MINISTERE DE L'ENSZXNEMENT SUPERIEUR JtlJ DE LA...
MINISTERE DE L'ENSZXNEMENT SUPERIEUR
JtlJ DE LA RECHERCHE SCIENTIFIQUE
MINISTERE DU DEVELOPP= RURAL
SECRETARIAT D'ETAT A LA RECHEROHE
SCIENTIFIQUE ET TECHNIQUE
WRRENT STATUS OF ENTOMOLOGICAL STUDIES ON CASSAVA IN SENEGAL,
LIKELY FUTURE D~ZXELOFMXNTS AND SUGGw$TED CQLLABORATI%!3
.fXE%ARCHANDDEWLORtfENTALNEED8'
V.S. Bhatnagar, 14. Ndoye and G. Pierrasd
CILSS/FAO IPM PROJECT, B.P. 51
BANBEY,S3WXL
Novembre 1982
INSTITUT SENEGALAIS DE RFXXERCm AG:RICOI;ES
((I.S.R.A*)
PROJET CILSS LUTTE INTEGREE
OOl!@OSANTE NATIONALE DU SENEGAL
@JRRJ&t?T STATUS OF ZXTOXOLOGICAL STUDIES ON C&%AVA IN SE;N%=J,
T,,,IKEL~ FUTURF, DI~WKWEBTS *h-ND SUGGESTED COWORATI~
R"E%,RCH AND DEXELOPMENT1L NEEDS '
V.S. Bhatnagar, 1J, Ndoye and G. Pierrard
CJLSS/FAO IPM P-OJET, B.P. 51
BJEBEX, SENEERL
1, INTRODUCTION
In Senegal, cassava was considered to be a most eoonamic, low risk
and important subsdstenoe trop for small and marginal farnm% in varied
rainfall areas-low (rainfall - 300 to 500 mm p distributed during three
months in regions of Louga and Thies), medium (rainfall-500 to 800 mm 1
distributed during four months in regions of Diourbel and Sin~?-fd.OUd
and high (rainfall - 800 to 1000 mm ; distributed during five months in
region of Casamance). Until a few years ago it was frequenty oonsidered
that cassava is generally free from insects and other pests in Senegal.
AS a result and also due to the subsistence nature of this trop i$
received a limited attention from the ~tomologis~~s, With the appearmce
of cassava mealy bug (considered to be Phenacocus manihati Mat, Ferr,)
the production in Senegal has oonsiderably reduced (Anonymous, 19&),
Rowever, the farmers continue to grow this trop with little or no pest
management technology.
Presented in "'Workshop on Biological Control and Resistanoe
Breeding to Control the cassava mealybug (Phene;ocus manihoti)
and Green Spider kIite (Mononychellus tyajoa) in Afric;a".
6-10 December 1982, International Institute of Tropical
Agriculture, Ibadsn, Nigeria (West bfrioa)l.
II. CTJRRENT STX'US OF XN'TOL~~OLOGICAL STUDIXS IN SENEGAL
The occurence of cassava maalybug in Senegal was first remrded in
region of Sine-Saloum, southern part s of Louga and western parts of
region of Diourbel in October 1977. It is believed that mealyb\\lg infested
plant material was accidently introduced in Senegal from elsewhere in mid
seventies, Subsequently the infestation spread in regions of Thies and
Casamance. As a result, the national production which was estimated to
be 75 111 tons in 1978 (Xinistère du Développement Rural, 1978) bas been
considerably reduced. Though no systematic surveys on loss estimates
have been made in Sanegal, it is believed that in some farmers fields
the losses caused by mealybugs are to the extent of 50.0-90.0 per cent.
In the region of Thies the production in 1978 was rtssessed to 'be 5c? 000
tons (68.0 per cent of the national production). Due to the mealybug
devastations the current production levels are les:; than 10 000 tons
(J.Y. Durand - persona1 communication).
Limited studias using various pre-planting insecticidal treatments
to the planting material have been attempted in Senegal. Some insectici-
dal treatments resulted into phytotoxicity (Bill Settle, US4ID Entomo-
logist, Dakar - persona1 communication).
