Hartwig, J.

Sikora, R.A.

Horizon / Pleins textes

Mode-of-action of the carbarnate nematicides cloethocarb, 
aldicarb and carbofuran on Heteroderu schachtii. 
1. Contact activity 
Jiirgen HARTWIG~ and Richard A. SIKORA 
Institut fi? Wamenkranklteiten, Universitat Bonn, Nussallee 9, 5300 Bonn 1, Gennany. 
StTMh.IARY 
The non-systemic  contact  mode-of-action  of  the  systemic  carbarnate  nematicides  cloethocarb  (Lancé@),  aldicdrb (TemikS) and 
carbofuran  (Curaterr 0 )  on Heterodera schvchtii was studied  in  the  laboratory, The nematicides  suppressed  hatch  at  concentrations 
higher than would occtlr under practical field condiüons. Juvenile mobility was, in general, inhibited at concentrations fmm 
5-10 ppm.  Carbofurari  also idiibited juvenile  mobility  at 1 ppm  and  aldicarb at 0.1 ppm.  Orientation  and  penetration  into roots 
was  not affected by  carbamate  concentrations of 0.0001-0.1 ppm. The results  suggest that reduction  of  juvenile  mobility i s  the  main 
factor  responsible- for carbamate  activity  against H. schachtii. Cloethocarb  showed the sarne  activity  rnechanisms  as  aldicarb  and 
carbofuran. 
&SUME 
Modé d’action sur Heterodera  schachtii de  nématicides ù buse  de  carbamcites : 
cbéthocarbè, aldicarbe et carbofuran. 1. Action de contact 
Le mode  d’action  sur Heterodera schachtii de  nématicides  de  contact  non  systémiques à base  de  carbamates - cloéthocarbe 
(Lance@),  aldicarbk (Temik@)  et  carbofuran  (Curaterre@.) - a  été  étudié au laboratoire,  Ces  nématicides  inhibent  I’éclosion à 
des  concentrations  plus  élevées que celles  existant  dans  les  conditions du champ. La mobilité  des  juvéniles  est, en général,  inhibée 
à des  concentrations  de 5 à 10 pprn. Le  carbofuran  inhibe  cette  mobilité  des  juvéniles à un taux  de 1 ppm  et  l’aldicarbe à un taux 
de 0,1 ppm.  L’orientation  des  juvéniles  et  leur  pénétration  dans  les  racines  ne  sont  pas  modifiées  par  des  concentrations  de 0,0001
à 0,l ppm. Ces résultats suggkrent que le principal facteur responsable de l’actiuri des carbamates contre H. schpchtii est la 
diminution  de  la  mobilité  des  juvéniles.  Le  cloéthocarbe  fait  montre  des  mêmes  mécanismes  d’activité  que  l’aldicarbe  et  le  furadan. 
Carbamate insecticides/nematicides are  commonly 
used  plant  protection  components in sugarbeet  produc- 
tion worldwide. They have been  shown to  be effective in 
reducing early root  infection of sugarbeet seedlings by 
Heterodera schachtii usually  resulting  in  significant  in- 
creases in yield. 
A new active ingredient  cloethocarb  has  been shown 
to  be active against  nematodes  (Harries et al., 1980) and 
has a lower mammalian toxicity level than other  carba- 
mate  n maticides. Nothing is known  about  its 
mode-of-action. In this  study  a  comparative analysis was 
made of the contact  mode-of-action of cloethocarb 
(Lance@),  aldicarb  (Temikm)  and carbofuran (Cura- 
te r ro)  towards H. schachtii on sugarbeet. 
Materials  and  methods 
Carbamate  solbtions were produced by grinding  the 
compounds, which are highly water  soluble, in  mortars 
and  dissolving the powder in  tap water  on  a  stirrer for 
12 h at 22 “C. The solubility of these compounds in 
water is : carbofuran - 700 mg/l, aldicarb - 6000 mg& 
cloethocarb - 700 mgIl. The non-water  soluble  granulate 
carriers were then removed by filtration. 
