October  29,  1896. 
JOURNAL  HORTICULTURE  AND  COTTAGE  GARDENER. 
42^ 
CUCUMBER  AND  TOMATO  EELWORM. 
There  is  a  division  in  the  animal  kingdom  known  to  the  zoologist 
as  vermes  (worms).  This  division  comprises  a  number  of  diverse  groups, 
one  of  which  is  known  by  the  name  of  nematoidea  (S'?'.,  ntma,  thread  ; 
eidot,  form).  The  nematodes  are,  therefore,  threadworms,  of  which 
more  than  a  thousand  species  are  known. 
Daring  the  last  few  years  many  Cucumber  and  Tomato  growers  in 
this  country  have  lost  a  considerable  number  of  their  plants  annually 
owing  to  the  formation  of  nodular  enlargements  (root  galls)  upon  the 
roots.  For  some  time  the  cause  of  tSese  nodular  formations  was  a 
mystery  to  growers,  and  not  until  Miss  Ormerod  issued  a  report  upon 
the  subject  (Report  of  Observations  of  Injurious  Insects,  &c. ;  1892, 
pages  127-137)  did  it  become  generally  known  that  the  formation  of 
galls  on  the  roots  of  Tomatoes,  Cucumbers,  and  a  few  other  plants 
groViag  under 
glass  was  the 
work  of  a  ne¬ 
matode  worm 
called  by  Mul¬ 
ler  Heterodera 
radicicola. 
The  destruc¬ 
tiveness  of  this 
pest  is  so  great 
as  to  often 
cause  the 
grower  to  lose 
from  60  to  75 
per  cent,  of  the 
above  named 
plants,  and, 
therefore,  one 
cannot  wonder 
that  they  dread 
its  introduc¬ 
tion  into  their 
establishments. 
Cncum  her 
plants  fall  a 
more  easy  prey 
than  Tomatoes 
to  an  attack  of 
root  eelworm. 
This  is  no  doubt 
owing  to  the 
soft  nature  of 
the  tissues  of 
the  first  named 
plants,  for  I 
have  seen  in 
several  i  n- 
stances  Tomato 
plants  growing 
and)  fruiting 
fairly  well  in 
houses  so  in¬ 
fested  as  to 
make  it  impos¬ 
sible  to  grow 
Cucumbers. 
The  roots  of 
plants  when  in¬ 
fested  with  root 
eelworm  pre¬ 
sent  an  irregu¬ 
lar,  knotty,  or 
warty  appear¬ 
ance,  and  are 
often  from  two 
to  ten  times 
larger  in  diam¬ 
eter  than  ordi- 
nary  roots. 
These  nodular 
enlargements 
or  root  galls 
when  first 
formed  are 
smooth  and  light  in  colour,  but  at  a  later  date  the  surface  roughens 
and  cracks,  and  is  then  dark  brown,  owing  to  the  root  gall  having 
commenced  to  decay. 
If  we  take  one  of  these  brown  decaying  galls  and  pull  it  carefully 
apart,  we  may  probably  see  with  the  naked  eye  small  white  oval 
bodies  lying  in  the  darkened  decaying  tissues.  These  more  or  less  oval 
bodies  are  the  matured  female  cysts  (fig.  1),  being  from  one-fiftieth  to 
one-hundredth  of  an  inch  in  diameter.  They  are  pointed  at  the  head 
end,  and  under  the  microscope  the  cyst  or  chamber  looks  like  an  inflated 
bladder,  or  what  Professor  Atkinson  calls  “  a  crooked-necked  squash.” 
In  the  head  end  we  find  a  mouth  (fig.  1,  A),  provided  with  a  hollow 
exsertile  spear  (fig.  2).  This  spear  is  found  in  both  sexes,  and  can  be 
extended  with  considerable  force,  its  use  being  (1)  to  batter  in  the 
cell  walls  of  the  plant,  either  to  enter  or  exit ;  and  (2)  to  form  a  passage 
by  which  the  food  may  be  drawn  into  the  stomach  of  the  worm.  The 
food  passage  looks,  when  viewed  under  the  microscope,  like  a  dark  line 
running  down  the  centre  of  the  spear,  which  terminates  in  an  egg- 
shaped  muscular  gizzard  or  stomach  (fig.  1,  B)  ;  the  latter  being  attached 
to  the  alimentary  canal. 