Keeping in view the economio importance and subsistence nature of
this trop and due to the economic trop losses caussd by mealybugs on
cassava, a preliminary survey was initiated in Senegal in January 1982
in order to establish the range of insect species present withi a parti-
cular emphasis on the status of the mealybugs and its natural para.sites/
predators/pathogens present, Besides this preliminary survey, the ento-
mologiests of the CIL,%/FlsO IF% Project in Senegal establishedl contacts
with the local authorities to understand the status of mealybugs on
cassava, The current situation in Senegal is summarised below,
1, By far the most important pest on cassava in Senegal is mealy-
bug. The exact identity of mealybugs in Senegal is however still
WlkllOWL
2. In low rainfall areas of regions of Louga and Thies the incidence
of mealybugs was higher in some fields along the Niay& 5cm
(North sea toast).
3. In the higher rainfall areas of region of Casamance severe
damage to cassava occurs in fields near the G,unbia river and
in low Ian& of Casamace. In post-rainy season the mealybug
infestation spreads east ward.
3
4. Infestation levels have been higher in region of Thies than in
the region of Sine-Saloum, A very high incidence of mealybugs
was observed in some fiel& in region of Thies - upto 8Ei.O per
cent plants attacked in April 1982.
Usually older plants carried a higher menlybug infestation
e,g, in Febuary a 18 month old trop was severely infested (70.0
per cent). By end of April the corresponding figures rose to
80.0 and 25,O per cent, respeotively. This was in contrast to
the situation in fields in the region of Sine-Saloum (Sokone,
Gossas and Nioro-du-Rip), where either very little (5.0 per
cent plants attacked) or no infestation of mealybugs was observed
during January - Kay 1982. A partial and subsequent defoliation
occurred in several plants with heavy inf'estations in March -
April in region of Thies. This resulted ::into drying of P:lant
tissues and obviously me& loss of planting material and loss
in yield, The defoliated plants usually formed new buds lthich
were soon badly attacked.
5. In region of Thies the mealybug populations and the infestation
build up during post rainy season9 particularly during Febuary-
April when the population builds up very rapidly, By end Nay -
eerly June it reaches to'self - destructive' phase.
6. Samples of cassava plant material with mealybug infestations
collected from region of Thies during Febuary - April have
yielded two hymenopteran (Encyrtidae), one coccinelid and a
spider species, No estimates on parasitism or predation levels
were made in these preliminary surveys. Howerer, the levels
appears to be very lad. The identificatio;n of these parasites/
predators is awaited.
II;E,LIKELY FUTURE DEVELOF%ENTS AND SUGGESTED COLLABORQTIVE
RZSEARCH AND DEVELOF'I@XTAL NZXDS 2
Preliminary surveys have, to serre extent, helped to clarify the
status of mealybugs on cassava in only a limited cassava growing seras
in Senegal. Future surveys on status of native parasites/predators/l
pathogens is obviously important.
2 The views expressed are those of authors only 2nd does not
necessarily represent those of CILSS, ISRA and/or FAO.
4
It is essential that surveys in different eco1og:ica.l and rainfall areas
are immediately intensified since ecological studies, including those on
identity and past/‘Parasitoid relationships are crucially import:ant in
understanding the pest related constraints and to pin point the reason
as to why this pest has been SO severe on cassava in Senegal,
The surveys ni.11 have to be extended not on.Ly to different ecolo-
gical and rainfall zones but also in important cassava based trop systems
since cassava is often intercropped with cereals and legumes in Senegal.
