The role of wild grasses on densities of lepidopteran stemborer pests along altitudinal gradient in Kenya

Full text

This article was downloaded by: [IRD Documentation]
On: 08 September 2014, At: 21:58
Publisher: Taylor & Francis
Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer
House, 37-41 Mortimer Street, London W1T 3JH, UK
Annales de la Société entomologique de France
(N.S.): International Journal of Entomology
Publication details, including instructions for authors and subscription information:
http://www.tandfonline.com/loi/tase20
The role of wild host plants in the abundance of
lepidopteran stem borers along altitudinal gradient
in Kenya
George O. Ong’amo a , Bruno P. Le Rü a , Stéphane Dupas b , Pascal Moyal b , Eric
Muchugu c , Paul-André Calatayud a & Jean-François Silvain b
a Noctuid Stem Borer Biodiversity Project (NSBB) , Institut de Recherche pour le
Développement / International Centre of Insect Physiology and Ecology (IRD/ICIPE) ,
Nairobi , P O Box 30772 , Kenya
b IRD, UR R072 c/o CNRS, UPR 9034, Laboratoire Evolution, Génomes et Spéciation,
avenue de la Terrasse , Gif/Yvette , 91198 , France
c Stem borer Biological Control Project (ICIPE) , Nairobi , P.O. Box 30772 , Kenya
Published online: 31 May 2013.
To cite this article: George O. Ong’amo , Bruno P. Le Rü , Stéphane Dupas , Pascal Moyal , Eric Muchugu , Paul-André
Calatayud & Jean-François Silvain (2006) The role of wild host plants in the abundance of lepidopteran stem borers along
altitudinal gradient in Kenya, Annales de la Société entomologique de France (N.S.): International Journal of Entomology,
42:3-4, 363-370, DOI: 10.1080/00379271.2006.10697468
To link to this article: http://dx.doi.org/10.1080/00379271.2006.10697468
PLEASE SCROLL DOWN FOR ARTICLE
Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained
in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no
representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of
the Content. Any opinions and views expressed in this publication are the opinions and views of the authors,
and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied
upon and should be independently verified with primary sources of information. Taylor and Francis shall
not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other
liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or
arising out of the use of the Content.
This article may be used for research, teaching, and private study purposes. Any substantial or systematic
reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any
form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://
www.tandfonline.com/page/terms-and-conditions

Ann. soc. entomol. Fr. (n.s.), 2006, 42 (3-4) : 363-370
363
ARTICLE
 e role of wild host plants in the abundance of lepidopteran
stem borers along altitudinal gradient in Kenya
Abstract. Presence of wild host plants of stem borers in cereal-growing areas has been considered
as reservoirs of lepidopteran stem borers, responsible for attack of crops during the growing season.
Surveys to catalogue hosts and borers as well as to assess the abundance of the hosts were carried
out during the cropping and non- cropping seasons in different agro-ecological zones along varying
altitude gradient in Kenya. A total of 61 stem borer species belonging to families Noctuidae (25),
Crambidae (14), Pyralidae (9), Tortricidae (11) and Cossidae (2) were recovered from 42 wild plant
species. Two noctuids, Busseola fusca (Fuller), Sesamia calamistis Hampson, and two crambids,
Chilo partellus (Swinhoe) and Chilo orichalcociliellus (Strand) were the four main borer species found
associated with maize plants. In the wild, B. fusca was recovered from a limited number of host plant
species and among them were Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel)
T. D ura nd & Sch inz , Arundo donax L. and Pennisetum purpureum Schumacher. In contrast, the host
range of C. partellus was considerably wider [13 for S. calamistis]. However, the number of larvae of
these species was lower in the wild compared to cultivated fi elds, thus the role of natural habitat as a
reservoir for cereal stem borers requires further studies. Importance of the wild host plants as well as
borer diversity along the altitudinal gradient is discussed.
