﻿14 
  

  

  CIRCULAR 
  2 
  70, 
  U. 
  S. 
  DEPARTMENT 
  OF 
  AGRICULTURE 
  

  

  Since 
  the 
  mites 
  begin 
  feeding 
  in 
  

   the 
  leaves 
  before 
  they 
  are 
  fully 
  

   opened, 
  the 
  new 
  leaves 
  show 
  the 
  

   blisters 
  at 
  once; 
  and 
  if 
  the 
  mites 
  

   are 
  numerous, 
  many 
  of 
  the 
  leaves 
  

   later 
  dry 
  and 
  drop 
  off. 
  The 
  fruit 
  

   of 
  the 
  apple 
  is 
  more 
  seriously 
  af- 
  

   fected 
  than 
  that 
  of 
  the 
  pear 
  ; 
  it 
  is 
  

   attacked 
  when 
  it 
  is 
  young, 
  and 
  the 
  

   injuries 
  cause 
  mature 
  fruit 
  to 
  be 
  

   russeted 
  or 
  deformed 
  (fig. 
  15, 
  5) 
  

   and 
  sometimes 
  to 
  crack 
  open. 
  The 
  

   mites 
  also 
  injure 
  and 
  deform 
  the 
  

   blossoms. 
  

  

  There 
  is 
  some 
  evidence 
  that 
  the 
  

   mites 
  attacking 
  apple 
  and 
  pear 
  

   are 
  distinct 
  species. 
  Often 
  apples 
  

   will 
  be 
  injured 
  but 
  pears 
  on 
  ad- 
  

   jacent 
  trees 
  will 
  show 
  no 
  injury. 
  

   The 
  mite 
  that 
  attacks 
  the 
  apple 
  

   apparently 
  comes 
  from 
  the 
  wild 
  

   snowberry, 
  since 
  a 
  mite 
  that 
  seems 
  

   to 
  be 
  identical 
  is 
  found 
  on 
  that 
  

   plant, 
  and 
  apple 
  orchards 
  in 
  can- 
  

   yons 
  and 
  along 
  foothills 
  near 
  

   wild 
  growths 
  of 
  the 
  snowberry 
  are 
  

   most 
  often 
  infested. 
  The 
  form 
  

   found 
  on 
  the 
  pear 
  tree 
  is 
  evidently 
  

   the 
  same 
  as 
  the 
  species 
  occurring 
  

   in 
  Europe, 
  and 
  undoubtedly 
  came 
  

   from 
  there. 
  

  

  LIFE 
  HISTORY 
  

  

  The 
  adults 
  winter 
  under 
  the 
  

   scales 
  of 
  fruit 
  and 
  leaf 
  buds. 
  

   They 
  are 
  exceedingly 
  small, 
  less 
  

   than 
  one 
  one-hundredth 
  inch 
  

   long. 
  Under 
  a 
  lens 
  they 
  appear 
  

   as 
  elongated, 
  whitish, 
  wormlike 
  

   creatures, 
  with 
  four 
  legs 
  near 
  the 
  

   head 
  end 
  (fig. 
  15, 
  C). 
  Often 
  hun- 
  

   dreds 
  of 
  them 
  can 
  be 
  found 
  in 
  a 
  

   single 
  bud. 
  In 
  warm 
  spring 
  

   weather 
  when 
  the 
  buds 
  begin 
  to 
  

   swell 
  the 
  mites 
  lay 
  eggs 
  in 
  them, 
  

   and 
  the 
  young 
  burrow 
  into 
  the 
  

   unfolding 
  leaves 
  and 
  form 
  the 
  

   characteristic 
  blisters. 
  They 
  feed 
  

   entirely 
  within 
  the 
  blisters, 
  and 
  a 
  

   succession 
  of 
  generations 
  develop, 
  

   practically 
  out 
  of 
  the 
  reach 
  of 
  

   sprays. 
  With 
  the 
  approach 
  of 
  

   cold 
  weather 
  the 
  mites 
  migrate 
  to 
  

  

  the 
  buds, 
  where 
  they 
  hibernate 
  

   beneath 
  the 
  scales. 
  

