LIBRARY 
 STATE  PLANT  BOARD 
 
 September  1945  E-671 
 
 United  States  Department  of  Agriculture 
 Agricultural  Research  Administration 
 Bureau  of  Entomology  and  Plant  Quarantine 
 
 THE  EFFECTS  OF  DDT  DUST  AND  SPRAY  PREPARATIONS 
 ON  LARVAE  OF  THE  EUROPEAN  CORN  BORER 
 
 By  D.  D.  Questel,  Division  of  Cereal  and  Forage  Insect  Investigations 
 
 During  the  winter  of  19Uh-U5  laboratory  experiments  were  conducted 
 with  a  number  of  DDT  dusts  to  determine  the  effects  of  different  particle 
 sizes,  diluents,  and  concentrations  of  DDT  on  hibernating  and  actively 
 feeding  larvae  of  the  European  corn  borer  (Pyrausta  nubilalis  (Hbn.)). 
 The  results  of  these  studies  and  their  relation  to  field  experiments  con- 
 ducted during  the  season  of  19*+h  are  presented  herein. 
 
 Experiment  With  Hibernating  Larvae 
 
 In  this  experiment  various  DDT  dusts  were  compared  with  lead 
 arsenate  and  rotenone  dusts.    Approximately  0.5  gram  of  each  preparation 
 to  be  tested  was  placed  in  each  of  ten  2-inch  glass  vials.    A  single 
 hibernating  larva,  which  had  been  collected  during  October  and  held  in 
 storage  for  2  months  at  38°  F. ,  was  placed  in  each  vial.    The  vials  were 
 shaken  so  as  to  cover  the  larvae  thoroughly  with  dust.    They  were  then 
 stoppered  with  a  plug  of  cellulose  fiber  and  placed  in  an  incubator  where 
 the  temperature  remained  constant  at  86°.    No  attempt  was  made  to  control 
 the  humidity.    All  tests  were  duplicated.    The  number  of  dead  larvae  was 
 recorded  every  2U  hours. 
 
 Various  characteristics  of  these  dusts,  as  determined  by  the  Division 
 of  Insecticide  Investigations,  are  given  in  taJble  1.    The  bulk  measure- 
 ments were  made  with  the  Scott  volumeter. 
 
 From  the  data  in  table  2  it  is  apparent  that  particle  size  is  of  some 
 importance,  since  all  micronized  dusts  were  more  efficient  than  the  micro- 
 pulverized  dusts  containing  the  same  diluent.    However,  it  is  evident  that 
 other  factors  related  to  the  carrier  itself  were  operating,  since  the 
 micronized  talc  mixture,  although  having  a  smaller  mean  diameter  than  the 
 mi cr ©pulverized  clay  or  diatomaceous  earth  mixture,  was  less  toxic  than 
 either  of  them.    Of  the  three  diluents  used  in  the  50-percent  DDT  dusts, 
 the  clay  and  diatomaceous  eartn  were  much  more  efficient  than  the  talc. 
 
 OCT  6-  1945 
 
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 The  relatively  high  efficiency  of  the  10.8  percent  DDT-pyrophyl- 
 lite  dust  in  comparison  with  the  other  mixtures  Is  in  agreement  with 
 the  results  obtained  with  this  material  in  spray  form  in  previous 
 tests  against  feeding  larvae,!/  and  is  in  strong  contrast  with  the 
 extremely  low  mortality  caused  by  the  undiluted  DDT  powder*    The  lack 
 of  effectiveness  of  the  5  percent  DDT  in  an  unknown  carrier  is^  in 
 general  agreement  with  previous  results  obtained  in  the  field,!/  where 
 it  was  less  effective  than  either  the  10*8  percent  DDT-pyrophyllite  or 
 the  undiluted  DDT,  all  applied  as  spray  suspensions  in  approximately 
 the  same  concentration  of  DDT* 
 
 The  ground  derris  root  killed  all  the  larvae  within  2k  hours,  hut 
 these  larvae,  in  contrast  to  those  killed  by  some  of  the  DDT  prepara- 
 tions, remained  soft  and  normal  in  size.   Lead  arsenate  caused  no  mor- 
 tality until  the  fourth  day,  when  only  5  percent  were  dead,  and  it  did 
 not  cause  any  additional  mortality  on  the  fifth  day* 
 
