﻿28 
  

  

  CIRCULAR 
  2 
  70, 
  U. 
  S. 
  DEPARTMENT 
  OF 
  AGRICULTURE 
  

  

  by 
  fire. 
  This 
  should 
  not 
  be 
  al- 
  

   lowed 
  to 
  happen 
  to 
  valuable 
  trees, 
  

   as 
  the 
  reduction 
  in 
  the 
  leaf 
  surface 
  

   seriously 
  interferes 
  with 
  the 
  

   growth 
  of 
  the 
  fruit 
  and 
  the 
  devel- 
  

   opment 
  of 
  fruit 
  buds. 
  This 
  insect 
  

   is 
  widely 
  distributed 
  in 
  the 
  United 
  

   States, 
  having 
  come 
  in 
  from 
  

   Europe. 
  

  

  Figure 
  34. 
  — 
  Pear-slug 
  and 
  its 
  injury 
  to 
  a 
  

   leaf. 
  Enlarged. 
  

  

  LIFE 
  HISTORY 
  

  

  The 
  adults 
  are 
  glossy 
  black, 
  

   four-winged 
  flies, 
  about 
  one-fifth 
  

   inch 
  long. 
  They 
  are 
  known 
  as 
  

   sawflies 
  because 
  they 
  cut 
  slits 
  in 
  

   the 
  upper 
  surface 
  of 
  the 
  leaves, 
  in 
  

   which 
  the 
  eggs 
  are 
  laid. 
  The 
  eggs 
  

   in 
  the 
  leaves 
  look 
  like 
  small 
  blis- 
  

   ters. 
  The 
  young 
  slugs 
  hatch 
  in 
  

   a 
  week 
  or 
  two 
  and 
  feed 
  almost 
  alto- 
  

   gether 
  on 
  the 
  upper 
  surface, 
  

   usually 
  avoiding 
  any 
  leaves 
  that 
  

   may 
  have 
  been 
  attacked 
  by 
  aphids 
  

  

  or 
  blister 
  mites. 
  Just 
  after 
  molt- 
  

   ing 
  the 
  slugs 
  are 
  yellow, 
  but 
  they 
  

   soon 
  secrete 
  a 
  slime 
  which 
  gives 
  

   them 
  the 
  characteristic 
  olive 
  green 
  

   or 
  black 
  color. 
  Their 
  bodies 
  are 
  

   somewhat 
  enlarged 
  in 
  front 
  and 
  

   taper 
  behind. 
  The 
  slugs 
  complete 
  

   their 
  growth 
  in 
  less 
  than 
  a 
  month, 
  

   drop 
  to 
  the 
  ground, 
  and 
  form 
  cells 
  

   in 
  the 
  soil, 
  within 
  which 
  they 
  

   transform 
  to 
  adults 
  in 
  a 
  couple 
  of 
  

   weeks. 
  The 
  second 
  brood 
  of 
  slugs 
  

   appears 
  on 
  the 
  trees 
  in 
  August, 
  

   and 
  these, 
  when 
  full-grown, 
  spend 
  

   the 
  winter 
  in 
  earthen 
  cells 
  from 
  

   which 
  the 
  adult 
  sawflies 
  emerge 
  

   the 
  following 
  spring. 
  

  

  CONTROL 
  

  

  The 
  pear-slug 
  is 
  easily 
  con- 
  

   trolled 
  and 
  does 
  not 
  become 
  a 
  pest 
  

   if 
  arsenicals 
  are 
  used 
  on 
  pear 
  

   trees 
  in 
  the 
  spring 
  for 
  other 
  in- 
  

   sects. 
  If 
  the 
  slug 
  is 
  the 
  only 
  in- 
  

   sect 
  present, 
  a 
  spray 
  containing 
  

   lead 
  arsenate 
  in 
  the 
  proportion 
  of 
  

   2 
  pounds 
  to 
  100 
  gallons 
  of 
  water 
  

   is 
  very 
  effective, 
  or 
  lead 
  arsenate 
  

   or 
  hydrated 
  lime 
  may 
  be 
  used 
  as 
  

   a 
  dust. 
  If 
  it 
  is 
  necessary 
  to 
  spray 
  

   for 
  the 
  second 
  brood 
  in 
  August, 
  

   and 
  the 
  fruit 
  is 
  still 
  on 
  the 
  trees, 
  

   a 
  nicotine 
  spray 
  should 
  be 
  used. 
  

   This 
  spray 
  should 
  contain 
  three- 
  

   fourths 
  of 
  a 
  pint 
  of 
  nicotine 
  sul- 
  

   fate 
  plus 
  2 
  or 
  3 
  pounds 
  of 
  soap 
  in 
  

   solution 
  to 
  100 
  gallons 
  of 
  water. 
  

   If 
  the 
  fruit 
  has 
  been 
  harvested 
  

   the 
  lead 
  arsenate 
  spray 
  may 
  be 
  

   used. 
  (See 
  Cautions, 
  p. 
  60.) 
  

  

  Pear 
  Leaf 
  Worm 
  

  

  Holes 
  one-fourth 
  inch 
  or 
  more 
  

   in 
  diameter 
  are 
  sometimes 
  found 
  

   in 
  pear 
  leaves 
  late 
  in 
  April 
  or 
  in 
  

   May. 
  A 
  close 
  examination 
  will 
  

   usually 
  show 
  a 
  green 
  worm 
  

   stretched 
  along 
  the 
  edge 
  of 
  each 
  

   hole, 
  feeding 
  on 
  the 
  leaf 
  (fig. 
  35). 
  

   This 
  is 
  a 
  pear 
  leaf 
  worm, 
  which 
  

   occurs 
  throughout 
  the 
  Pacific 
  

   Northwest 
  and 
  in 
  California. 
  

  

  