If  we  look  carefully  at  one  of  these  female  cysts  under  the  micro¬ 
scope  we  may  be  able  to  see  lying  in  its  interior  two  long  coiled 
cylindrical  objects  having  free  ends  (fig.  1).  These  are  the  genital 
tubes,  and  in  a  fully  developed  cyst  will  be  found  to  be  packed  with 
eggs  in  all  stages  of  development.  The  eggs  are  developed  in  immense 
numbers  in  the  ovaries  (fig.  1,  (7),  and  as  they  increase  in  size  they  pass 
along  the  oviduct  (fig.  1,  B)  and  are  finally  expelled  from  the  vulva 
(fig.  1,  E).  When  the  eggs  are  expelled  they  are  cylindrical  in  shape, 
but  they  soon  change  in  form,  ultimately^becoming  bean  shaped  (fig.  3). 
The  leggs  are 
from  three  to 
4  -  thousandth 
part  of  an  inch 
in  diameter. 
The  eggs  are 
filled  with  pro- 
t  o  p  1  a  8  m,  in 
which  may  be 
found  a  nu¬ 
cleus  (fig.  3,A) 
The  early  pro¬ 
cess  of  develop¬ 
ment  of  the 
egg  into  an  em¬ 
bryonic  worm 
is  similar  to 
that  of  a  living 
cell  in  the 
growing  part 
of  a  plant — i  e  , 
the  nucleus 
and  protoplas¬ 
mic  contents 
divide,  a  cell 
wall  is  formed 
in  the  division, 
so  that  the 
mother  cell  or 
egg  (fig.  3,  A) 
now  contains 
two  daughter 
cells  (fig.  3,2f). 
By  similar  di¬ 
visions  these 
daughter  cells 
again  divide 
(fig.  3,  C,  B), 
until  a  mass  of 
cellular  tissue 
is  formed  (fig. 
4,  A),  from 
which  the 
young  embry¬ 
onic  eelworm 
is  ultimately 
developed  (fig. 
4,  B,  C,  B). 
The  embryo  re¬ 
mains  for about 
two  days  in 
the  egg  and 
then  comes  out 
(fig.  6). 
The  young 
wormlet  is 
about  the 
12 -thousandth 
part  of  an  inch 
in  diameter, 
and  is  thread¬ 
like  in  shape, 
tapering  grad¬ 
ually  to  a  blunt 
head-end.  and  gently  into  a  slender  needle-like  tail.  This  is  known  as 
the  larval  stage.  During  the  larval  stage  male  and  female  are  both  alike  in 
appearance — i.e.,  eel-shaped,  and  are  easily  mistaken  for  Tylenchus 
devastatrix  (the  stem  eelworm). 
When  the  eelworm  leaves  the  egg  it  generally  finds  itself  imprisoned 
within  one  of  the  cells  of  the  plant.  As  soon  as  the  supply  of  food  in 
the  cell  is  exhausted  the  worm  has  either  to  pass  out  of  the  cell  or  die 
of  starvation.  It  can,  however,  pass  from  cell  to  cell  by  battering  in  the 
cell  wall,  which  it  does  by  means  of  the  spear. 
Sometimes  hundreds  of  worms  are  liberated  by  the  decay  of  the 
root  gall  ;  these  find  a  fresh  portion  of  root,  and  enter  it  by  piercing 
through  the  cell  walls.  The  plant  is  not  able  to  expel  the  intruder, 
but  it  tries  to  repair  the  injury  by  the  development  of  fresh  cells,  hence 
Fia.  76.— HETERODERA  RADICICOLA.  (Jlighlg  magnified.') 
Eeferenees: — Fig.  1,  Female  oyst :  — (o)  mouth,  (ft)  stomach,  (c)  ovaries,  (d)  oviducts,  (e)  vulva.  Pig.?,  Exsertile  spear. 
Fig.  3,  Eggs  in  various  stages  of  development;  (n)  nucleus.  Pig.  4,  Development  of  embryo.  Fig.  6,  Worm  (larval  stage) 
emerging  from  egg.  Pig.  6,  Commencement  of  change  from  larval  to  cystic  stage.  Fig.  7,  More  advanced  development 
of  male.  Pig.  8,  Female  from  larval  to  cystic  stage. 
