﻿SPRAYING 
  AGAINST 
  GRAPE 
  LEAFHOPPER. 
  13 
  

  

  (See 
  fig. 
  3.) 
  At 
  this 
  time 
  the 
  underside 
  of 
  badly 
  infested 
  leaves 
  will 
  

   be 
  covered 
  by 
  the 
  nymphs 
  in 
  all 
  stages 
  of 
  development. 
  Generally 
  

   speaking, 
  this 
  condition 
  is 
  likely 
  to 
  occur 
  in 
  the 
  Lake 
  Erie 
  Valley 
  from 
  

   July 
  1 
  to 
  15. 
  All 
  of 
  the 
  field 
  experiments 
  conducted 
  in 
  1910 
  and 
  1911 
  

   were 
  made 
  between 
  these 
  dates 
  and 
  in 
  every 
  instance 
  very 
  satisfactory 
  

   results 
  were 
  secured. 
  Since 
  the 
  nymphs 
  continue 
  to 
  hatch 
  over 
  a 
  

   long 
  period, 
  if 
  the 
  spray 
  application 
  is 
  made 
  while 
  the 
  first 
  nymphs 
  

   to 
  hatch 
  are 
  quite 
  small 
  large 
  numbers 
  are 
  likely 
  to 
  hatch 
  after 
  the 
  

   spray 
  application 
  has 
  been 
  made, 
  thus 
  necessitating 
  a 
  second 
  applica- 
  

   tion 
  a 
  few 
  weeks 
  later. 
  On 
  the 
  other 
  hand, 
  if 
  the 
  application 
  is 
  with- 
  

   held 
  until 
  many 
  of 
  the 
  nymphs 
  have 
  developed 
  wings 
  it 
  is 
  doubtful 
  

   if 
  large 
  vineyard 
  areas 
  can 
  be 
  treated 
  before 
  a 
  large 
  percentage 
  of 
  

   the 
  nymphs 
  have 
  reached 
  the 
  winged 
  stage. 
  For 
  it 
  must 
  be 
  under- 
  

   stood 
  that 
  the 
  tobacco 
  extracts 
  at 
  the 
  dilutions 
  recommended 
  are 
  

   effective 
  only 
  against 
  the 
  wingless 
  nymphs 
  infesting 
  the 
  underside 
  of 
  

   the 
  grape 
  foliage. 
  Where 
  it 
  is 
  necessary 
  to 
  treat 
  large 
  areas 
  for 
  this 
  

   pest, 
  observation 
  would 
  indicate 
  that 
  spray 
  applications 
  should 
  

   commence 
  during 
  the 
  first 
  week 
  in 
  July. 
  

  

  Observations 
  on 
  the 
  abundance 
  and 
  the 
  extent 
  of 
  injury 
  wrought 
  

   by 
  this 
  insect 
  pest 
  of 
  the 
  grapevine 
  in 
  the 
  vineyard 
  areas 
  of 
  New 
  York, 
  

   Pennsylvania, 
  and 
  Ohio 
  bordering 
  on 
  Lake 
  Erie, 
  and 
  also 
  in 
  the 
  vine- 
  

   yard 
  areas 
  of 
  Michigan, 
  indicate 
  that 
  its 
  depredations 
  have 
  increased 
  

   during 
  the 
  past 
  few 
  years. 
  Progressive 
  vineyardists 
  are 
  commencing 
  

   to 
  realize 
  that 
  the 
  accumulated 
  injury 
  to 
  the 
  vines- 
  by 
  this 
  pest 
  is 
  

   responsible 
  for 
  curtailment 
  in 
  crop 
  yield 
  and 
  inferiority 
  in 
  quality 
  of 
  

   fruit 
  wherever 
  it 
  is 
  present 
  on 
  grapevines 
  in 
  large 
  numbers 
  and 
  that 
  

   steps 
  must 
  be 
  taken 
  to 
  accomplish 
  its 
  control. 
  It 
  is 
  for 
  this 
  reason 
  

   that 
  the 
  experiments 
  presented 
  in 
  this 
  paper 
  were 
  undertaken, 
  and 
  

   it 
  is 
  hoped 
  that 
  the 
  results 
  obtained 
  are 
  of 
  sufficient 
  commercial 
  value 
  

   to 
  encourage 
  grape 
  growers 
  having 
  vineyard 
  areas 
  infested 
  by 
  the 
  

   grape 
  leafhopper 
  to 
  adopt 
  this 
  method 
  of 
  control. 
  

  

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