﻿SMALL 
  MOTH-BORERS 
  OF 
  SUGAR 
  CANE 
  IN 
  BRITISH 
  GUIANA. 
  

  

  461 
  

  

  When 
  the 
  " 
  old 
  bank 
  " 
  has 
  reached 
  this 
  height, 
  if 
  the 
  stools 
  are 
  not 
  required 
  

   for 
  " 
  stumps,"* 
  they 
  are 
  weeded 
  down 
  and 
  thrown 
  on 
  the 
  " 
  trash 
  bank,"* 
  only 
  to 
  

   be 
  a 
  further 
  danger 
  to 
  the 
  tops. 
  The 
  borers 
  they 
  harbour, 
  having 
  their 
  food 
  supply 
  

   thus 
  suddenly 
  cut 
  off, 
  either 
  pupate, 
  if 
  they 
  are 
  far 
  enough 
  developed 
  to 
  do 
  so, 
  or 
  

   leave 
  the 
  shoot, 
  and 
  in 
  their 
  search 
  for 
  food 
  enter 
  the 
  tops. 
  It 
  these 
  trash 
  banks 
  

   be 
  examined 
  a 
  few 
  days 
  after 
  they 
  have 
  been 
  weeded, 
  they 
  will 
  be 
  found 
  to 
  contain 
  

   many 
  such 
  larvae, 
  and 
  as 
  many 
  as 
  12 
  full-grown 
  larvae, 
  in 
  a 
  prepupal 
  stage, 
  have 
  

   been 
  found 
  in 
  one 
  of 
  these 
  banks 
  (a 
  distance 
  of 
  37 
  feet), 
  while 
  small 
  larvae 
  can 
  be 
  found 
  

   trying 
  to 
  bore 
  into 
  pieces 
  of 
  hard 
  cane 
  about 
  the 
  trash 
  bank. 
  

  

  It 
  is 
  the 
  general 
  practice, 
  whenever 
  possible, 
  to 
  fork 
  both 
  banks 
  in 
  plant 
  fields. 
  

   Under 
  the 
  present 
  system 
  the 
  new 
  rows 
  are 
  forked 
  and 
  planted 
  with 
  tops, 
  and 
  after 
  

   a 
  period 
  varying 
  from 
  one 
  to 
  several 
  weeks 
  one 
  of 
  the 
  old 
  banks 
  is 
  forked, 
  the 
  old 
  

   stools 
  being 
  turned 
  under. 
  The 
  trash, 
  which 
  up 
  to 
  that 
  time 
  has 
  been 
  on 
  the 
  other 
  

   old 
  row, 
  is 
  now 
  transferred 
  to 
  the 
  forked 
  bank, 
  the 
  process 
  being 
  known 
  as 
  " 
  changing 
  

   banks." 
  A 
  further 
  period 
  then 
  elapses, 
  varying 
  also 
  to 
  several 
  weeks, 
  before 
  the 
  

   second 
  bank 
  is 
  forked. 
  During 
  the 
  interval 
  the 
  remaining 
  old 
  stools 
  spring 
  to 
  about 
  

   three 
  feet 
  again, 
  and, 
  as 
  before, 
  harbour 
  borers. 
  

  

  Table 
  II 
  gives 
  the 
  results 
  of 
  examinations 
  of 
  three 
  such 
  fields, 
  and 
  shows 
  this 
  

   early 
  infestation 
  from 
  the 
  old 
  banks. 
  The 
  first 
  examination 
  was 
  made 
  when 
  the 
  

   rows 
  were 
  about 
  12 
  inches 
  high, 
  the 
  old 
  bank 
  at 
  the 
  time 
  being 
  two 
  or 
  three 
  feet 
  

   high, 
  and 
  in 
  most 
  instances 
  was 
  then 
  undergoing 
  weeding 
  to 
  allow 
  the 
  tops 
  a 
  chance. 
  

   The 
  second 
  examination 
  was 
  made 
  about 
  a 
  month 
  later 
  when 
  the 
  rows 
  were 
  about 
  

   18 
  inches 
  high, 
  the 
  old 
  banks 
  being 
  then 
  about 
  the 
  same 
  height. 
  

  

  TABLE 
  II. 
  

  

  Examination 
  of 
  Plant 
  Fields 
  showing 
  Infestation 
  of 
  Rows 
  from 
  Old 
  Banks. 
  

  

  

  Percentage 
  of 
  

  

  

  Percentage 
  of 
  

  

  

  Field. 
  

  

  shoots 
  infested 
  

  

  Treatment 
  

  

  shoots 
  infested 
  

  

  Difference 
  

  

  1st 
  Examination. 
  

  

  of 
  

  

  2nd 
  Examination. 
  

  

  of 
  

  

  

  i 
  

  

  Field. 
  

  

  

  Infestation. 
  

  

  

  Row. 
  

  

  Old 
  Bank. 
  

  

  Row. 
  

  

  Old 
  Bank. 
  

  

  No. 
  1 
  

  

  4-9 
  

  

  No 
  O.B., 
  weeded 
  

   down. 
  

  

  One 
  Bank 
  forked 
  

  

  already. 
  

  

  4-7 
  

  

  •• 
  

  

  Nil 
  

  

  No. 
  2 
  

  

  Nil. 
  

  

  10-8 
  per 
  cent. 
  

   O.B. 
  just 
  being 
  

   weeded. 
  

  

  One 
  bank 
  forked 
  

  

  6-8 
  

  

  One 
  O.B. 
  re- 
  

   maining 
  18 
  

   inches 
  high. 
  

   Infestation 
  

   heavy 
  ; 
  not 
  

   estimated. 
  

  

  Increase, 
  6-8 
  

  

  No. 
  3 
  

  

  2-7 
  

  

  7-7 
  per 
  cent. 
  

   Both 
  O.B. 
  

   present. 
  

  

  One 
  bank 
  forked 
  

   about 
  12 
  days 
  

   before 
  2nd 
  

   exam. 
  Both 
  

   O.B. 
  weeded. 
  

  

  9-3 
  

  

  One 
  O.B. 
  re- 
  

   maining 
  18 
  

   inches 
  high. 
  

   Infestation 
  

   heavy 
  ; 
  not 
  

   estimated, 
  but 
  

   gang 
  working 
  

   this 
  field, 
  got 
  

   most 
  borers 
  

   from 
  O. 
  B. 
  

   See 
  figures 
  

   below. 
  

  

  Increase 
  6-6 
  

  

  * 
  See 
  Appendix. 
  

  

  