 0 
 
 Pyrophyllite  alone  caused  no  mortality  and  thus  demonstrated  that 
 this  diluent  in  itself  was  not  responsible  for  the  greater  effective- 
 ness of  the  10,8  percent  DDT-pyrophyllite  dust  than  that  caused  by  the 
 undiluted  DDT*    What  physical  or  chemical  characteristics  of  the  .mixture 
 were  responsible  for  its  much  higher  toxicity  are  not  known.    The  com- 
 parative efficiency  of  the  different  mixtures  tested  apparently  was 
 associated  with  both  particle  size  and  identity  of  the  diluents  they 
 contained* 
 
 Experiments  With  Feeding  Larvae 
 
 The  results  of  two  feeding  experiments,  one  in  the  laboratory  and 
 one  in  the  field,  to  determine  the  toxicity  of  different  DDT  dusts  used 
 in  spray  suspensions  to  newly  hatched  corn  borer  larvae  are  given  in 
 tables  3  end  U*    The  comparative  efficiency  of  the  materials  tested 
 against  feeding  larvae  was  similar  to  that  shown  by  the  tests  with 
 hibernating  larvae*    These  results  suggest  that  for  field  use  against 
 the  European  corn  borer  a  micronized  DDT-absorbent  clay  mixture  would 
 be  the  most  satisfactory  of  any  of  the  preparations  tested* 
 
 1/  Satchelder,  C.  H.,  and  Quest  el,  D*  D.  19^5.    Experiments  with 
 DDT  for  the  control  of  the  European  corn  borer  infesting  sweet  com  at 
 Toledo,  Ohio,  in  lpM.    U.S.  Bur.  Ent.  and  Plant  Quar.  B-659,  11  PP» 
 
 > 
 
Table  3.— Effect  on  newly  hatched  larvae  of  exposure  for  a  H8-hour  period 
 to  cauliflower  leaves  sprayed  with  various  DDT  preparations. 
 Laboratory  tests 
 
 Concentration 
 of  DDT, 
 percent 
 
 Diluent 
 
 Average  percent  mortality  of  larvae  exposed  to 
 indicated  amount  of  DDT  per  100  gallons  of  water 
 
 0.2H 
 
 0.12 
 
 0.06 
 
 0.03 
 
 0.015 
 
 O.OO75 
 
 pound 
 
 pound 
 
 pound 
 
 pound 
 
 pound 
 
 pound 
 
 50 
 
 Absorbent  clay 
 (micron! zed) 
 
 100.0 
 
 100.0 
 
 99.0 
 
 62.9 
 
 13.3 
 
 10.8 
 
 Pyrophyllite 
 
 100.0 
 
 98.3 
 
 16.2 
 
 l.U 
 
 0 
 
 100 
 
 Hone 
 
 93.2 
 
 83.0 
 
 36.8 
 
 6.0 
 
 0 
 
 0 
 
 5 
 
 Unknown 
 
 96.3 
 
 U.2 
 
 2.2 
 
 0 
 
 1.7 
 
 50 
 
 Fibrous  talc 
 (micro- 
 
 100.0 
 
 92.6 
 
 11.2 
 
 5.3 
 
 0 
 
 0 
 
 pulverised) 
 
 Table  k. — Effectiveness  of  various  DDT  preparations  against  larvae  infesting 
 early-market  sweet  corn.    Held  tests,  Toledo,  Ohio,  19*& 
 
 Concen- 
 tration 
 of  DDT 
 
 Diluent 
 
 DDT  per 
 100  gal- 
 lons of 
 water 
 
 Larvae 
 
 deduction  of  borers 
 
 Per  100 
 plants 
 
 In  ears  from 
 100  plants 
 
 Per  100 
 plants 
 
 In  ears  from 
 100  plants 
 
 Percent 
 
 Pound 
 
 Number 
 
 number 
 
 Percent 
 
 Percent 
 
 10.8 
 
 Pyrophyllite 
 
 O.U32 
 
 3« 
 
 U 
 
 97.9 
 
 99.2 
 
 100 
 
 Vone 
 
 .50 
 
 70 
 
 20 
 
 96.2 
 
 96.0 
 
 5 
 
 Unknown 
 
 .UO 
 
 11U 
 
 36 
 
 93.8 
 
 92.7 
 
 Cheek 
 
 IS3U 
 
 U96 
 
 (untreated) 
 
