﻿2 
  

  

  DECIDUOUS 
  FRUIT 
  INSECTS 
  AND 
  INSECTICIDES. 
  

  

  Fig. 
  2.— 
  The 
  grape 
  leaf- 
  

   hopper: 
  Nymph 
  of 
  

   the 
  first 
  stage 
  . 
  Great- 
  

   ly 
  enlarged. 
  

   (Author's 
  illustra- 
  

   tion.) 
  

  

  wings 
  (figs. 
  2-3) 
  that 
  it 
  is 
  most 
  readily 
  controlled 
  by 
  a 
  contact 
  spray, 
  

   it 
  was 
  necessary 
  to 
  make 
  the 
  application 
  several 
  days 
  earlier 
  than 
  in 
  

   the 
  preceding 
  season. 
  In 
  addition 
  to 
  this, 
  the 
  number 
  of 
  days 
  when 
  

   the 
  maximum 
  number 
  of 
  nymphs 
  was 
  present 
  upon 
  the 
  vines 
  before 
  

   the 
  earliest 
  to 
  hatch 
  had 
  developed 
  wings 
  was 
  materially 
  lessened, 
  

   thus 
  shortening 
  the 
  period 
  during 
  which 
  the 
  greatest 
  

   efficiency 
  from 
  the 
  spray 
  applications 
  could 
  be 
  se- 
  

   cured. 
  In 
  1910 
  the 
  maximum 
  numbers 
  of 
  nymphs 
  

   of 
  the 
  first 
  brood 
  were 
  present 
  on 
  the 
  underside 
  of 
  

   the 
  grape 
  leaves 
  about 
  July 
  15 
  and 
  spray 
  applica- 
  

   tions 
  were 
  commenced 
  at 
  that 
  date 
  and 
  were 
  con- 
  

   tinued 
  until 
  July 
  26 
  before 
  many 
  of 
  the 
  nymphs 
  

   had 
  changed 
  to 
  adults 
  having 
  fully 
  developed 
  wings. 
  

   In 
  1911, 
  however, 
  the 
  maximum 
  numbers 
  of 
  

   nymphs 
  were 
  present 
  on 
  the 
  leaves 
  by 
  July 
  5. 
  By 
  

   July 
  11 
  fully 
  15 
  per 
  cent 
  of 
  the 
  first 
  nymphs 
  to 
  

   hatch 
  were 
  changed 
  to 
  the 
  winged 
  form. 
  Thus 
  there 
  was 
  about 
  a 
  

   week 
  longer 
  time 
  during 
  which 
  the 
  greatest 
  efficiency 
  from 
  the 
  

   spray 
  application 
  could 
  be 
  secured 
  in 
  the 
  season 
  of 
  1910 
  than 
  in 
  

   1911. 
  Effective 
  work 
  can 
  be 
  done, 
  however, 
  after 
  many 
  of 
  the 
  

   nymphs 
  have 
  developed 
  wings, 
  and 
  if 
  the 
  wingless 
  nymphs 
  are 
  still 
  

   quite 
  numerous 
  upon 
  the 
  leaves 
  the 
  work 
  may 
  be 
  continued 
  with 
  

   good 
  results. 
  Owing 
  to 
  the 
  more 
  rapid 
  development 
  of 
  the 
  immature 
  

   stages 
  of 
  the 
  insect 
  in 
  1911 
  than 
  in 
  1910, 
  

   there 
  was 
  a 
  partial 
  second 
  brood 
  of 
  consid- 
  

   erable 
  proportions 
  in 
  1911, 
  which 
  greatly 
  

   augmented 
  the 
  injury 
  toward 
  the 
  ripening 
  

   season. 
  Nevertheless, 
  where 
  vines 
  were 
  

   thoroughly 
  sprayed 
  against 
  the 
  nymphs 
  of 
  

   the 
  first 
  brood 
  during 
  the 
  first 
  two 
  weeks 
  in 
  

   July, 
  only 
  slight 
  injury 
  resulted 
  from 
  the 
  

   later 
  development 
  of 
  nymphs 
  on 
  these 
  

   sprayed 
  vines. 
  

  

  FIELD 
  EXPERIMENTS 
  WITH 
  TOBACCO 
  EX- 
  

   TRACTS. 
  

  

  Fig. 
  3.— 
  The 
  grape 
  leafhopper: 
  

   Fully 
  developed 
  nymph 
  of 
  the 
  

   fifth 
  stage. 
  Greatly 
  enlarged. 
  

   (Author's 
  illustration.) 
  

  

  During 
  the 
  summer 
  of 
  1911 
  several 
  field 
  

   experiments, 
  in 
  each 
  case 
  covering 
  several 
  

   acres, 
  were 
  conducted 
  in 
  vineyards 
  in 
  the 
  

   township 
  of 
  North 
  East, 
  Pa. 
  In 
  all 
  cases 
  the 
  applications 
  were 
  

   made 
  against 
  the 
  nymphs 
  about 
  the 
  time 
  the 
  maximum 
  number 
  of 
  

   the 
  first 
  brood 
  was 
  present 
  on 
  the 
  underside 
  of 
  the 
  grape 
  leaves 
  and 
  

   before 
  many 
  of 
  the 
  oldest 
  nymphs 
  had 
  changed 
  to 
  the 
  winged 
  form. 
  

   One 
  thorough 
  application 
  at 
  this 
  time 
  proved 
  sufficient 
  to 
  reduce 
  the 
  

  

  