HATCH 
Dilution series of the primary carbamate solutions 
were  prepared  using tap water. The final  concentration 
with  aldicarb was 0.00006 ppm,  with  carbofuran 
* Present  address : Bayer AG, Development Insecticides, Pjlanzenschutzzentrum  Monheim, 5090 Leverkusen,  Gemzany. 
Revue  Nématoi. 14 (4) : 525-530 (199i) 525 
J. Hartwig di R. A. Sikora 
0.007 ppm  and cloethocarb 0.017 ppm. The control was 
prepared with water. 7.5 ml of each  dilution was placed 
in a  test  tube  and 1000 H. schachtii eggs were added to 
each  test  tube. In order  to  prevent  evaporation, the  test 
tubes were covered with aluminium foi1 and  incubated 
in darkness at 23 & 2 O C .  
The eggs and J2 in 1 ml were counted  7 days after 
inoculation. The ratio of eggs with unhatched 52 to 
hatched J2 was determined. The  sum of the egg and 
juvenile counts was at  least 100 for each  counting. The 
number of eggs with  underdeveloped  contents was not 
significant to justify  their  determination in counts. 
The effects of the carbamates on hatch rate was 
determined  using the  formula of Clarke and Shepherd 
(1964) : 
hatch rate = hatch % (carbarnate) loo hatch % (control) 
JWENILE MOBILITY 
The effects of the carbamates on J2 mobility were 
determined using the " direct photography " method 
(Kunz & Klingler, 1976). H. schachtii 52 in water were 
added  to  solutions of cloethocarb,  aldicarb and carbofu- 
ran, so that 10, 5, 1 and 0.1 ppm solutions were produ- 
ced that  had a  nematode  density of 100 J2lml. Tap water 
was used  in  the  control. 
At fiied intervals, from 0.5 to 100 h  after the begin- 
ning of the test,  a 10 ml  nematode  suspension was taken 
from  each  carbamate  solution and immediately  adjusted 
to a  density of ca 1 J2 per pl; 20 pl was then pipetted  into 
the center of a Petri  dish  containing 3 O/O water  agar. The 
surface water on the dishes was evaporated prior to 
inoculation under a laminar flow hood. The actual 
number of juveniles transferred was determined  under 
the microscope. 
After  the 20 pl drap had  evaporated (Ca. 10 min.) the 
J2 moved  randomly  on the surface of the agar, leaving 
behind typical tracks  (Rode & Staar, 1961; Rode, 1970). 
The track  patterns in  the Petri  dishes were recorded at 
periods  from 0.5 to 100 h  using << direct  photography D. 
The negative was enlarged 10 times with the aid of a slide 
projector  ont0 the sensor  plate of a " MOB Kontron, 
AM 3 " planimeter (Fig. 1). The length of the tracks 
was determined by tracing them with the planimeter 
curser Pen. The average distance  travelled  per juvenile 
was calculated  based  on the  length of al1 tracks in  the 
replicate dishes. Juvenile  mobility for each  time  period 
was studied using five replicates and its mean was 
calculated in percent mobility relative to control. 
ORIENTATION A D PENETRATION 
The tests were performed  using  a  modified " sand- 
block method " (Kerstan & Ropke, 1977). A layer of 
chemically pure  sand  (grain size 0.1-0.3 mm)  in a block 
shape of 5 cm length, 2.5 cm  width and 0.5 cm height 
7 
SLIDE  PROJECTOR 
PROJECTED TRACK 
PLANIMETER 
/ SENSOR PLATE 
Fig. 1. Àpparatus  with  slide  projector  used to project  black  and 
white  negatives  of  nematode  tracks  produced  on  an  agar  plate 
ont0 a planimeter for measurement of nematode mobility 
under  the  influence of nematicides. 
was placed in  Petri  dishes (14 cm diameter).  Reference 
lines on  the base of the  Petri dishes were used to mark 
off five Sand-block sectors (Fig. 2). 