Sole trop fields are needed to regularly monitor tlifferences in status
of mealybugs and its natural enemies, if they exi:;t and compariso:ns
made with inter - and/or nixed çrop situations. Subsequently, possibili-
ties of utilising the native and/or other exotic :,arasites/predators/
pathogens in future ‘on-farm CIBC/IITA/CILSS/FAO
collaborative biologi-
cal control/pest management pro ject * at two or three different “bot -
spot’ locations needs to be explored. Being a long season trop cassava
is perhaps ideally suited for biological programme in Senegal,
Various cultural practices both in existing (traditional) and
proposed (improved.) cassava based trop systema and cassava cultivars
are major factors in bath mealybug and its parasite build up ,and will
need attention and. investigations. Subsequently, studies relating to
effects of already known and recommended control measures in la package,
especially the ef’fects of recommended or rosis-tance cultivars, reoommen-
ded pre-planting insecticidal treatments, and/or releases of exotic
natural enemies in a collaborative project wïL1 be vital for the formu-
lation of future integrated pest management program on cassava. Il?31
Project in Senegal will be in a position to participate in a rnulti -
location exotic parasite species for different rainfall areas Will be
needed for such evaluations. The suggested work needs to be initiated
in collaboration with national coordinated researc,h (IsRA)*
and develop-
mental (SODEVB and SO&ïIVAC)* agencies,
There is a specific need for a much Gloser c:ollaboration with the
scientists and agents engaged in production oriented research and exten-
tion work on cassava in Senegal for a realistic mu:Lti-disciplinaq
research, survey and developmental approach to rea:Lise the economic,
simple and practical solutions acceptable to the f’srmers. Thare are no
sko2-t cuts.
* ISRA
- Institut Sénégalais de Recherches Agricoles.
SODEVA
- Sociét6 do Développement et de Vulgarisation Agric:ole,
SOLINAC
- SociétB de Hise en Valeur Agricole de la Casamance,
5
IV. REmCE
dnonymous. 1981. Synthèse des travaux effectués en protection des
végétaux slu Sé&gsl, Projet Lutte Intégrée,
Composante Nationale du Sén<sgalP Bambay, St'inégal,
Jcaxwier 1981, ppD 55.
Dur,znd, J. Y,, 1982. Persona1 communication.
Ministère du D6veloppemen.t Rural. 1978. Rapport annuel
Direction Gënérnle de la Production A@icole,
République du S&E@, 1977 - 1978, ppe 201.
Settle, B. 1982, Persona1 communication,
JtlJ DE LA RECHERCHE SCIENTIFIQUE
MINISTERE DU DEVELOPP= RURAL
SECRETARIAT D'ETAT A LA RECHEROHE
SCIENTIFIQUE ET TECHNIQUE
WRRENT STATUS OF ENTOMOLOGICAL STUDIES ON CASSAVA IN SENEGAL,
LIKELY FUTURE D~ZXELOFMXNTS AND SUGGw$TED CQLLABORATI%!3
.fXE%ARCHANDDEWLORtfENTALNEED8'
V.S. Bhatnagar, 14. Ndoye and G. Pierrasd
CILSS/FAO IPM PROJECT, B.P. 51
BANBEY,S3WXL
Novembre 1982
INSTITUT SENEGALAIS DE RFXXERCm AG:RICOI;ES
((I.S.R.A*)
PROJET CILSS LUTTE INTEGREE
OOl!@OSANTE NATIONALE DU SENEGAL
@JRRJ&t?T STATUS OF ZXTOXOLOGICAL STUDIES ON C&%AVA IN SE;N%=J,
T,,,IKEL~ FUTURF, DI~WKWEBTS *h-ND SUGGESTED COWORATI~
R"E%,RCH AND DEXELOPMENT1L NEEDS '
V.S. Bhatnagar, 1J, Ndoye and G. Pierrard
CJLSS/FAO IPM P-OJET, B.P. 51
BJEBEX, SENEERL
1, INTRODUCTION
In Senegal, cassava was considered to be a most eoonamic, low risk
and important subsdstenoe trop for small and marginal farnm% in varied
rainfall areas-low (rainfall - 300 to 500 mm p distributed during three
months in regions of Louga and Thies), medium (rainfall-500 to 800 mm 1
distributed during four months in regions of Diourbel and Sin~?-fd.OUd
and high (rainfall - 800 to 1000 mm ; distributed during five months in
region of Casamance). Until a few years ago it was frequenty oonsidered
that cassava is generally free from insects and other pests in Senegal.