Résumé. Le rôle des plantes hôtes sauvages dans l’abondance des lépidoptères foreurs de
graminées selon un gradient altitudinal au Kenya. La présence de plantes hôtes sauvages de
foreurs autour des parcelles cultivées a toujours été considérée comme préjudiciable à la production
des céréales dans la mesure où elles constituent des réservoirs pour les foreurs. Des enquêtes ont
été menées au Kenya, pendant et en dehors des périodes culturales, selon un gradient altitudinal, afi n
de déterminer le rôle de ces plantes hôtes sur les populations de ravageurs. Soixante et une espèces
de lépidoptères foreurs appartenant aux familles des Noctuidae (25), Crambidae (14), Pyralidae
(9), Tortricidae (11) et Cossidae (2) ont été récoltées sur 42 plantes hôtes sauvages. Les principales
espèces de foreurs associées au maïs sont Busseola fusca (Fuller) et Sesamia calamistis Hampson
(Noctuidae) et Chilo partellus ( Swinhoe) et Chilo orichalcociliellus (Strand) (Crambidae). Dans les
habitats sauvages, B. fusca a été trouvé sur un nombre restreint de plantes hôtes sauvages telles que
Sorghum arundinaceum (Desvaux) Stapf, Setaria megaphylla (Steudel) T. Durand & Schinz, Arundo
donax L. and Pennisetum purpureum Schumacher. A l`inverse, S. calamistis et C. partellus ont été
trouvées associées à plus de plantes hôtes sauvages [S. calamistis (13) , C. partellus (5)]. Toutefois,
le nombre total de chenilles de ces quatre espèces de ravageur trouvé dans les habitats sauvages
est très inférieur à celui trouvé dans les parcelles cultivées, aussi le rôle des habitats sauvages en
tant que réservoir pour les lépidoptères foreurs de céréales requiert des études plus approfondies.
L`importance de la diversité des lépidoptères foreurs dans les plantes hôtes sauvages en fonction du
gradient altitudinal est discutée.
Keywords: Stem borer, Pennisetum purpureum, Arundo donax, Lepidoptera, Africa.
G O. O’(1), B P. L R(1), S D(2), P M(2), E M(3),
P-A C(1) & J-F S(2)
(1) Noctuid Stem Borer Biodiversity Project (NSBB), Institut de Recherche pour le Développement / International Centre of Insect Physiology and Ecology
(IRD/ICIPE), P. O. Box 30772, Nairobi, Kenya
(2) IRD, UR R072 c/o CNRS, UPR 9034, Laboratoire Evolution, Génomes et Spéciation, avenue de la Terrasse, 91198 Gif/Yvette, France
(3) Stem borer Biological Control Project (ICIPE), P.O. Box 30772, Nairobi, Kenya
E-mail: gongamo@icipe.org, bleru@icipe.org, dupas@legs.cnrs-gif.fr,
moyal@legs.cnrs-gif.fr, emuchugu@icipe.org, pcalatayud@icipe.org,
silvain@legs.cnrs-gif.fr
Accepté le 20 avril 2006
Downloaded by [IRD Documentation] at 21:58 08 September 2014

364
G. O. O’, B. P. L R, S. D, P. M, E. M, P.-A. C & J.-F. S
Lepidopteran stem borers are among the most
important insect pests infesting maize and sorghum
in sub-Saharan Africa (Schulthess et al. 1997; Overholt
et al. 2001; Guofa et al. 2002). In East and Southern
Africa, Chilo partellus (Swinhoe 1884) and Busseola
fusca (Fuller 1901) are the most important species
while Eldana saccharina Walker 1865 and Sesamia
calamistis Hampson 1910 constitute the minor species
(Seshu Reddy 1998; Kfi r 1997). With the exception
of C. partellus, which is native to Asia, the other borer
species are indigenous to Africa and are assumed to
have co-evolved with some native grasses and sedges
(Nye 1960; Polaszek & Khan 1998; Overholt et al.
2001). Understanding the interactions between these
pests and their cultivated and native hosts has been
thought of as a prerequisite for developing sustainable
management strategies (Bowden 1976).
In East and Southern Africa, populations of
Noctuidae and Crambidae often occur as a community
of species with overlapping spatial and temporal
distribution. In Kenya, B. fusca and C. partellus are
the main pests of maize [Zea mays L.] and sorghum
[Sorghum bicolor (L.) Moench] (Ong’amo 2005). While
B. fusca dominates the high altitude areas, C. partellus
is recorded mainly in the lowlands and mid-altitudes
(Seshu Reddy 1983; Overholt et al. 2001; Ong’amo
et al. 2006). Crop residues have been reported as
responsible for re-establishment of pest populations
early in the cropping season (Ingram 1958; Nye 1960).
However, information on the role of wild hosts in
carry-over of pest populations is scanty.
Stem borers occur in large numbers in maize and
sorghum plants during cropping seasons (Songa et al.
