﻿ORCHARD 
  INSECTS 
  PACIFIC 
  NORTHWEST 
  

  

  17 
  

  

  grates 
  from 
  tree 
  to 
  tree, 
  additional 
  

   sprays 
  may 
  be 
  necessary, 
  partic- 
  

   ularly 
  on 
  young 
  trees 
  or 
  on 
  nursery 
  

   stock. 
  

  

  Woolly 
  Apple 
  Aphid 
  

  

  The 
  woolly 
  apple 
  aphid 
  attacks 
  

   the 
  roots 
  as 
  well 
  as 
  the 
  upper 
  parts 
  

   of 
  the 
  trees. 
  Above 
  the 
  ground 
  it 
  

   is 
  found 
  chiefly 
  on 
  the 
  trunks, 
  

   limbs, 
  and 
  twigs 
  in 
  wounds 
  caused 
  

   by 
  pruning 
  or 
  cultivating 
  imple- 
  

   ments, 
  and 
  w^herever 
  the 
  bark 
  is 
  

   tender 
  (fig. 
  19). 
  Twigs 
  become 
  

   somewhat 
  swelled 
  and 
  knotted 
  

   from 
  its 
  attacks. 
  The 
  aphids 
  are 
  

   occasionally 
  found 
  on 
  the 
  fruit 
  

   stems 
  and 
  in 
  the 
  calyx 
  ends 
  of 
  

   apples. 
  In 
  the 
  arid, 
  sandy 
  areas 
  

   of 
  the 
  Northwest 
  roots 
  are 
  not 
  

   often 
  injured, 
  the 
  injury 
  being 
  

   usually 
  limited 
  to 
  exposed 
  roots. 
  

   In 
  the 
  coastal 
  sections, 
  particu- 
  

  

  Figure 
  19. 
  — 
  Aerial 
  colony 
  of 
  the 
  woolly 
  

   apple 
  aphid. 
  

  

  larly 
  in 
  heavy 
  soil 
  that 
  may 
  crack, 
  

   the 
  aphids 
  penetrate 
  to 
  the 
  roots, 
  

   causing 
  swellings 
  and 
  other 
  de- 
  

   formities 
  (fig. 
  20) 
  that 
  may 
  hinder 
  

   the 
  growth 
  of 
  the 
  tree. 
  The 
  col- 
  

   onies 
  of 
  aphids 
  appear 
  as 
  bluish- 
  

   white, 
  woolly 
  patches, 
  which 
  are 
  

   composed 
  of 
  the 
  reddish 
  insects 
  

   covered 
  with 
  woolly 
  masses 
  of 
  wax. 
  

   When 
  the 
  aphids 
  are 
  numerous, 
  

   this 
  waxy 
  material, 
  which 
  contains 
  

  

  890478°— 
  50 
  3 
  

  

  some 
  honeydew 
  excreted 
  by 
  the 
  in- 
  

   sects, 
  hangs 
  in 
  festoons, 
  smears 
  the 
  

   fruit, 
  and 
  makes 
  picking 
  a 
  dis- 
  

   agreeable 
  job. 
  In 
  districts 
  where 
  

   the 
  perennial 
  canker 
  disease 
  oc- 
  

   curs, 
  aphids 
  feeding 
  above 
  ground 
  

   apparently 
  prevent 
  the 
  healing 
  of 
  

   cankers. 
  The 
  wooly 
  aphid 
  is 
  

   found 
  in 
  practically 
  all 
  apple- 
  

   growing 
  districts. 
  

  

  Figure 
  20. 
  — 
  Nodular 
  apple 
  roots 
  result- 
  

   ing 
  from 
  attack 
  by 
  the 
  woolly 
  apple 
  

   aphid. 
  

  

  LIFE 
  HISTORY 
  

  

  The 
  woolly 
  apple 
  aphid 
  Hiber- 
  

   nates 
  on 
  the 
  roots 
  of 
  apple 
  

   trees, 
  and 
  many 
  of 
  those 
  on 
  the 
  

   upper 
  portions 
  of 
  the 
  trees 
  also 
  

   survive 
  mild 
  winters. 
  Infesta- 
  

   tions 
  above 
  ground 
  may 
  thus 
  come 
  

   from 
  wintering 
  forms 
  already 
  

   present 
  there 
  or 
  from 
  migrants 
  

   from 
  the 
  roots. 
  Heavy 
  infesta- 
  

   tions 
  are 
  likely 
  to 
  follow 
  mild 
  

   winters. 
  The 
  aphids 
  multiply 
  

   rapidly, 
  and 
  new 
  colonies 
  are 
  es- 
  

   tablished 
  by 
  winged 
  forms 
  flying 
  

   to 
  other 
  apple 
  trees 
  or 
  by 
  young 
  

   aphids 
  carried 
  from 
  tree 
  to 
  tree 
  by 
  

   the 
  wind 
  or 
  by 
  other 
  means. 
  

  

  CONTROL 
  

  

  The 
  establishment 
  of 
  a 
  parasite, 
  

   Aphelinus 
  mali 
  (Hald.), 
  in 
  the 
  

   Pacific 
  Northwest 
  has 
  made 
  it 
  un- 
  

   necessary 
  to 
  use 
  sprays 
  for 
  the 
  

  

  