A single sugarbeet  plant,  in  the  emerging  second leaf 
pair stage, was inserted in sector 5 and 2000 H. schachtii 
juveniles were pipetted  ont0  sector 1. The entire  sand- 
block was saturated  with  solutions of cloethocarb, aldi- 
carb  or  carbofuran  at  concentrations of  0.1,  0.01, 0.001 
or 0.0001 ppm. The sand-blocks in the control were 
SUGAR  BEET 
NEMATODE 
INOCULATION 
,5cm 
-1 5cm 
SECTION 
Fig. 2. Sand-block  orientation  chamber for testing  the  orienta- 
tion  and  penetration of Heterodera schachtii juveniles. 
526 Revue Nématol. 14 (4) : 525-530 (1991) 
Carbamate  nematicides on Heterodera  schachtii. 1. 
saturated  with water. An additional  control was prepared 
without  sugarbeets. The Petri  dishes were sealed in  order 
to  protect  them against  evaporation. 
After 6 days at 20 & 1 "C in a climatically controlled 
chamber, the sand of each  sector was placed  individually 
in a test  tube, mived with 10 ml tap water and shaken 
vigorously. After the Sand fraction had settled  out, the 
nematodes were counted. In addition to  the  number of 
juveniles in each  sector, the  number of those  penetrated 
into  the  roots was determined by root  staining. 
Results 
HATCH 
The saturated solution of cloethocarb (1700 ppm) 
suppressed  hatch  almost  completely  (Fig. 3). The sup- 
pressive  effect  decreased with decreasing  concentration 
of the active ingredient. Carbofuran did not reduce 
hatch as effectively even in  the  saturated solution. 
Carbofuran  suppressed  hatch  significantly  when  compa- 
red  to  the control d o m  to a concentration of 70 ppm, 
Aldicarb strongly suppressed hatch at concentrations 
between 60 and 6000 ppm  and even 6 ppm  suppressed 
Table 1 
Distribution (%) of Heterodera schachtii J2  in  sectors of the 
sand-block  orientation  chamber  (n = 6). 
Treatment Sector . XZ 
1 2 3 4 5  
CONTROL 
no  plant 48.3  17.2 8.4 10.1  15.5 a 
wirh plant 11.7  2. 0.6  0.9 84.6 b 
CONTROL 
CLOETHOCARB 
0.1  ppm 9.8 1.2 1.1 0.6 87.3 b 
0.01 ppm 16.8 6.3 3.2 2.0 71.9 b 
0.001 ppm 17.5 2.1 1.2 0.7 78.4 b 
0.0001 ppm 18.5 1.7 0.5 1.1 78.9 b 
0.1  ppm 9.9 1.7 0.7 0.6 87.0 b 
0.01  ppm 16.9 1.6 1.0 0.9 79.5 b 
0.001 ppm 10.6 1.5 0.8 0.7 86.4 b 
0.0001 ppm 15.2 2.0 2.2 1.9 78.6 b 
0:l  ppm 11.5 2.7 1.2 0.8 83.7 b 
0.01 ppm 11.6 2.3 1.0 1.3 83.8  b 
0.001  ppm 14.7 2.6 1.0 1.3 80.3 b 
0.0001 ppm 16.8 4.5 1.4 1.5 75.7 b 
ALDICARB 
CARBOFURAN 
1 Distributions  with  t e  same  l tters  are  not  significantly 
different following the Xz-test. 
Revue Nématol. 14 (4) : 525-530 (1991) 
HATCH RATE ALDICARB 
120 
1 O0 
80 
60 
40 
20 
O 
600 60 6 0,6 0,06 0,006 0,0006 0,00006 
PPm 
HATCH  RATE  CARBOFURAN 
f 
'20 1 
1 O0 
80 
60 
40 
20 
700  70 7 0,7  0,07  0,007 
PPm 
HATCH RATE CLOETHOCARB 
120 1 
100 - 
80 - 
60 - 
. 1 AB 
0 ,  
1700  170 17 1,7 0,17 0,017 
w m  
Fig. 3. Effect of  aldicarb  (top),  carbofuran  (center) and cloe- 
thocarb  (bottom)  on  the  hatch  rate of Heterodera schachtii as 
a  function of carbamate  concentration : function  curves 
calculated  from  the  data  points (A); c = significantly 
different  from  the  control  (100 "O) (mean of ten  repetitions). 