1998), and their populations survive in wild hosts or
in crop stubbles as diapausing larvae during crop free
periods (Ingram 1958; Nye 1960; Polaszek & Khan
1998; Haile & Hofsvang 2001). Alternative hosts in
the vicinity of the crop fi elds and crop residues enhance
survival of borers during off -season, and thereby are
responsible for pest attacks on crops in the subsequent
season (Polaszek & Khan 1998). In contrast, oviposition
preference studies showed certain wild grasses to be
highly attractive to ovipositing moths, though larval
survival and adult fecundity are generally low (Haile
& Hofsvang 2002). Based on these interactions,
hypotheses has been created and validated with fi eld
and laboratory trials for S. calamistis and E. Saccharina
(Shanower et al. 1993; Schulthess et al. 1997). Low
borer incidences in maize fi elds in the forest zones
of Cameroon, Ivory Coast and Ghana were partly
attributed to abundant wild grasses in the surrounding
fi elds (Schulthess et al. 1997).  ese views appear to
diff er either because generated hypotheses have not
been fully tested or because of diff erences in borer
species.  is study was initiated to catalogue hosts and
borers in Kenya, and estimates their abundance along
diff erent altitudinal gradients.
Materials and methods
Description of the surveyed gradients
Surveys were made during 2003/2004 cropping and non-
cropping seasons in 31 localities randomly selected in maize
producing areas in Kenya (fi g. 1). Localities were grouped in
three altitudinal gradients [< 1000, 1000-1500 and >1500 m
above sea level (asl)]. Both 1000-1500 and >1500m asl zones
are characterized by extensive maize monocultures producing
about 80% of the crop consumed in Kenya (De Groote 2002).
 e other zone (< 1000 asl) is mainly occupied by subsistence
farmers who produce approximately 20% of the total maize
consumed in the country.
Rainfall in these zones is highly variable and generally bimodal
in distribution.  is allows for two annual cropping seasons,
the fi rst lasting from March - April to May - August (long rainy
growing season) and the second from October to December
(short rainy season). Most farmers regard long rainy season as
the most important season as it is more reliable.
Cultivated host (maize)
Ovipositing noctuids are reported to have a strong preference
for pre-tasseling crops and thus attack plants early in the season.
 ere is one or two stem borer generations during the short rainy
season depending on the crop cycle and the duration of pre-
tasseling unlike during the long rainy season where there are two
generations. Long rainy season populations are thought to either
come from adjacent earlier planted crops or wild habitats.  is
study thus aimed at capturing the fi rst generation of the long
rainy season. Several maize farms within a radius of 400m of each
survey locality were sampled. Visits were made during four to six
weeks after germination of maize during the long rainy season. In
each session, 100 randomly selected maize stems were inspected
for stem borer infestation. Infested stems were cut and dissected
for larval and pupal recovery. Other cultivated graminaceous
crop-hosts such as S. bicolor, Saccharum offi cinarum L., and
Eleusine corocana L. were also sampled. However these hosts were
sampled in very few localities and are presented together with the
wild host plants (tab. 2).
Wild host plants
Surveys in wild host habitats in the vicinity of crop fi elds were
done during both cropping and non-cropping seasons. Since
borer densities on wild hosts plants are considerably lower
than on cultivated cereals (Nye 1960; Schulthess et al. 1997),
selective sampling was adopted to increase the chances of
fi nding borers. In each locality, all potential hosts belonging
to the Poaceae, Cyperaceae and Typhaceae families found
within 200-300 m from the border of cultivated maize fi eld
were carefully examined for symptoms of stem borer damage.
Damaged plants were cut at the bases and dissected for recovery
of larvae and pupae. Plants from which the larvae or pupae
were collected were identifi ed. In cases where identities of the
infested plants were not known, voucher specimens were taken
to the East African herbarium in Nairobi for identifi cation.
Downloaded by [IRD Documentation] at 21:58 08 September 2014

Stem borers abundance in wild and cultivated habitats
365
Figure 1
Map of Kenya outlining localities surveyed for stem borer infestation in both maize and wild hosts during the study.
Downloaded by [IRD Documentation] at 21:58 08 September 2014

366
G. O. O’, B. P. L R, S. D, P. M, E. M, P.-A. C & J.-F. S
Stem borer species
Upon dissection, recovered larvae were individually introduced
into glass vials containing B. fusca diet (Onyango &
Ochieng’Odero 1994) where they remained until pupation or
emergence of natural enemies. Pupae were then individually
transferred to separate plastic vials until adult emergence.
