﻿ORCHARD 
  INSECTS 
  PACIFIC 
  NORTHWEST 
  

  

  39 
  

  

  Other 
  Borers 
  

  

  Flatheaded 
  borers 
  are 
  often 
  

   found 
  in 
  the 
  trunks 
  of 
  prune 
  

   trees, 
  particularly 
  in 
  unhealthy 
  

   trees. 
  A 
  darkened 
  area 
  of 
  bark 
  

   indicates 
  the 
  presence 
  of 
  these 
  

   borers. 
  The 
  shot 
  -hole 
  borers 
  also 
  

   attack 
  unhealthy 
  trees, 
  making 
  

   round, 
  shotlike 
  holes 
  in 
  the 
  trunks. 
  

   These 
  pests 
  are 
  discussed 
  on 
  pages 
  

   22 
  and 
  23. 
  

  

  Pear 
  Thrips 
  

  

  The 
  pear 
  thrips 
  causes 
  more 
  in- 
  

   jury 
  to 
  prune 
  trees 
  in 
  the 
  Pacific 
  

   Northwest 
  than 
  to 
  pears 
  or 
  other 
  

   fruits. 
  The 
  insect 
  occurs 
  in 
  west- 
  

  

  Figure 
  46. 
  — 
  Prune 
  twig 
  showing 
  de- 
  

   formed 
  leaves 
  and 
  poor 
  set 
  of 
  fruit 
  

   caused 
  by 
  the 
  pear 
  thrips. 
  

  

  ern 
  and 
  northeastern 
  Oregon, 
  in 
  

   southeastern 
  Washington, 
  and 
  in 
  

   western 
  British 
  Columbia. 
  Ap- 
  

   parently 
  it 
  has 
  been 
  introduced 
  

   from 
  Europe. 
  There 
  are 
  three 
  

   types 
  of 
  injury. 
  The 
  most 
  serious 
  

   injury 
  is 
  that 
  caused 
  by 
  the 
  adult 
  

   thrips, 
  which 
  emerge 
  from 
  the 
  

   ground 
  in 
  the 
  spring, 
  feed 
  in 
  the 
  

   developing 
  buds, 
  and 
  cause 
  de- 
  

   formed 
  leaves 
  and 
  blossoms 
  (fig. 
  

   46), 
  and 
  thus 
  a 
  reduction 
  of 
  the 
  

   crop. 
  Later 
  the 
  adults 
  lay 
  eggs 
  in 
  

   the 
  stems 
  of 
  the 
  fruit 
  and 
  foliage. 
  

   Both 
  the 
  young 
  and 
  the 
  adults 
  

   feed 
  by 
  rasping 
  the 
  surface 
  and 
  

   then 
  sucking 
  out 
  the 
  plant 
  juices. 
  

  

  LIFE 
  history 
  

  

  There 
  is 
  only 
  one 
  generation 
  of 
  

   the 
  pear 
  thrips 
  annually. 
  The 
  

   adults 
  are 
  less 
  than 
  one-twentieth 
  

   inch 
  long, 
  and 
  slim 
  and 
  dark 
  

   brown. 
  They 
  emerge 
  when 
  the 
  

   fruit 
  buds 
  are 
  swelling 
  and 
  be- 
  

   ginning 
  to 
  show 
  green. 
  After 
  

   feeding 
  for 
  about 
  3 
  weeks 
  they 
  

   begin 
  egg 
  laying, 
  which 
  lasts 
  an- 
  

   other 
  3 
  weeks. 
  The 
  eggs 
  are 
  very 
  

   small, 
  whitish, 
  and 
  kidney-shaped, 
  

   and 
  they 
  hatch 
  in 
  less 
  than 
  2 
  

   weeks. 
  The 
  young 
  are 
  white 
  and 
  

   similar 
  to 
  the 
  adults 
  in 
  shape 
  (fig. 
  

   47). 
  They 
  develop 
  for 
  about 
  3 
  

   weeks, 
  then 
  drop 
  to 
  the 
  ground, 
  

   burrow 
  into 
  the 
  soil, 
  and 
  construct 
  

   small 
  cells 
  a 
  few 
  inches 
  to 
  3 
  feet 
  

   from 
  the 
  surface. 
  Here 
  they 
  re- 
  

   main 
  dormant, 
  changing 
  late 
  in 
  

   the 
  fall 
  to 
  adults, 
  which 
  emerge 
  

   the 
  following 
  spring. 
  The 
  pear 
  

   thrips 
  is 
  thus 
  active 
  on 
  the 
  trees 
  

   for 
  only 
  about 
  2 
  months 
  in 
  spring 
  

   and 
  is 
  dormant 
  in 
  the 
  ground 
  the 
  

   rest 
  of 
  the 
  year. 
  

  

  CONTROL 
  

  

  The 
  pear 
  thrips 
  may 
  be 
  con- 
  

   trolled 
  by 
  thoroughly 
  spraying 
  

   the 
  trees 
  during 
  the 
  first 
  warm 
  

   weather 
  after 
  the 
  buds 
  have 
  begun 
  

   to 
  show 
  green. 
  Additional 
  sprays 
  

   may 
  be 
  needed 
  when 
  the 
  blossom 
  

  

  