LIBRARY 
 STATE  PLANT  BOARD 
 
 February  1950  E-794 
 
 United  States  Department  of  Agriculture 
 Agricultural  Research  Administration 
 Bureau  of  Entomology  and  Plant  Quarantine 
 
 TESTS  WITH  ACR  YLONITRILE  -  CARBON  TETRACHLORIDE 
 AND  HYDROGEN  CYANIDE  AS  FUMIGANTS  FOR 
 INSECTS  IN  CIGARETTE  TOBACCOS 
 
 By  C.  O.  Bare  and  Joseph  N.  Tenhet 
 Division  of  Truck  Crop  and  Garden  Insect  Investigations 
 
 Flue-cured  and  Turkish  tobaccos  are  attacked  in  storage  by  two  in- 
 sect pests,  the  cigarette  beetle  (Lasioderma  serricorne  F.)  and  the 
 tobacco  moth  (Ephestia  elutella  Hbn.).   A  new  commercial  fumigant  has 
 been  developed  which  is  composed  of  acrylonitrile  and  carbon  tetrachloride 
 (50-50  by  volume).   With  material  supplied  by  the  manufacturers  and  in 
 cooperation  with  several  tobacco  companies,  tests  have  been  made  to 
 compare  this  fumigant  with  hydrogen  cyanide. 
 
 Atmospheric  Fumigation 
 
 Laboratory  tests. --Replicated  laboratory  tests  were  made  in  33-cubic- 
 foot  chambers,  at  atmospheric  pressure  and  70°-82°  F.,  and  the  exposure 
 period  was  72  hours.    The  toxicity  of  acrylonitrile -carbon  tetrachloride 
 to  large  unprotected  larvae  of  the  cigarette  beetle  and  the  tobacco  moth 
 was  roughly  comparable  to  that  of  hydrogen  cyanide.   Against  large 
 larvae  of  the  tobacco  moth  hydrogen  cyanide  was  the  more  effective  at 
 very  low  dosages.   At  2  or  3  ounces  per  1,000  cubic  feet  the  new  fumigant 
 seemed  to  be  slightly  more  effective;  but  4  ounces  of  hydrogen  cyanide 
 killed  all  moth  larvae,  whereas  6  ounces  of  acrylonitrile- carbon  tetra- 
 chloride was  required  for  a  complete  kill  (table  1).  It  will  be  noted  that 
 3|  to  4  ounces  per  1,000  cubic  feet  of  the  new  fumigant  killed  all  unpro- 
 tected cigarette  beetle  larvae. 
 
 In  other  replicated  laboratory  tests  at  summer  temperatures  (70°- 
 95°  F.)  approximately  28  ounces  of  acrylonitrile- carbon  tetrachloride 
 per  1,000  cubic  feet  with  a  48-hour  exposure  or  32  ounces  with  a 
 24-hour  exposure  killed  all  cigarette  beetle  larvae  to  a  depth  of  9 
 inches  in  bales  of  Turkish  tobacco  (table  2). 
 
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-  4  - 
 
 Tests  in  commercial  chambers .-- Tests  were  conducted  in  5,000- 
 cubic-foot  atmospheric  chambers  to  determine  the  effectiveness  of  this 
 fumigant  under  semicommercial  conditions.   As  would  be  expected,  it 
 was  found  that  the  gas  did  not  penetrate  hogsheads  of  flue- cured  tobacco 
 sc  readily  as  it  did  the  less  dense  bales  of  Turkish  tobacco.    These  tests 
 were  made  at  temperatures  of  70°-85°  F.   A  16-inch  oscillating  electric 
 fan  was  operated  in  the  chamber  for  1  to  2  hours  at  the  beginning  of 
 each  test  to  prevent  stratification  of  the  gas.  A  72-hour  exposure  gave 
 better  penetration  of  hogsheads  of  tobacco  than  a  48-hour  exposure.  With 
 a  72-hour  exposure  a  dosage  of  20  ounces  per  1,000  cubic  feet  gave  com- 
 plete kill  of  cigarette  beetle  larvae  to  a  depth  of  9  inches  in  bales  of 
 Turkish  tobacco.   However,  at  no  dosage  or  exposure  was  complete  kill 
 obtained  to  such  depths  in  hogsheads  of  flue-cured  tobacco.   A  dosage  of 
 32  ounces  per  1,000  cubic  feet  with  a  72-hour  exposure  gave  a  mortality 
 of  cigarette  beetle  larvae  of  72  percent  at  9  inches  in  hogsheads  of 
 tobacco,  as  compared  with  36  percent  at  the  same  dosage  of  gas  but  with 
 a  48-hour  exposure. 
 