527 
J. Hartwig & R. A. Sikora 
% MOBILIV ALDICARB , 
200 p 2 I 
0,s 1 2 3 4 5 6 7 8 9 1 0  20 30 40 50  10
TlME (h) 
% MOBILW, CARBOÇUPAN 
0,5 1 2 3 4 5 6 7 8 9 1 0  20 30 40 50 100 
TIME (h) 
% MOBILQ CLOrmOCARB 
0,i I ' . 8 
d,5 1 2 3 4 5 6 7 8 9 10 20 30 40 56 100 
TlME (h) 
- A 1Oppm - Sppm --- I lppm ........... + 0,lppm 
Fig. 4. Effect of aldicarb  (top),  carbofuran  (center)  and  cloe- 
thocarb  (bottom)  on  juvenile  mobility  as a  function of  time and 
carbahte concentration; e = signifïcantly different from 
the  control  (100 YO mobility)  (mean of five  repetitions). 
528 
hatch.  Contrary to the acuvity curve  for  cioethocarb and 
carbofuran, aldicarb at low concehtrations stimulated 
hatching. 
Table  2 
Heterodera  schachtii root  penettation  rates of  52 in  sector  5 of 
the sand-block ofientation chamber under the influence of 
carbamates (n = 6). 
PPm 0.1 0.01 0.001 0.0001 O 
Control  with  plant - - - - 54.1 
Cloethocarb 65.2 47.3 56.8 54.6 - 
Aldicarb 86.4 48.8 69.9 82.5 - 
Carbofuran 90.5 80.4 75.8 53.1 - 
Mean  values  are  not  different  from  one  another  according  to 
Duncan's  multiple  range  test  at P 5 0.05, 
JWENILE MOBILITY 
Partial inhibition of juvenile mobility occurred at 
concentrations of 5 and  10  ppm cloethocarb with nearly 
total  inhibition  after  20 h at 10 ppm (Fig. 4). Treatment 
levels  of 1 and 0.1 ppm stimulated  mobility. At a 
concentration of 1 ppm, mobility increased  significantly 
147 O/oj 209 O/o and  123 O/o after 0.5, 1 and 6.5 h, respect- 
ively. At 0.1 ppm a signifïcant  stimulatory  effect  took 
place after 4 and 8 h (123 O/O and 11 1 "0). A stable 
inhibitory effect on mobility was not observed at the 
lower concentrations. 
Immobilization of the J2 by aldicarb occurred at a 
concentfation of  10, 5 and 1 ppm after 6, 25 and 50 h, 
respectively (Fig. 4). Mobility was reduced 87 O/o at a 
concentration of O. 1 ppm compared  to the control  after 
100 h. As with cloethocarb, aldicarb also stimulated 
juvenile mobility. After 0.5 h at 5 ppm and after 9 h at 
0.1 ppm, an increase in mobility was measured. This 
increase was 79 9'0 and 29 "O, respectively, over that of the 
control. 
10  and 5 ppm  carbofuran inhibited J2 mobility  after 
22 and  51 h, respectively (Fig. 4). At a concentration of 
1 ppm,  carbofuran  had a mobility-inhibiting  effect 
which reached a maximum of 28.7 O/o lower than  the 
control  value. As with cloethocarb and aldicarb,  mobility 
increases were also observed with  carbofuran.  At 
concentrations of 1 ppm, carbofwan stimulated mobil- 
ity after 0.5 h by 23 %, after 1 h by 48 9'0 and after 
3 h by 33 O/O compared to the control. Mobility was 
increased by 27 O/O at a Concentration of 0.1 ppm and a 
time of 31 h. 
Revue Nérnatol. 14 (4) : 525-530 (1991) 
Carbamate nematicides on Heterodera  schachtii. 1. 
ORIENTATION AND PENETRATION 
In  the absence of a  host  plant, 48.3 YO of the  untreated 
juveniles remained in sector 1 and a significantly lower 
percentage of juveniles was found  in each of sectors 2-5 
(Table 1). When a  sugarbeet was present, 84.6 O/O of all 
untreated J2 migrated  into  sector 5. 
