cold-storage plant. On March 7 several boxes of grapes of the varieties Thompson Seedless, Pizzutello, Black Olivet, and Ribier, all of the so-called soft type, were removed and subjected to experimental fumigations at the storage plant. The following tests were made, all at atmospheric pressure: 3 lb. for 2 hr. at 3O k lb. for 2 hr. at 5O 5 lb. for 2 hr. at 3O Each sample was divided, one half going back into storage at 3^°> the .other half being placed in an open storeroom »„t 60-70°. On March 11 all samples were observed by a committee of grape importers and experts, who could not distinguish between untreated and fumigated samples in either those kept at room temperature or those kept in storage. Commercial Application On March 12, 2,^32 boxes of grapes were removed from storage and fumigated with a dosage of ]> Vo. for 2 hr. at atnospheric pressure at 50°. (The duration was extended to 2 hr. to compensate for the increase in pressure to normal atmospheric instead of partial vacuum as used in the treatment of peaches.) The grape temperature rose from 3^° to approxi- mately 5O during transit to the fumigating plant. The treatment was performed in a vacuum vault but no vacuum was used at any point in the procedure. The grapes were removed from the plant after a sufficient airing period and taken directly to a fruit auction, where they were sold. Later reports were that no bad effects resulted from the fumigation, but that the quality was somewhat lowered by the changes in temperatures and subsequent condensation of moisture on the fruit. SUMMARY Several types of imported perishable food products have been successfully fumigated with methyl bromide during the past 2 years to free them of certain insect pests. Data of experiments for destruction of these insects, tolerance of hosts, and commercial application are given. UNIVERSITY OF FLORIDA IlllllllWlllllWlliWlllllllll 20 . 3 1262 09224 7492 In tests made in Puerto Rico, larvae of Manic a testulalis woro all killed by dosages of 0.5 lb. of methyl bromide per 1,000 cubic feet of space under cither vacuum fumigation conditions for 90 minutes or atmospheric conditions for 2 hours. Green lima beans were found to be uninjured by dosages as high as 5 pounds at 70° or above. String beans and pigeon peas tolerated dosages of 2 pounds. Fumigation of green pod vegetables was applied commercially under high- temperature conditions in Havana, Cuba, and under low-temperature conditions at New York City, with dosage rates of 1.5 lb. for 2 hours at atmospheric pressure, and 3 lb. for 90 min. in a 15" vac, respectively. In 1933-39. 12,501 hampers of green lima beans and 97 boxes of pigeon peas were fumigated, and in 1939-^0. 92,181 hampers of lima beans, 5»578 boxes of pigeon peas, and 33»13S hampers of string beans. Larvae of Sxosona lusitanica infesting cipollini bulbs were found to be killed by a dosage of k lb. per 1,000 cubic feet for 2 hours above 65 ° or for h hours below 65 °. Cipollini bulbs proved to be very tolerant to methyl bromide fumigation. Fumigation of cipollini bulbs w~s applied commercially, and in routine fumigations 9»9^5 cases were treated in 1938-39 and 23,670 cases in 1939-UO. Chestnuts were also found (in experimental tests) to be very tolerant of methyl bromide fumigation as far as taste and quality were concerned. In the commercial application of this fumigation, 9,256 packages of chestnuts were fumigated in 1939-^0. One commercial fumigation each of Chilean peaches and Argentine grapes was performed without injury to the fruits.