  

  CONTROL 
  

  

  The 
  pear 
  leaf 
  blister 
  mite 
  can 
  

   be 
  controlled 
  easily 
  with 
  liquid 
  

   lime- 
  sulfur 
  used 
  as 
  a 
  dormant 
  

   spray 
  at 
  the 
  same 
  strength 
  as 
  for 
  

   the 
  San 
  Jose 
  scale 
  — 
  ^that 
  is, 
  testing 
  

   41/2° 
  Baume 
  (table 
  1, 
  p. 
  60). 
  If 
  

   the 
  San 
  Jose 
  scale 
  is 
  not 
  present, 
  

   the 
  lime-sulfur 
  need 
  test 
  only 
  3i/^° 
  

   Baume. 
  Spraying 
  should 
  be 
  com- 
  

   pleted 
  in 
  the 
  spring 
  before 
  the 
  

   buds 
  have 
  begun 
  to 
  open, 
  for 
  the 
  

   mites 
  get 
  into 
  the 
  leaves 
  soon 
  after 
  

   that 
  and 
  cannot 
  be 
  reached 
  with 
  

   the 
  spray. 
  Good 
  control 
  may 
  also 
  

   be 
  obtained 
  by 
  spraying 
  in 
  the 
  

   fall, 
  as 
  soon 
  as 
  the 
  leaves 
  have 
  

   dropped. 
  Oil 
  emulsions 
  are 
  not 
  

   effective 
  unless 
  aj)plied 
  just 
  as 
  

   the 
  buds 
  are 
  swelling 
  noticeably; 
  

   the 
  weather 
  must 
  be 
  warm 
  so 
  that 
  

   the 
  oil 
  will 
  penetrate 
  into 
  the 
  buds 
  

   and 
  kill 
  the 
  mites. 
  

  

  Apple 
  Rust 
  Mite 
  

  

  A 
  very 
  small 
  mite, 
  not 
  unlike 
  

   the 
  pear 
  leaf 
  blister 
  mite, 
  is 
  often 
  

   found 
  on 
  the 
  under 
  surfaces 
  of 
  

   apple 
  and 
  pear 
  leaves 
  as 
  well 
  as 
  on 
  

   prune 
  leaves. 
  This 
  is 
  the 
  apple 
  

   rust 
  mite, 
  so 
  named 
  because 
  its 
  

   feeding 
  gives 
  the 
  leaves 
  a 
  rusty 
  

   appearance. 
  It 
  also 
  causes 
  the 
  

   leaves 
  to 
  roll 
  lengthwise. 
  The 
  

   fruit 
  may 
  be 
  attacked 
  and 
  become 
  

   russeted. 
  

  

  The 
  apple 
  rust 
  mite 
  is 
  so 
  small 
  

   that 
  it 
  can 
  scarcely 
  be 
  seen 
  with 
  

   the 
  naked 
  eye. 
  Under 
  a 
  lens 
  it 
  is 
  

   found 
  to 
  be 
  shorter 
  and 
  more 
  tri- 
  

   angular 
  than 
  the 
  pear 
  leaf 
  blister 
  

   mite. 
  Instead 
  of 
  producing 
  blis- 
  

   ters, 
  this 
  mite 
  feeds 
  on 
  the 
  leaf 
  

   surface 
  during 
  the 
  growing 
  season 
  

   and 
  hibernates 
  in 
  the 
  buds. 
  It 
  

   may 
  be 
  controlled 
  by 
  the 
  same 
  

   means 
  used 
  for 
  the 
  blister 
  mite. 
  

   Contact 
  sprays, 
  such 
  as 
  those 
  used 
  

   for 
  control 
  of 
  orchard 
  mites 
  (p. 
  

   12), 
  applied 
  during 
  the 
  summer 
  

  

  