﻿47 
  

  

  been 
  disinfected. 
  A 
  fungus 
  disease 
  was 
  keeping 
  down 
  the 
  Coccid, 
  the 
  

   aggregated 
  insects 
  being 
  reduced 
  to 
  a 
  sort 
  of 
  pulp. 
  For 
  disinfecting 
  the 
  

   cuttings 
  kerosine 
  mixture 
  has 
  been 
  suggested. 
  For 
  this 
  mixture, 
  

   to 
  25 
  grams 
  of 
  soap 
  disolved 
  in 
  500 
  c.c. 
  boihng 
  water, 
  add 
  2 
  htres 
  

   petroleum, 
  gradually 
  stirring 
  the 
  while; 
  add 
  to 
  600 
  c.c. 
  of 
  this 
  emul- 
  

   sion, 
  400 
  c.c. 
  of 
  Phenyl, 
  or 
  300 
  c.c. 
  of 
  Creolin. 
  This 
  mixture 
  at 
  a 
  

   strength 
  of 
  1 
  per 
  cent, 
  in 
  water 
  damages 
  green 
  leaves, 
  and 
  should 
  

   only 
  be 
  employed 
  for 
  disinfecting 
  the 
  soil 
  or 
  against 
  scale 
  insects 
  

   attacking 
  the 
  bark. 
  

  

  Hardenberg 
  (C. 
  B.). 
  Peach-tree 
  Aphides. 
  — 
  Agric. 
  Jl. 
  Union 
  S. 
  Africa, 
  

   Pretoria, 
  vi, 
  no. 
  2, 
  Aug. 
  1913, 
  pp. 
  224-235. 
  

  

  During 
  the 
  winter 
  and 
  early 
  spring 
  of 
  1912, 
  the 
  author 
  made 
  some 
  

   observations 
  and 
  experiments 
  regarding 
  the 
  life-history 
  and 
  control 
  

   of 
  the 
  black 
  and 
  green 
  peach 
  aphids 
  [Aphis 
  persicae, 
  Boyer, 
  and 
  Rhopa- 
  

   losiphum 
  dianthi, 
  Schr.] 
  in 
  the 
  Pretoria 
  and 
  Johannesburg 
  districts, 
  

   where 
  the 
  two 
  insects 
  are 
  generally 
  very 
  prevalent, 
  and 
  may 
  cause 
  a 
  

   complete 
  failure 
  of 
  the 
  peach 
  crop 
  in 
  some 
  localities. 
  The 
  observa- 
  

   tions 
  can 
  be 
  divided 
  into 
  such 
  as 
  relate 
  to 
  (a) 
  life-history, 
  including 
  

   hibernation 
  and 
  dispersal 
  ; 
  (b) 
  parasitism 
  ; 
  and 
  (c) 
  the 
  use 
  of 
  tobacco 
  

   extract 
  as 
  a 
  means 
  of 
  control. 
  

  

  The 
  following 
  summary 
  is 
  given 
  of 
  the 
  results 
  of 
  the 
  experiments 
  : 
  — 
  - 
  

   (1) 
  In 
  sheltered 
  situations 
  the 
  black 
  peach 
  aphis 
  probably 
  hiber- 
  

   nates 
  on 
  the 
  trees, 
  and 
  may 
  breed 
  through 
  the 
  winter 
  ; 
  (2) 
  though 
  

   primarily 
  infesting 
  the 
  young 
  shoots 
  and 
  jruit-buds, 
  the 
  black 
  aphis 
  

   will 
  also 
  attack 
  the 
  leaves 
  ; 
  (3) 
  dispersal 
  takes 
  place 
  most 
  probably 
  

   through 
  the 
  agency 
  of 
  winged 
  individuals, 
  which 
  are 
  produced 
  as 
  soon 
  

   as 
  a 
  favourable 
  mean 
  temperature 
  is 
  reached 
  ; 
  the 
  distribution 
  is 
  too 
  