 Tests  in  warehouses .- -In  1947  and  1948  three  large  warehouses  of 
 flue-cured  tobacco  in  hogsheads  were  fumigated  with  acrylonitrile-carbon 
 tetrachloride.    Two  of  them  had  a  capacity  of  280,000  cubic  feet,  and  one 
 of  600,000  cubic  feet.   In  all  fumigations  the  exposure  period  was  72  hours 
 and  the  temperature  range  was  65°- 90°  F.   Electric  fans  were  operated 
 for  the  first  4  to  5  hours  to  prevent  stratification  of  the  gas.    By  means 
 of  an  air  compressor  the  gas  was  introduced  into  the  buildings  through 
 copper  tubing  permanently  installed  for  fumigation.    The  acrylonitrile- 
 carbon  tetrachloride  mixture  was  in  high  pressure  cylinders  of  the  type 
 used  for  hydrogen  cyanide,  and  was  under  carbon  dioxide  pressure. 
 However,  air  pressure  was  required  to  force  the  furnigant  into  the 
 building.    The  mortality  of  test  insects  used  in  these  experiments  is 
 shown  in  table  3. 
 
 In  the  first  warehouse  the  dosage  was  inadequate,  and  in  this  and 
 in  the  second  warehouse  some  unknown  factor  reduced  the  effectiveness 
 of  the  fumigant.    Perhaps  the  sheet-metal  buildings  were  not  so  tight  as 
 they  were  thought  to  be,  or  possibly  the  cinder  floors  were  more 
 absorptive  than  was  anticipated  for  a  gas  heavier  than  air.  Nevertheless, 
 the  penetration  of  the  gas  in  these  tests  was  superior  to  that  obtained 
 with  hydrogen  cyanide,  in  previous  tests  under  similar  conditions.  In 
 the  third  warehouse,  a  brick  building  with  concrete  floors,  the  penetration 
 of  the  gas  and  the  mortality  of  test  insects  at  depths  of  5  to  9  inches, 
 above  90  percent  at  a  9-inch  depth,  were  the  best  ever  observed  in 
 warehouse  fumigation  of  flue-cured  tobacco  in  hogsheads. 
 
 The  effectiveness  of  fumigation  in  the  third  warehouse  is  further 
 confirmed  by  the  weekly  catches  in  suction  light  traps.    Little  build-up 
 of  insect  population  was  noted  3  months  after  fumigation  with  acryloni- 
 trile-carbon tetrachloride.    In  contrast,  the  average  catch  per  trap 
 
-  5  - 
 
 from  six  other  comparable  warehouses  fumigated  at  about  the  same 
 time  with  16  ounces  of  hydrogen  cyanide  per  1,000  cubic  feet  showed  a 
 much  greater  increase  in  tobacco  moth  population  late  in  the  summer. 
 Unfortunately  for  the  experiment,  the  initial  cigarette  beetle  population 
 in  the  warehouses  fumigated  with  hydrogen  cyanide  was  not  appreciable. 
 The  insect  populations  of  these  warehouses  are  shown  in  table  4. 
 
 Vacuum  Fumigation 
 
 Laboratory  tests.--Tests  were  made  at  reduced  pressure  to  determine 
 the  minimum  dosage  of  acrylonitrile- carbon  tetrachloride  that  would  kill 
 all  cigarette  beetle  larvae  in  bales  of  Turkish  tobacco.    These  tests  were 
 conducted  in  a  33- cubic-foot  steel  chamber  in  which  the  air  was  exhausted 
 to  a  pressure  of  28  to  29.6  inches  of  mercury.    The  exposure  period  was 
 3  hours,  and  temperatures  ranged  from  70°  to  86°  F.    By  means  of  the 
 customary  steel  test  spikes  (2),  large  larvae  of  the  cigarette  beetle  were 
 placed  in  bales  of  Turkish  tobacco  (approximately  140  pounds  each)  at 
 depths  of  1,  3,  5,  7,  and  9  inches.    Dosages  tested  were  from  8  to  32 
 ounces  per  1,000  cubic  feet.   All  tests  were  replicated  five  times. 
 