Noctuid moths were shipped to Centre National de la Recherche
Scientifi que, Gif-sur-Yvette Cedex (France) where they were
identifi ed by one of us (Pascal Moyal). Apart from C. partellus
and E. saccharina, identity of the crambids, pyralids, tortricids
and cossids could not be confi rmed and are thus presented in
their tentative families. Specifi c characters used for identifi cation
of Chilo species appear to be very variable (Blezynski 1970)
and more so for species close Chilo orichalcociliellus (Strand,
1911). To avoid risk of misidentifi cation, materials close to
C. orichalcociliellus are presented here as C. orichalcociliellus
group. In addition, presentations of some materials in the text
are limited to genera (Noctuidae family) and super-families
(Pyraloidea, Tortricoidea and Cossoidea).
A correlation test was performed to estimate the relationship
between the relative importance of stem borer species and altitude.
Results
Stem borer abundance in maize fields along the
altitude
Busseola sp nr phaia, Sciomesa piscator Fletcher 1961,
Sesamia nonagrioides botanephaga (Lefebvre 1827) and
Sesamia sp nov 5 were found infesting maize in addition to
B. fusca, C. partellus, S. calamistis and C. orichalcociliellus
group which were the main pest species (tab 1). Pest
species coexisted in most localities with varying densities
along the altitudinal gradient (F2,171 = 8.86; p = 0.0002).
 e highest density (1.39 larvae/plant) was recorded in
mid altitude gradient followed by low altitude gradient
Table 1. Stem borer pests collected among maize plants in diff erent localities along the altitudinal gradient.
In parenthesis along columns are the number of larvae collected among wild host plants; B.f. - B. fusca; S.c.- S. calamistis; C.p. - C. partellus; C.o. group - C.
orichalcociliellus group.
Localities Latitude
Longitude
Altitude
(m asl)
Larvae from cultivated crops
B. f. S. c. C. p. C. o. group
Low altitude (<1000)
Malindi S 03°08.054’ E 40°08.098’ 33 0 112 774(2) 22(12)
Mombasa 6 S 04°19.196’ E 39°32.471’ 43 0 36(32) 295(30) 16(120)
Mombasa 8 S 04°32.502’ E 39°07.831’ 103 0 84(8) 676(6) 4(5)
Shimba 1 S 04°11.463’ E 39°31.921’ 111 1 76 287 75(9)
Bura S 01°02.007’ E 39°53.988’ 148 0 9 357(36) 0
Shimba 2 S 04°08.843’ E 39°26.963’ 417 0 53 456(2) 83(96)
Taita 3 S 03°24.917’ E 38°32.075’ 610 0 1 976(210) 0
Mombasa 7 S 02°40.627’ E 38°11.715’ 739 10 81 487(201) 0(82)
Rift Valley 3 S 01°45.837’ E 36°03.991’ 914 4 17(3) 98(275) 0
Mombasa 3 S 02°21.894’ E 37°53.528’ 989 20 19(3) 387(78) 0(2)
Garissa 2 S 00°55.672’ E 38°05.676’ 994 2 13(3) 520(19) 0(379)
Mid altitude (1000 – 1500)
Rift Valley 6 N 00°35.168’ E 36°00.921’ 1084 22 13(100) 0 0
Kisumu 2 S 00°10.357’ E 34°54.804’ 1143 128 16 1014 0
Mombasa 2 S 02°05.453’ E 37°29.388’ 1153 19 29 1400(372) 0
Kitui1 S 01°24.114’ E 37°48.047’ 1160 2 7 384 0
Mt. Kenya 2 S 00°71.720’ E 37°26.730’ 1179 88 66(23) 1726(494) 1
Taita 2 S 03°26.292’ E 38°21.955’ 1180 81 15 114(4) 0
Homa Bay 1 S 00°40.382’ E 34°32.128’ 1250 101 9 580 0
Kisumu 4 N 00°35.775’ E 34°27.165’ 1283 227 20 484 0
Loitoktok S 02°43.109’ E 37°31.169’ 1331 20 68(2) 278(12) 0
Kitui 2 S 01°19.482’ E 38°03.684’ 1363 106(2) 47(31) 166 0
Garissa 1 S 01°07.185’ E 37°35.879’ 1363 2 65 833 0
High altitude (>1500)
Kakamega N 00°22.530’ E 34°89.660’ 1551 209(87) 3(16) 0 0
Kisii 2 S 00°54.790’ E 34°31.740’ 1583 60 1(9) 16 0
ICIPE S 01°13.209’ E 36°53.775’ 1625 129 26(4) 41 0
Mt. Kenya1 S 00°55.793’ E 37°09.343’ 1639 595 92 639(2) 0
Taita 1 S 03°23.626’ E 38°20.339’ 1729 618 90 1 0
Machakos S 01°29.347’ E 37°16.611’ 1978 707 7 0 0
Kitale 2 N 01°11.738’ E 34°49.106’ 2160 603(47) 1(7) 2 0
Gatamaiyu S 01°00.057’ E 36°43.022’ 2181 297(2) 7 0 0
Kisii 1 S 00°46.216’ E 34°58.788’ 2223 279 3(9) 0 0
Downloaded by [IRD Documentation] at 21:58 08 September 2014

Stem borers abundance in wild and cultivated habitats
367
(0.84 larvae/plant), while the lowest density (0.80
larvae/plant) was recorded in high altitude gradient.
