﻿12 
  DECIDUOUS 
  FRUIT 
  INSECTS 
  AND 
  INSECTICIDES. 
  

  

  In 
  comparing 
  the 
  sugar 
  content 
  of 
  the 
  samples 
  from 
  the 
  sprayed 
  

   and 
  the 
  unsprayed 
  plats 
  it 
  will 
  be 
  observed 
  that 
  the 
  sample 
  from 
  the 
  

   unsprayed 
  plat 
  under 
  serial 
  No. 
  3154 
  showed 
  a 
  sugar 
  content 
  of 
  only 
  

   8.61 
  grams 
  per 
  100 
  c. 
  c. 
  as 
  against 
  16.18 
  grams 
  per 
  100 
  c. 
  c. 
  for 
  sample 
  

   3153 
  from 
  the 
  sprayed 
  plat. 
  In 
  other 
  words, 
  the 
  sample 
  of 
  grapes 
  

   taken 
  from 
  the 
  plat 
  where 
  the 
  injury 
  to 
  the 
  foliage 
  of 
  the 
  vines 
  by 
  

   the 
  grape 
  leafhopper 
  was 
  unchecked, 
  by 
  withholding 
  the 
  tobacco- 
  

   extract 
  spray 
  against 
  the 
  nymphs, 
  contained 
  only 
  about 
  one-half 
  the 
  

   sugar 
  content 
  that 
  was 
  present 
  in 
  the 
  sample 
  taken 
  from 
  the 
  vines 
  

   which 
  were 
  sprayed 
  with 
  the 
  tobacco 
  against 
  this 
  insect 
  in 
  the 
  

   nymphal 
  stage. 
  Samples 
  under 
  serial 
  No. 
  3156 
  from 
  the 
  unsprayed 
  

   plat 
  show 
  a 
  sugar 
  content 
  of 
  4.66 
  grams 
  per 
  100 
  c. 
  c. 
  less 
  than 
  sample 
  

   No. 
  3155, 
  taken 
  from 
  the 
  sprayed 
  plat, 
  and 
  sample 
  No. 
  3260 
  from 
  

   unsprayed 
  plat 
  shows 
  a 
  sugar 
  content 
  of 
  6.37 
  grams 
  per 
  100 
  c. 
  c. 
  less 
  

   than 
  sample 
  3261, 
  taken 
  from 
  sprayed 
  vines 
  in 
  the 
  same 
  vineyard. 
  

  

  In 
  answer 
  to 
  an 
  inquiry 
  as 
  to 
  the 
  approximate 
  difference 
  in 
  value 
  

   of 
  the 
  fruit 
  from 
  these 
  sprayed 
  and 
  unsprayed 
  plats 
  for 
  use 
  in 
  making 
  

   wine 
  or 
  grape 
  juice 
  Prof. 
  Alwood 
  gives 
  the 
  following 
  reply: 
  

  

  In 
  response 
  to 
  your 
  question 
  I 
  may 
  say 
  that 
  the 
  sugar 
  content 
  of 
  the 
  three 
  untreated 
  

   plats 
  is 
  so 
  low 
  that 
  they 
  would 
  have 
  no 
  value 
  whatever 
  for 
  making 
  pure 
  wine 
  or 
  unfer- 
  

   mented 
  grape 
  juice 
  and 
  could 
  only 
  be 
  used 
  for 
  some 
  low 
  grade 
  sophisticated 
  products. 
  

  

  Thus 
  the 
  analysis 
  of 
  these 
  samples 
  of 
  fruit 
  indicates 
  that 
  serious 
  

   injury 
  to 
  the 
  foliage 
  of 
  the 
  grapevine 
  by 
  the 
  grape 
  leafhopper 
  greatly 
  

   impairs 
  the 
  quality 
  of 
  the 
  fruit. 
  A 
  definite 
  knowledge 
  of 
  this 
  fact 
  

   furnishes 
  an 
  additional 
  reason 
  why 
  the 
  vineyardist 
  should 
  resort 
  to 
  

   every 
  practical 
  means 
  at 
  his 
  disposal 
  for 
  the 
  control 
  of 
  this 
  insect 
  

   whenever 
  it 
  is 
  at 
  all 
  numerous 
  in 
  his 
  vineyard. 
  

  

  CONCLUSION. 
  

  

  The 
  field 
  experiments 
  made 
  during 
  the 
  season 
  of 
  1911 
  against 
  the 
  

   grape 
  leafhopper 
  and 
  recorded 
  in 
  this 
  paper 
  show 
  that 
  a 
  single 
  applica- 
  

   tion 
  of 
  the 
  tobacco 
  extracts 
  applied 
  against 
  this 
  insect 
  in 
  the 
  nymphal 
  

   stage 
  as 
  a 
  contact 
  spray 
  will 
  reduce 
  its 
  numbers 
  to 
  such 
  an 
  extent 
  

   that 
  the 
  infested 
  vines 
  will 
  remain 
  in 
  good 
  foliage 
  throughout 
  the 
  

   season 
  and 
  mature 
  a 
  crop 
  of 
  high-quality 
  fruit. 
  

  

  As 
  indicated 
  by 
  the 
  variation 
  in 
  the 
  time 
  and 
  rapidity 
  in 
  develop- 
  

   ment 
  of 
  the 
  nymphs 
  in 
  1910 
  and 
  1911, 
  it 
  is 
  evident 
  that 
  no 
  definite 
  

   date 
  for 
  making 
  the 
  spray 
  application 
  can 
  be 
  given. 
  Where 
  the 
  

   winged 
  adults 
  are 
  at 
  all 
  numerous 
  in 
  the 
  early 
  part 
  of 
  the 
  season 
  the 
  

   vineyardist 
  is 
  urged 
  to 
  examine 
  the 
  underside 
  of 
  the 
  grape 
  leaves 
  

   toward 
  the 
  middle 
  and 
  the 
  end 
  of 
  June 
  and 
  to 
  observe 
  the 
  number 
  and 
  

   size 
  of 
  the 
  nymphs. 
  The 
  spray 
  application 
  to 
  be 
  most 
  effective 
  

   should 
  be 
  made 
  at 
  about 
  the 
  time 
  the 
  first 
  nymphs 
  to 
  hatch 
  are 
  near 
  

   the 
  last 
  molt. 
  This 
  is 
  indicated 
  by 
  the 
  length 
  of 
  the 
  wing 
  pads. 
  

  

  