AS a result and also due to the subsistence nature of this trop i$
received a limited attention from the ~tomologis~~s, With the appearmce
of cassava mealy bug (considered to be Phenacocus manihati Mat, Ferr,)
the production in Senegal has oonsiderably reduced (Anonymous, 19&),
Rowever, the farmers continue to grow this trop with little or no pest
management technology.
Presented in "'Workshop on Biological Control and Resistanoe
Breeding to Control the cassava mealybug (Phene;ocus manihoti)
and Green Spider kIite (Mononychellus tyajoa) in Afric;a".
6-10 December 1982, International Institute of Tropical
Agriculture, Ibadsn, Nigeria (West bfrioa)l.
II. CTJRRENT STX'US OF XN'TOL~~OLOGICAL STUDIXS IN SENEGAL
The occurence of cassava maalybug in Senegal was first remrded in
region of Sine-Saloum, southern part s of Louga and western parts of
region of Diourbel in October 1977. It is believed that mealyb\\lg infested
plant material was accidently introduced in Senegal from elsewhere in mid
seventies, Subsequently the infestation spread in regions of Thies and
Casamance. As a result, the national production which was estimated to
be 75 111 tons in 1978 (Xinistère du Développement Rural, 1978) bas been
considerably reduced. Though no systematic surveys on loss estimates
have been made in Sanegal, it is believed that in some farmers fields
the losses caused by mealybugs are to the extent of 50.0-90.0 per cent.
In the region of Thies the production in 1978 was rtssessed to 'be 5c? 000
tons (68.0 per cent of the national production). Due to the mealybug
devastations the current production levels are les:; than 10 000 tons
(J.Y. Durand - persona1 communication).
Limited studias using various pre-planting insecticidal treatments
to the planting material have been attempted in Senegal. Some insectici-
dal treatments resulted into phytotoxicity (Bill Settle, US4ID Entomo-
logist, Dakar - persona1 communication).
Keeping in view the economio importance and subsistence nature of
this trop and due to the economic trop losses caussd by mealybugs on
cassava, a preliminary survey was initiated in Senegal in January 1982
in order to establish the range of insect species present withi a parti-
cular emphasis on the status of the mealybugs and its natural para.sites/
predators/pathogens present, Besides this preliminary survey, the ento-
mologiests of the CIL,%/FlsO IF% Project in Senegal establishedl contacts
with the local authorities to understand the status of mealybugs on
cassava, The current situation in Senegal is summarised below,
1, By far the most important pest on cassava in Senegal is mealy-
bug. The exact identity of mealybugs in Senegal is however still
WlkllOWL
2. In low rainfall areas of regions of Louga and Thies the incidence
of mealybugs was higher in some fields along the Niay& 5cm
(North sea toast).
3. In the higher rainfall areas of region of Casamance severe
damage to cassava occurs in fields near the G,unbia river and
in low Ian& of Casamace. In post-rainy season the mealybug
infestation spreads east ward.
3
4. Infestation levels have been higher in region of Thies than in
the region of Sine-Saloum, A very high incidence of mealybugs
was observed in some fiel& in region of Thies - upto 8Ei.O per
cent plants attacked in April 1982.
Usually older plants carried a higher menlybug infestation
e,g, in Febuary a 18 month old trop was severely infested (70.0
per cent). By end of April the corresponding figures rose to
80.0 and 25,O per cent, respeotively. This was in contrast to
the situation in fields in the region of Sine-Saloum (Sokone,
Gossas and Nioro-du-Rip), where either very little (5.0 per
cent plants attacked) or no infestation of mealybugs was observed
during January - Kay 1982. A partial and subsequent defoliation
occurred in several plants with heavy inf'estations in March -
April in region of Thies. This resulted ::into drying of P:lant
tissues and obviously me& loss of planting material and loss
in yield, The defoliated plants usually formed new buds lthich
were soon badly attacked.