Stem borer community signifi cantly varied along
the altitudinal gradient (F11,112 = 54.62; p < 0.0001).
Distribution of B. fusca was strongly correlated to the
increase in altitude (F1,29 = 25.65; p < 0.001; r2 = 0.42)
with more larvae in high altitude zone (>1500 m) where
it constituted about 85% of the community. A negative
relationship was observed in the proportion of both
S. calamistis (F1,29 = 4.80; p < 0.05; r2 = 0.14) and C.
orichalcociliellus group (F1,29 = 8.80; p < 0.05; r2 = 0.23)
with an increase in altitude though they constituted
Table 2. Host plants from which diff erent stem borer super-families were recovered.
Family Host plants Noctuoidea Pyraloidea Tortricoidea Cossoidea
Poaceae Arundo donax L. 6200
Cymbopogon nardus (L.) Rendle 25000
Cynodon aethiopicus Clayton & Harlan 103000
Cynodon dactylon (L.) Persoon 13000
Cynodon nlemfuensis Vanderyst var. nlemfuensis 55000
Digitaria milanjiana (Rendle) Stapf 28520
Echinochloa pyramidalis (Lam.) Hitchc. & Chase 178 141 0 7
Eleusine corocana L. 40000
Eriochloa fatmensis (Hochsttetter & Steudel) Clayt. 176000
Eriochloa meyerana (Nees) Pilger 64200
Euclaena mexicana Schrader 0 14 0 0
Hyparrhenia papillides (Hochstetter) Stapf 4400
Hyperthelia dissoluta (Steudel) Clayton 4400
Panicum deustum  unb 55 22 0 0
Panicum maximum Jacquin 1189 547 0 0
Panicum merkeri Mez 37 16 0 0
Panicum porphyrhizos Steudel 31000
Paspalidium geminatum (Forskal) Stapf 29000
Pennisetum macrourum Trinius 41000
Pennisetum purpureum Schumacher 1569 146 0 0
Pennisetum trachyphyllum Pilger 491000
Phragmites mauritianus Kunth 3103
Rottboellia cochinchinensis (Loureiro) Clayton 6 201 0 0
Saccharum offi cinarum L. 49000
Schoenoplectus corymbosus (Roemer & Schultes) 0 0 13 0
Setaria megaphylla (Steudel) T. Durand. & Schinz 742000
Sorghum arundinaceum (Desvaux) Stapf 162 1761 0 0
Sorghum bicolor (L.) Moench 539 2330 0 0
Vossia cuspidata (Roxburg) Griffi th 24000
Zea mays L. 5862 13192 0 0
Cyperaceae Carex chlorosaccus C.B. Clarke 0 14 0 0
Cyperus latifolius Poiret 7 21 0 0
Cyperus maculatus Boeck. 0 0 35 0
Cyperus alopecuroides Rottboll 0 6 20 0
Cyperus articulatus L. 12 0 55 0
Cyperus dereilema Steudel 0 14 0 0
Cyperus dichrostachyus A. Richard 19 37 0 0
Cyperus distans L. 25 18 14 0
Cyperus dives Delile 77 18 10 0
Cyperus exaltatus Retzius 5 29 7 0
Cyperus prolifer Lamark 0 0 24 0
Typhaceae Typha domingensis Persoon 207 38 0 0
Very low number of larvea were recovered from Setaria sphacelata (Schumacher) Moss, Echinochloa haploclada (Stapf) Stapf, Cenchrus ciliaris L., Cyperus
rotundus L. and Cyperus involucratus Rottboll and have thus been excluded from the table.