 Table  5  shows  that  under  the  conditions  of  these  tests  the  minimum 
 dosage  which  could  be  depended  upon  to  produce  100  percent  mortality 
 was  20  ounces  per  1,000  cubic  feet. 
 
 Tests  in  commercial  chambers.- -A  series  of  tests  in  commercial 
 vacuum  fumigation  chambers  of  1,082  cubic  feet  each  was  conducted  in 
 the  fall  of  1946.    Bales  of  Turkish  tobacco  and  hogsheads  of  flue-cured 
 tobacco  were  fumigated  in  vacuum  under  commercial  conditions.  The 
 chambers  were  evacuated  to  a  pressure  of  28.5  to  29  inches  of  mercury. 
 The  exposure  period  was  4  hours  and  the  temperatures  were  below  70°  F. 
 As  shown  in  table  5,  a  dosage  of  48  ounces  of  acrylonitrile- carbon  tetra- 
 chloride per  1,000  cubic  feet  killed  all  cigarette  beetle  larvae  to  a  depth 
 of  9  inches  in  bales  of  Turkish  tobacco.   However,  a  dosage  of  64  ounces 
 per  1,000  cubic  feet  was  necessary  to  kill  all  larvae  to  the  same  depth  in 
 hogsheads  of  flue-cured  tobacco. 
 
 In  another  series  of  tests  in  the  same  vacuum  chambers  in  1947, 
 acrylonitrile- carbon  tetrachloride  was  approximately  equivalent  to 
 hydrogen  cyanide  in  effectiveness.   At  tobacco  temperatures  of  42°-57°  F. 
 and  air  temperatures  of  31°-64°,  a  dosage  of  2\  pounds  of  acrylonitrile- 
 carbon  tetrachloride,  with  an  exposure  of  4  hours,  killed  all  cigarette 
 beetle  larvae  to  a  depth  of  9  inches  in  bales  of  Turkish  tobacco.  However, 
 in  a  third  series  of  tests  under  similar  conditions,  except  at  somewhat 
 lower  tobacco  temperatures  (29°-57°),  an  occasional  larva  survived 
 dosages  up  to  4  pounds  of  acrylonitrile- carbon  tetrachloride  per  1,000 
 cubic  feet. 
 
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-  7  - 
 
 Table  4. --Average  numbers  of  tobacco  moths  and  cigarette  beetles 
 caught  per  suction  light  trap  in  a  warehouse  fumigated  with 
 acrylonitrile-carbon  tetrachloride  and  in  six  warehouses 
 fumigated  with  hydrogen  cyanide.    Wilson,  N.  C,  and 
 Portsmouth,  Va.,  1948 
 
 Tobacco  moths 
 
 Cigarette  beetles 
 
 Week 
 ending 
 
 Acrylonitrile- 
 carbon  tetra- 
 chloride 
 
 Hydrogen 
 cyanide 
 
 Acrylonitrile- 
 carbon  tetra- 
 chloride 
 
 Hydrogen 
 cyanide 
 
 May 
 
 18 
 
 26 
 
 176 
 515 
 
 95 
 151 
 
 40 
 76 
 
 0 
 0 
 
 Ti  i  n  r* 
 %J  Ullfc; 
 
 i 
 i 
 
 8 
 
 15 
 
 22 
 
 29 
 
 619 
 355 
 Fumigated 
 
 301/ 
 -J/ 
 
 135 
 184 
 143 
 Fumigated 
 2 
 
 108 
 
 93 
 
 Fumigated 
 .11 
 
 0 
 0 
 0 
 
 Fumigated 
 0 
 
 July 
 
 6 
 13 
 20 
 27 
 
 7 
 
 147 
 30 
 69 
 
 10 
 20 
 45 
 86 
 
 27 
 
 172 
 
 J.  1  Ci 
 
 18 
 36 
 
 0 
 0 
 
 0 
 
 3 
 
 Aug. 
 