5. In region of Thies the mealybug populations and the infestation
build up during post rainy season9 particularly during Febuary-
April when the population builds up very rapidly, By end Nay -
eerly June it reaches to'self - destructive' phase.
6. Samples of cassava plant material with mealybug infestations
collected from region of Thies during Febuary - April have
yielded two hymenopteran (Encyrtidae), one coccinelid and a
spider species, No estimates on parasitism or predation levels
were made in these preliminary surveys. Howerer, the levels
appears to be very lad. The identificatio;n of these parasites/
predators is awaited.
II;E,LIKELY FUTURE DEVELOF%ENTS AND SUGGESTED COLLABORQTIVE
RZSEARCH AND DEVELOF'I@XTAL NZXDS 2
Preliminary surveys have, to serre extent, helped to clarify the
status of mealybugs on cassava in only a limited cassava growing seras
in Senegal. Future surveys on status of native parasites/predators/l
pathogens is obviously important.
2 The views expressed are those of authors only 2nd does not
necessarily represent those of CILSS, ISRA and/or FAO.
4
It is essential that surveys in different eco1og:ica.l and rainfall areas
are immediately intensified since ecological studies, including those on
identity and past/‘Parasitoid relationships are crucially import:ant in
understanding the pest related constraints and to pin point the reason
as to why this pest has been SO severe on cassava in Senegal,
The surveys ni.11 have to be extended not on.Ly to different ecolo-
gical and rainfall zones but also in important cassava based trop systems
since cassava is often intercropped with cereals and legumes in Senegal.
Sole trop fields are needed to regularly monitor tlifferences in status
of mealybugs and its natural enemies, if they exi:;t and compariso:ns
made with inter - and/or nixed çrop situations. Subsequently, possibili-
ties of utilising the native and/or other exotic :,arasites/predators/
pathogens in future ‘on-farm CIBC/IITA/CILSS/FAO
collaborative biologi-
cal control/pest management pro ject * at two or three different “bot -
spot’ locations needs to be explored. Being a long season trop cassava
is perhaps ideally suited for biological programme in Senegal,
Various cultural practices both in existing (traditional) and
proposed (improved.) cassava based trop systema and cassava cultivars
are major factors in bath mealybug and its parasite build up ,and will
need attention and. investigations. Subsequently, studies relating to
effects of already known and recommended control measures in la package,
especially the ef’fects of recommended or rosis-tance cultivars, reoommen-
ded pre-planting insecticidal treatments, and/or releases of exotic
natural enemies in a collaborative project wïL1 be vital for the formu-
lation of future integrated pest management program on cassava. Il?31
Project in Senegal will be in a position to participate in a rnulti -
location exotic parasite species for different rainfall areas Will be
needed for such evaluations. The suggested work needs to be initiated
in collaboration with national coordinated researc,h (IsRA)*
and develop-
mental (SODEVB and SO&ïIVAC)* agencies,
There is a specific need for a much Gloser c:ollaboration with the
scientists and agents engaged in production oriented research and exten-
tion work on cassava in Senegal for a realistic mu:Lti-disciplinaq
research, survey and developmental approach to rea:Lise the economic,
simple and practical solutions acceptable to the f’srmers. Thare are no
sko2-t cuts.
* ISRA
- Institut Sénégalais de Recherches Agricoles.
SODEVA
- Sociét6 do Développement et de Vulgarisation Agric:ole,
SOLINAC
- SociétB de Hise en Valeur Agricole de la Casamance,
5
IV. REmCE
dnonymous. 1981. Synthèse des travaux effectués en protection des
végétaux slu Sé&gsl, Projet Lutte Intégrée,
Composante Nationale du Sén<sgalP Bambay, St'inégal,
Jcaxwier 1981, ppD 55.
Dur,znd, J. Y,, 1982. Persona1 communication.
Ministère du D6veloppemen.t Rural. 1978. Rapport annuel
Direction Gënérnle de la Production A@icole,
République du S&E@, 1977 - 1978, ppe 201.
Settle, B. 1982, Persona1 communication,