Downloaded by [IRD Documentation] at 21:58 08 September 2014

368
G. O. O’, B. P. L R, S. D, P. M, E. M, P.-A. C & J.-F. S
the minor proportion of the borer community in low
altitude zone (8 and 3% respectively). Unlike the other
species, frequencies of C. partellus did not vary with
increase in altitude (F1,29 = 3.92; p > 0.05; r2 = 0.12)
though it dominated mid- and low altitude zones
where it constituted 72 and 86% respectively.
Stem borer pests among wild host plants
Stem borer species recovered from maize plants
were also obtained from wild host plants growing in
the vicinity of crop fi elds.  eir abundance varied
among localities along the altitudinal gradient. B. fusca
was recovered only from fi ve localities on four Poaceae
species, namely Setaria megaphylla (Steudel) T. Durand
& Schinz (Kakamega) Arundo donax L. (Mt. Kenya 1),
Sorghum arundinaceum (Desvaux) Stapf. (Kakamega,
Kitui 2 and Kitale 2) and Pennisetum purpureum
Schumacher (Gatamaiyu).  ese localities were situated
in both the mid- (Kakamega and Kitui 2) and high
altitude (Mt. Kenya 1, Kitale 2 and Gatamaiyu) zones.
In contrast, S. calamistis was recovered in 14 localities
from 13 diff erent host plants belonging to Poaceae
(9) and Cyperaceae (4) families (tab. 2). S. calamistis
larvae were recovered mainly from Cyperus distans L.,
Eleusine corocana L., Panicum porphyrhyzos Steudel, S.
arundinaceum, Paspalidium geminatum (Forskol) Stapf
and Vossia cuspidata (Roxburg) Griffi th. However, S.
arundinaceum was found infested in many localities
(Kitale 2, Mombasa 3, Mombasa 6, Mt. Kenya 2 and
Rift valley 3) across all altitudinal gradients.
Like in maize, crambids C. partellus and C.
orichalcociliellus group occurred mainly in low altitude
localities. C. partellus was mainly collected from S.
arundinaceum, P. purpureum, Rottboellia cochinchinensis
(Loureiro) Clayton and Panicum maximum Jacquin.
However, S. arundinaceum was frequently found
infested by this species in both low and mid altitude
localities. On the other hand, the C. orichalcociliellus
group was found restricted to low altitude zone
where it was recovered from seven diff erent plants: S.
arundinaceum, P. purpureum, P. maximum, Digitaria
milanjiana (Rendle) Stapf, Euclaena mexicana Schrader,
P. deustum  unberg and Hyperthelia dissoluta
(Steudel) W.D. Clayton. P
. maximum was frequently
found infested by this species in fi ve localities. In
some localities (Mombasa 3, Mombasa 6, Mombasa
7, Shimba 2 and Garissa 2), C. orichalcociliellus group
immatures were more frequent on wild hosts compared
to maize. E. saccharina was recovered from two localities
on two Cyperaceae species namely Cyperus dives Delile
and Cyperus alopecuroides Rottboll.
Non-pest stem borers among wild host plants
Stem borers varied in their distribution in wild host
plants among diff erent zones without any consistent
pattern (tabs. 2 & 3). Some localities, particularly in
the high altitude zone (Kakamega, Gatamaiyu, Kisii
1 and Kisii 2) had more larvae of “non-pest species”
on wild hosts compared to maize (tab. 2). Similar
results were recorded in the low altitude localities
namely Mombasa 6, Mombasa 7, Rift Valley 3 and
Garissa 2. About 22 non-pest borer species belonging
to 7 diff erent genera within the noctuid family have
been identifi ed.  ese genera varied in terms of species
richness among which Sesamia Guenée 1852 had 9
species followed by Sciomesa Tams and Bowden 1953
(6), Manga Bowden 1956 (2) and Busseola  urau
1904 (1).  ree unknown species were also recovered
Table 3. Proportions (%) of stem borer genera and families in diff erent altitudinal zones from wild host plants.