6 
 
 Action  of  Toxic  Agent  on  Hibernating  Larvae 
 
 A  striking  effect  of  the  DDT  dusts  that  killed  the  larvae  in  a 
 comparatively  short  time  was  a  shrinking,  desiccation,  and  hardening 
 of  the  larvae*    When  death  did  not  occur  rapidly,  however,  as  in  the 
 treatments  utilizing  undiluted  DDT,  shrinking  and  hardening  did  not 
 take  place  even  though  convulsive  movements  and  partial  paralysis 
 were  evident*    The  rapid  mortality  caused  by  ground  derris  root  showed 
 no  evidence  of  shrinking,  desiccation,  and  hardening*    The  contrast  in 
 appearance  of  larvae  killed  quickly  by  DDT  and  by  derris  is  shown  in 
 figure  1*    The  characteristic  shrinking  and  hardening  of  the  larvae 
 subjected  to  the  rapidly  killing  DDT  mixtures  may  provide  a  clue  to 
 the  manner  in  which  the  active  agent  in  these  mixtures  causes  death* 
 
 Discussion 
 
 It  seems  of  particular  interest  to  note  from  the  foregoing  obser- 
 vations that  (l)  the  percentage  of  DDT  in  a  dust  appeared  to  have  less 
 effect  on  toxicity  than  the  physical  and  chemical  character  of  the 
 mixture  of  DDT  and  diluent,  (2)  rapidly  killing  DDT  dust  mixtures 
 caused  a  definite  shrinking  and  hardening  of  the  hibernating  larvae, 
 whereas  ground  derris  powder  that  killed  equally  as  rapidly  did  not, 
 (3)  the  toxicity  of  the  various  materials  tested  as  contact  poisons 
 against  hibernating  larvae  closely  paralleled  that  obtained  in  feeding 
 tests  against  newly  hatched  larvae  in.  the  laboratory  and  against  young 
 larvae  infesting  sweet  com  in  the  field,  in  those  cases  where  both 
 types  of  tssts  were  conducted,  and  (h)  a  group  of  mixtures  containing 
 an  active  agent  which  kills  by  contact  can  perhaps  he  evaluated  readily 
 "by  laboratory  tests  to  determine  their  effects  on  hibernating  larvae* 
 
 Experiments  with  several  DDT  dust  and  spray  preparations  conducted 
 against  "both  hibernating  and  actively  feeding  larvae  of  the  European 
 corn  borer  (Pyrausta  nubilalis  (Hon*))  indicate  that  the  percentage  of 
 DDT  (l- tr ichlor o-2 , 2-bi s (p-chlorophenyl ) ethane)  may  have  less  bearing 
 on  the  effectiveness  of  the  dusts  and  sprays  than  some  other  factors 
 perhaps  related  to  the  physical  or  chemical  character  of  the  diluent* 
 Hibernating  larvae  thoroughly  coated  with  a  powder  containing  10*8  per- 
 cent of  DDT  in  pyrophyllite,  or  with  5°  percent  of  DDT  micronized  with 
 an  absorbent  clay  or  diatomaceous  earth,  were  all  killed  within  3  days, 
 whereas  none,  or  not  more  than  5  percent, of  those  coated  with  powders 
 containing  50  percent  of  DDT   mlcropulverised  with  a  fibrous  talc,  or 
 with  coarsely  ground  undiluted  technical  DDT,  were  killed  within  5  days* 
 The  toxicity  of  the  various  mixtures  to  hibernating  larvae  closely  par- 
 alleled that  obtained  in  feeding  tests  against  newly- hatched  larvae  in 
 the  laboratory  and  against  larvae  infesting  sweet  corn  in  the  field* 
 Rapidly  killing  DDT  dusts  caused  definite  and  characteristic  shrinking* 
 desiccation,  and  hardening  of  the  larvae*    Larvae  killed  as  rapidly  by 
 ground  derris  powder  (H.S  percent  rotenone)  remained  soft  and  normal  in 
 size. 
 
7 
 
 Figure  1#— Hibernating  European  corn  "borer  larvae  killed  within 
 2U  hours  by  exposure  at  86    F.    to  two  insecticidal  dusts:  Left, 
 larvae  killed  with  a  dust  containing  50  percent  of  DDT.  Right, 
 larvae  killed  with  a  ground  derris  root  powder  (h#g  percent  rotenone). 
 
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