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  scale 
  in 
  Maryland,* 
  seem 
  to 
  sustain 
  this 
  recommendation. 
  The 
  general 
  

   judgment 
  of 
  economic 
  entomologists 
  will, 
  however, 
  doubtless 
  support 
  

   the 
  following 
  statement 
  quoted 
  from 
  a 
  letter 
  by 
  Dr. 
  L. 
  O. 
  Howard, 
  writ- 
  

   ten 
  December 
  14, 
  189S. 
  

  

  " 
  While 
  hydrocyanic 
  acid 
  gas 
  furnishes 
  the 
  most 
  effective 
  means 
  

   of 
  destroying 
  the 
  San 
  Jose 
  scale 
  and 
  many 
  other 
  scale 
  insects, 
  it 
  is 
  not, 
  

   as 
  some 
  seem 
  to 
  suppose, 
  an 
  absolutely 
  perfect 
  remedy, 
  and 
  experience 
  

   for 
  many 
  years 
  has 
  fully 
  demonstrated, 
  and 
  also 
  experience 
  in 
  the 
  East, 
  

   that 
  here 
  and 
  there 
  an 
  occasional 
  scale 
  will 
  escape 
  this 
  treatment, 
  and, 
  

   in 
  the 
  course 
  of 
  two 
  or 
  three 
  years, 
  it 
  will 
  be 
  necessary 
  to 
  go 
  over 
  the 
  

   plants 
  again. 
  In 
  California, 
  treatments 
  are 
  found 
  to 
  be 
  necessary 
  about 
  

   every 
  three 
  years. 
  Where 
  the 
  work 
  is 
  done 
  with 
  exceptional 
  care, 
  per- 
  

   haps 
  a 
  longer 
  period 
  of 
  immunity 
  is 
  sometimes 
  gained." 
  

  

  In 
  brief, 
  the 
  San 
  Jose 
  scale 
  can 
  clearly 
  be 
  kept 
  in 
  check 
  by 
  thor- 
  

   ough 
  spraying 
  with 
  whale-oil 
  soap 
  or 
  by 
  general 
  fumigation 
  with 
  hydro- 
  

   cyanic 
  gas 
  once 
  in 
  two 
  to 
  four 
  years, 
  according 
  to 
  the 
  situation 
  and 
  the 
  

   rapidity 
  of 
  its 
  multiplication; 
  but 
  it 
  can 
  be 
  exterminated 
  where 
  it 
  has 
  

   once 
  effected 
  a 
  lodgment 
  only 
  by 
  drastic 
  measures 
  of 
  destruction 
  sup- 
  

   plemented 
  by 
  careful 
  spraying 
  or 
  fumigation, 
  or 
  by 
  repeated 
  treatment 
  

   applied 
  in 
  every 
  case 
  just 
  as 
  soon 
  and 
  just 
  as 
  frequently 
  as 
  a 
  watchful 
  

   inspection 
  gives 
  any 
  evidence 
  of 
  the 
  presence 
  of 
  the 
  scale. 
  

  

  Difficulties 
  of 
  Cooperation. 
  

  

  The 
  state 
  legislature, 
  as 
  has 
  already 
  been 
  said, 
  rejected 
  in 
  1897 
  a 
  plan 
  

   of 
  legal 
  and 
  authoritative 
  control 
  and 
  substituted 
  therefor 
  a 
  mere 
  appro- 
  

   priation 
  to 
  the 
  State 
  Entomologist, 
  who 
  was 
  thus 
  provided 
  with 
  funds 
  

   for 
  an 
  investigation 
  and 
  destruction 
  of 
  the 
  San 
  Jose 
  scale, 
  but 
  was 
  left 
  

   without 
  authority 
  to 
  compel 
  action 
  on 
  the 
  part 
  of 
  reluctant 
  owners, 
  or 
  

   to 
  proceed 
  to 
  act 
  in 
  opposition 
  to 
  their 
  wishes. 
  The 
  success 
  of 
  the 
  

   work 
  of 
  destruction 
  was 
  consequently 
  dependent 
  upon 
  volunteer 
  co- 
  

   operation 
  between 
  the 
  Entomologist's 
  office 
  and 
  the 
  citizens 
  most 
  im- 
  

   mediately 
  concerned. 
  There 
  was 
  commonly 
  no 
  difficulty 
  in 
  securing 
  

   such 
  cooperation, 
  at 
  least 
  in 
  the 
  form 
  of 
  permission 
  to 
  enter 
  upon 
  

   premises 
  and 
  the 
  contribution 
  of 
  a 
  considerable 
  amount 
  of 
  labor 
  in 
  the 
  

   application 
  of 
  insecticides. 
  It 
  was 
  much 
  more 
  difficult, 
  however, 
  to 
  

   induce 
  the 
  responsible 
  owner 
  to 
  share 
  in 
  any 
  way 
  the 
  expense 
  of 
  opera- 
  

   tion, 
  some 
  refusing 
  absolutely, 
  declining 
  to 
  acknowledge 
  any 
  responsi- 
  

   bility 
  to 
  the 
  community; 
  others 
  declining 
  to 
  bear 
  any 
  share 
  of 
  the 
  

   expense 
  until 
  satisfied 
  that 
  the 
  insecticide 
  operation 
  was 
  fully 
  successful; 
  

   and 
  still 
  others 
  agreeing, 
  but 
  neglecting, 
  either 
  to 
  purchase 
  the 
  insecti- 
  

   cides 
  or 
  to 
  pay 
  for 
  them 
  when 
  furnished, 
  as 
  proposed 
  in 
  my 
  office 
  circu- 
  

  

  *Bull. 
  No. 
  57, 
  Md. 
  Agr. 
  Exper. 
  Station, 
  Aug., 
  189S. 
  

  

  