Parenthesis along the genera column indicates the number of species.
Super-family Family Genera <1000 1000–1500 > 1500
Noctuoidea Noctuidae Busseola (1) 1.5 0.1 14.7
Carelis (1) 0 0.0 4.8
Busseola sensu lato (3) 0 0.0 13.3
Manga (2) 23.4 9.7 1.9
Poeonoma (1) 0 0.0 15.8
Sciomesa (6) 4.6 0.8 38.8
Sesamia (9) 15.8 28.7 5.8
Pyraloidea Crambidae Chilo (5) 43.4 56.8 0.1
Other crambid species (7) 1.8 0.5 3.1
Pyralidae Eldana (1) 0.1 0.1 0.3
Other pyralid species (8) 6.9 0.3 0.3
Tortricoidea Tortricidae 11 species 2.5 2.6 1.1
Cossoidea Cossidae 2 species 0 0.4 0
Downloaded by [IRD Documentation] at 21:58 08 September 2014

Stem borers abundance in wild and cultivated habitats
369
and grouped within the unknown genera tentatively
named Busseola sensu lato.  e other genera, Poeonoma
Tams and Bowden 1953 and Carelis Bowden 1956
respectively have one species each (tab. 3). Nonetheless,
there was variation in distribution proportion among
the genera along altitudinal gradient.  e Manga genus
dominated low altitude localities (< 1000m asl) where
it constituted about 51% of noctuid larvae collected,
followed by Sesamia (34%). Sesamia was the most
important genus in the mid altitude zone, constituting
about 72% of total noctuids collected, while Sciomesa
was the most abundant genus in high altitude zones
constituting about 40% of the total noctuids, followed
by the genus Poeonoma with 16%.
Twenty-one species belonging to Crambidae and
Pyralidae families were recovered (tab. 3).  e most
abundant among these was the Crambidae family
where 2780 larvae belonging to 12 diff erent species
were identifi ed. Important in this family was the
Chilo genus, which had 5 species. Nine species were
identifi ed within the Pyralidae family of which E.
saccharina constituted about 5% of the total collection.
Tortricidae was second to Pyralidae in terms of species
richness, and third in terms of the number of larvae
collected. About 11 species were tentatively identifi ed
within Tortricidae from 180 specimens collected.  e
least number of larvae (10) as well as species (2) were
collected from the Cossidae family.
Discussion
 is fi ndings support earlier reports on variations
in the distribution of Busseola fusca and Chilo partellus
according to altitude (Seshu Reddy 1983; Songa
et al. 1998; Guofa et al. 2002).  e diff erence Nye
(1960) ascribed to climatic variations especially the
temperature. However, pest populations were higher
in maize fi elds compared to wild habitats. High pest
occurrence in maize fi elds indicates better suitability of
cultivated crops to support borer populations compared
to wild grasses. Shanower et al. (1993) showed that
survival of Sesamia calamistis and Eldana saccharina
larvae was less than 10% in Panicum maximum, Sorghum
arundinaceum, Pennisetum purpureum and Pennisetum
polystachion (L.) Schultes, while larval survival in maize
was between 19 and 30%. Low borer survival was thus
ascribed to poor host quality.
Busseola fusca was found in maize in all localities in the
mid and high altitude zones, but it was recovered from
four wild host species in fi ve localities only. Contrary to
earlier reports (Polaszek & Khan 1998; Overholt et al.
2001), only two larvae of B. fusca were recovered from P.
purpureum, which was found growing within a maize fi eld.
Laboratory studies demonstrated that B. fusca larvae were
unwilling to bore in P. purpureum stems and that adult
moths would not oviposit on that host plant (Wilkinson
1936, Calatayud et al. in lit.). Very likely reports of B.
fusca on P. purpureum in Kenya may have been a result
of the larvae moving from maize or sorghum onto P.
purpureum, or misidentifi cation. However, B. fusca was
reported to be common on P. purpureum in Central Africa
(Cameroon) (Ndemah et al. 2001a) and there may be
agreement that host range of most insects is dynamic and
often location and time-specifi c (Polaszek & Khan 1998).
Unlike B. fusca, S. calamistis was recovered from many
plant species confi rming its polyphagy corroborating
reports from West and Central Africa (Ndemah et al.