 3 
 10 
 17 
 23 
 30 
 
 117 
 155 
 129 
 211 
 204 
 
 172 
 278 
 225 
 749 
 760 
 
 47 
 
 63 
 162 
 125 
 209 
 
 8 
 10 
 2 
 0 
 0 
 
 Sept. 
 
 6 
 13 
 20 
 
 222 
 241 
 264 
 
 718 
 1,642 
 Fumigated 
 
 268 
 282 
 160 
 
 0 
 0 
 
 Fumigated 
 
 1/  Through  a  mistake  this  warehouse  was  sprayed  once  with 
 pyrethrum  in  oil. 
 
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 Effect  of  Acrylonitrile-Carbon  Tetrachloride  on  Tobacco 
 
 Repeated  tests  were  made  to  discover  any  possible  effect  of  this 
 fumigant  on  flue-cured  tobacco  or  on  Turkish  tobacco.   Samples  of 
 fumigated  and  unfumigated  tobacco  of  the  same  grade  were  submitted 
 to  leaf -tobacco  experts.   No  effect  upon  the  aroma,  taste,  or  appearance 
 of  the  tobacco  was  noted.   Immediately  after  fumigation  a  very  faint  odor 
 could  sometimes  be  detected,  but  it  vanished  in  less  than  24  hours.  A 
 chemical  analysis  was  made  for  residues  of  acrylonitrile  on  fumigated 
 tobacco.    The  only  method  known  of  making  such  analysis  was  to  pass 
 heated  air  over  the  tobacco  and  then  analyze  the  air  for  free  nitrogen. 
 Tobacco  contains  so  much  free  nitrogen  that  the  figures  obtained  were 
 meaningless . 
 
 Effect  of  Acrylonitrile-Carbon 
 Tetrachloride  on  Equipment 
 
 Acrylonitrile- carbon  tetrachloride  is  corrosive  to  certain  materials. 
 Iron  corrodes  quickly;  hence  it  is  not  satisfactory  to  use  plain  iron  pipes 
 or  containers.   Galvanized  iron  and  tinned  iron  stand  up  satisfactorily 
 for  short  periods.   RUBBER  TUBING  CANNOT  BE  USED,  AS  ACRYLO- 
 NITRILE QUICKLY  POLYMERIZES  AND  DESTROYS  RUBBER.  Stainless 
 steel  tubing  is  most  satisfactory  for  use  in  vacuum  or  atmospheric 
 chambers.    Copper  tubing  has  been  used,  with  little  or  no  evidence  of 
 corrosion  after  3  years.   However,  regardless  of  the  fumigant  used, 
 great  care  should  be  taken  to  blow  out  the  piping  system  thoroughly 
 afterwards.   Apparently  it  is  the  liquid  fumigant  that  is  corrosive,  not 
 the  vapor  phase. 
 
 A  compressor  that  had  been  in  constant  use  for  over  a  year  in 
 connection  with  acrylonitrile- carbon  tetrachloride  fumigation  of  tobacco 
 was  dismantled  for  repairs  in  the  winter  of  1948-49.   Careful  examina- 
 tion of  all  parts  showed  no  corrosion  of  the  steel. 
 
 Although  the  acrylonitrile- carbon  tetrachloride  mixture  is  not  so 
 volatile  as  most  fumigants  and  can  be  shipped  in  regular  galvanized- 
 iron  or  tin  drums,  THE  VAPOR  EVOLVING  FROM  THIS  MIXTURE  IS 
 POISONOUS  AND  THE  MIXTURE  MUST  BE  HANDLED  ACCORDINGLY. 
 
 Summary 
 
 In  extensive  tests  with  atmospheric  and  vacuum  fumigation  a  50-50 
 mixture  of  acrylonitrile-carbon  tetrachloride,  was  found  to  be  a  satis- 
 factory fumigant  for  cigarette-type  tobaccos. 
 