   scattered 
  to 
  admit 
  of 
  its 
  being 
  effected 
  by 
  ants 
  carrying 
  the 
  young 
  

   aphides 
  to 
  other 
  situations 
  on 
  the 
  tree 
  ; 
  (4) 
  the 
  presence 
  of 
  aphis 
  at 
  

   the 
  base 
  of 
  the 
  flower-bud 
  causes 
  it 
  to 
  swell 
  and 
  open 
  prematurely, 
  or 
  

   at 
  least 
  in 
  advance 
  of 
  others 
  which 
  are 
  not 
  attacked 
  by 
  aphides 
  ; 
  

   (5) 
  the 
  green 
  peach 
  aphis 
  breeds 
  in 
  the 
  winter 
  on 
  cabbage, 
  parsnips, 
  

   and 
  probably 
  other 
  cruciferous 
  plants 
  ; 
  (6) 
  in 
  the 
  absence 
  of 
  definite 
  

   data 
  regarding 
  the 
  season 
  history 
  of 
  the 
  black 
  aphis 
  parasite, 
  we 
  may 
  

   presume 
  that 
  the 
  hibernating 
  colonies 
  keep 
  this 
  parasite 
  breeding 
  

   through 
  the 
  winter 
  season 
  ; 
  (7) 
  the 
  black 
  peach 
  aphis 
  is 
  attacked 
  by 
  

   one 
  hymenopterous 
  internal 
  parasite 
  and 
  preyed 
  upon 
  by 
  two 
  species 
  

   of 
  Syrphid 
  flies 
  and 
  three 
  species 
  of 
  lady-birds 
  ; 
  (8) 
  the 
  total 
  length 
  

   of 
  the 
  life-cycle 
  of 
  the 
  Syrphid, 
  Xanthogramma 
  scutellaris, 
  is 
  about 
  

   three 
  weeks 
  ; 
  egg 
  stage, 
  three 
  to 
  four 
  days, 
  larval 
  stage 
  about 
  twelve 
  

   days, 
  and 
  pupal 
  stage 
  five 
  days 
  ; 
  (9) 
  the 
  Syrphid 
  pairs 
  in 
  late 
  afternoon 
  ; 
  

   eggs 
  are 
  deposited 
  at 
  intervals 
  of 
  about 
  one 
  minute 
  ; 
  (10) 
  tobacco 
  

   extract 
  in 
  a 
  solution 
  containing 
  about 
  0*082 
  per 
  cent 
  nicotin 
  is 
  the 
  

   most 
  effective 
  strength 
  ; 
  no 
  advantage 
  is 
  gained 
  by 
  using 
  a 
  stronger 
  

   solution 
  ; 
  this 
  kills 
  the 
  aphis 
  within 
  24 
  hours, 
  being 
  equivalent 
  to 
  a 
  

   dilution 
  of 
  "Eagle 
  Brand" 
  extract 
  of 
  1:100, 
  and 
  of 
  "Lion 
  Brand" 
  

   extract 
  1:80 
  ; 
  (11) 
  the 
  tobacco 
  wash 
  is 
  more 
  efiective 
  in 
  sunshine 
  

   than 
  in 
  dull 
  cloudy 
  weather 
  ; 
  (12) 
  green 
  peach 
  aphis 
  can 
  be 
  effectively 
  

   kept 
  under 
  control 
  by 
  three 
  thorough 
  sprayings 
  about 
  five 
  days 
  apart, 
  

   the 
  first 
  being 
  applied 
  as 
  soon 
  as 
  the 
  first 
  leaves 
  open 
  out 
  ; 
  the 
  first 
  

   appearance 
  of 
  the 
  aphis 
  should 
  be 
  watched 
  for 
  closely 
  ; 
  (13) 
  for 
  effec- 
  

   tive 
  spraying 
  an 
  underspray 
  attachment 
  is 
  essential 
  ; 
  the 
  spray 
  should 
  

  

  