The application of cloethocarb,  aldicarb  and  carbofu- 
ran  did  not  significantly  affect the distribution of the 
juveniles in  the sectors  compared  with  the  distribution 
achieved for  the  untreated juveniles. Thus, carbarnates 
at concentrations from 0.0001-0.1 ppm did  not adversely 
affect JZ orientation. 
There were no  significant  differences between treat- 
ments in  the invasion rates of those juveniles that  had 
reached  sector 5 (Table 2). Neither  the  type of carba- 
mate nor  the concentration of the active  ingredient  had 
qny effect on penetration of juveniles into the root 
system. 
Discussion 
Water  soluble  carbamate insecticides/nematicides c m  
influence both juvenile activity as well as unhatched 
juveniles in encysted eggs. Hatch rate determines the 
maximum number of infective juveniles that can pene- 
trate  a host. An alteration in  hatch behaviour  induced by 
the  action of a  carbamate  compound,  therefore,  directly 
affects the intensity of infection. For this reason, the 
determination of the in vitre hatch behaviour is an 
important  criterion in estimating the effectiveness of a 
carbamate  nematicide  (Kampfe, 1971). 
In Our investigations, cloethocarb,  aldicarb  and  carbo- 
furan inhibited H. schachtii hatch. The intensity of 
inhibition was correlated with concentration. Aldicarb 
inhibited of hatch at very low concentrations when 
compared to cloethocarb and carbofuran. Similar levels 
of hatch  inhibition have been  detected at concentrations 
of 5 ppm (Steudel, 1972; Hough & Thomason, 1975; 
Steele & Hodges,  1975; Steele, 1977). Nevertheless, 
hatch  inhibition  detected  here is  of minor  importance in 
nematode  control due to the nematicide  concentration 
normally attained in  the field. 
Juvenile mobility was studied on water agar using 
orientation  tracks  produced on  the agar  surface  (Rode 
& Staar, 1961; Sandstedt, Sullivan & Schuster, 1961; 
Kunz & Klingler, 1976) whose length are an exact 
measure of mobility. Al1 three  carbamates  had  a  negative 
influence on mobility. Similar  effects were obsenred by 
other workers with  carbamates on H. schachtii(Hough & 
Thomason, 1975; Batterby, 1979). This mode-of-action 
is of practical importance because the concentrations 
required for inhibition are reached in the field at rec- 
ommended rates. The fact that a stimulatory effect 
exists at lower concentrations  indicates  that  the activiq 
of these  carbamates  occurs in two  stages : a  stimulatory 
and an inhibitory  phase. 
Revue Néinatol. 14 (4) : 525-530 (1991) 
Because of their cholinesterase inhibiting activity, 
carbamates may disrupt juvenile orientation and host 
recognition. Disruption in orientation  and host recognit- 
ion, however, are of minimal  importance  at  concentrat- 
ions  where juvenile mobility is inhibited.  Therefore, the 
influence of the carbamates on orientation was tested at 
concentrations that  did  not alter  mobility.  Orientation of 
the juveniles was not altered by the  three  carbamates at 
concentrations of 0.0001-0.1 ppm.  Juvenile  attraction to 
the sugarbeet  seedlings was not impaired.  Furthermore, 
these concentrations did not affect root penetration. 
Reductions in Pratylenchus  penetrans and Meleidogyne 
incegnita penetration after treatment with 10-25 ppm 
carbofuran, however, have been r.eported (Di Sanzo, 
1973). 
Our results  demonstrate  that he H. schachtiiinfection 
process on sugarbeet is negatively influenced by clo- 
ethocarb,  aldicarb and carbofuran. The reduction 
of juvenile mobility is the  most  important  component of 
the mode-of-action responsible for limiting early root 
infection. 
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A - -  
Accepté  pour publication le 7 septembre 1990. 
530 Revue Nématol. 14 (4) : 525-530 (1991) 


Mode-of-action of the carbamate nematicides cloethocarb, aldicarb and carbofuran on Heterodera schachtii : 1. Contact activity

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