 In  laboratory  tests  at  atmospheric  pressure,  it  was  as  effective  as 
 hydrogen  cyanide  against  cigarette  beetle  larvae,  but  less  effective 
 against  tobacco  moth  larvae.    It  showed  unusual  penetration,  yet  it  aired 
 
-  10  - 
 
 out  rapidly.   No  injury  to  tobacco  was  noted.   In  commercial  atmospheric 
 chambers  at  summer  temperatures  a  dosage  of  20  ounces  per  1,000 
 cubic  feet,  with  an  exposure  of  72  hours,  gave  complete  kill  of  cigarette 
 beetle  larvae  to  a  depth  of  9  inches  in  bales  of  Turkish  tobacco.   In  hogs- 
 heads of  flue -cured  tobacco  a  dosage  of  32  ounces  with  the  same  exposure 
 gave  100  percent  mortality  of  cigarette  beetle  larvae  at  a  depth  of  3  inches, 
 99  percent  at  5  inches,  86  percent  at  7  inches,  and  72  percent  at  9  inches. 
 
 In  large  warehouses  of  flue-cured  tobacco  in  hogsheads  a  dosage  of 
 approximately  40  ounces  per  1,000  cubic  feet,  with  an  exposure  of  72 
 hours,  gave  excellent  results  against  cigarette  beetle  larvae.   In  other 
 warehouses  fumigation  with  hydrogen  cyanide  at  16  ounces  per  1,000 
 cubic  feet  was  less  effective  against  the  tobacco  moth. 
 
 In  small  vacuum  chambers  in  the  laboratory  the  minimum  dosage  of 
 acrylonitrile- carbon  tetrachloride  to  give  complete  kill  of  cigarette 
 beetle  larvae  in  bales  of  Turkish  tobacco  was  20  ounces  per  1,000  cubic 
 feet,  with  a  3 -hour  exposure  and  temperature  of  73°- 8 2° 
 
 In  vacuum  fumigation  in  commercial  chambers  at  temperatures  above 
 60°  F.,  a  dosage  of  48  ounces  of  acrylonitrile-carbon  tetrachloride  per 
 1,000  cubic  feet,  with  an  exposure  of  4  hours,  gave  complete  kill  of 
 cigarette  beetle  larvae  to  a  depth  of  9  inches  in  bales  of  Turkish  tobacco. 
 However,  at  lower  temperatures  (29°-50°)  64  ounces  per  1,000  cubic  feet 
 did  not  give  complete  mortality  in  all  tests.   In  hogsheads  of  flue- cured 
 tobacco  at  summer  temperatures,  64  ounces  per  1,000  cubic  feet,  with 
 an  exposure  of  4  hours,  gave  complete  mortality  of  cigarette  beetle  larvae 
 to  a  depth  of  9  inches. 
 
 No  effect  of  acrylonitrile-carbon  tetrachloride  upon  the  aroma,  taste, 
 or  appearance  of  flue-cured  or  Turkish  tobacco  was  noted. 
 
 In  a  study  of  the  effect  of  acrylonitrile-carbon  tetrachloride  on 
 different  materials,  it  was  found  that  stainless  steel  is  most  satisfactory 
 for  use  in  vacuum  or  atmospheric  chambers;  copper  showed  little  or  nc 
 corrosion  after  3  years;  galvanized  iron  and  tinned  iron  stand  up  for 
 short  periods;  but  plain  iron  is  not  satisfactory.    Rubber  tubing  cannot 
 be  used. 
 
 Literature  Cited 
 
 (1)  Reed,  W.  D.,  and  Vinzant,  J.  P. 
 
 1942.    Control  of  insects  attacking  stored  tobacco  and  tobacco 
 products.    U.  S.  Dept.  Agr.  Cir.  635,  40  pp.,  illus. 
 
 (2)   ,  Livingstone,  E.  M.,  and  Morrill,  A.  W.,  Jr. 
 
 1936.   Apparatus  for  placing  test  lots  of  insects  within  parcels 
 of  stored  tobacco  during  fumigation  experiments.    U.  S. 
 Bur.  Ent.  and  Plant  Quar.  ET-83,  3  pp.,  illus.  /Processed]/