2001b).  ough wild plants are attractive to ovipositing
moths, larval survival and adult fecundity are generally
low (Shanower et al. 1993), which may explain the low
populations observed in maize fi elds surrounded by wild
hosts in Benin and Cameroon (Schulthess et al. 1997;
Schulthess et al. 2001; Ndemah et al. 2002).
Chilo partellus was found restricted to low and mid-
altitude zones with high populations in maize and low
population in the wild habitats. C. partellus populations
were higher than that of other borers supporting earlier
studies which suggested that this zone is ecologically
suitable for its establishment. Suitable climatic conditions
coupled with available alternative hosts are thought to
have favoured C. partellus (Guofa et al. 2002).  is can
explain its rapid population build up that resulted in
the displacement of indigenous Chilo orichalcociliellus
(Seshu Reddy 1983). However, there was evidence of
variation in niche occupation among these two species
in the wild as most of the C. partellus larvae were found
on S. arundinaceum while the C. orichalcociliellus group
larvae were found mainly on P. maximum.
Recorded diversity is higher than previously reported.
However, the distribution of some wild stem borers
was found restricted to either a certain plant species
or altitudinal zones.  e Manga genus was commonly
found on P. maximum in low altitude zones, while
Busseola spp were found mainly in the high altitudes.
Even with the observed variation in distribution with
altitude, importance of wild stem borers as alternative
hosts of natural enemies during the crop period cannot
be ignored. Bonhof (2000) reported high diversity and
abundance of natural enemies in maize fi elds at the
Kenyan coast during the beginning of long rainy season.
She ascribed this diversity to possible movement of
natural enemies from wild habitats where they attack
alternative host insects. Schulthess et al. (2001) reported
relatively high parasitism of S. calamistis eggs by
Telenomous spp (Hymenoptera: Scelionidae) during the
dry season in the Inland valley in Benin and Cameroon.
Wild habitats rich in alternative stem borers may attract
Downloaded by [IRD Documentation] at 21:58 08 September 2014

370
G. O. O’, B. P. L R, S. D, P. M, E. M, P.-A. C & J.-F. S
and sustain populations of natural enemies that would
eventually move to cultivated fi elds and suppress pest
populations.
 e presence and abundance of the “wild” stem
borer species in diff erent regions appear to be aff ected
by the availability of suitable host plants. Borer species
belonging to Sesamia, Sciomesa, Busseola genera as well
as Crambids, Pyralids and Tortricids constituted an
important proportion of the total collection made. Most
of the wild stem borer species were recovered from limited
number of hosts. According to Hermsmeier et al. (2001),
such specialist species are more likely to adapt to the toxic
compounds they encounter. Distribution and abundance
of some wild stem borer species may thus be attributed to
their adaptations to overcome plant defences. However,
some of the wild borer species (Busseola phaia Bowden,
1956 and Sciomesa piscator) develop easily on maize
stems exhibiting a potential to shift and become pests of
cultivated cereals.  e recent host switch of E. saccharina
from sedges to sugar cane in South Africa where it became
the key pest (Atkinson 1980) confi rms this assumption.
E. saccharina was only found on wild plants during this
study though it is an important pest of maize in West
Africa (Bosque-Perez & Mareck 1990). Nonetheless,
it could be a major threat to maize crops in Kenya if it
eventually shifts to cultivated fi elds.
Acknowledgements.  is research was supported by Institut
de Recherche pour le Développement through insect-plant
interaction unit (R072) in collaboration with International
Centre of Insect Physiology and Ecology (ICIPE).  e authors
are pleased to acknowledge the technical support off ered L.
Ngala, B. Musyoka and A. Kibe of the Noctuid Stem borer
Biodiversity (NSBB) Project.
Reference
Atkinson P.R. 1980. On the biology, distribution and natural host-plants
of Eldana saccharina Walker (Lepidoptera: Pyralidae). Journal of the
Entomological Society of Southern Africa 43: 171-194.
Blezynski S. 1970. A revison of the world species of Chilo Zincken
(Lepidoptera: Pyralidae). Bulletin of the British Museum (Natural
History) Entomology 25: 101-195.
Bonhof M.J. 2000.  e impact of predators on maize stem borers in Coastal
Kenya. PhD thesis, Wageningen University,  e Netherlands.
Bosque-Perez N.A., Mareck J.H. 1990. Distribution and species
composition of lepidopterous maize borers in southern Nigeria.
Bulletin of Entomological Research 80: 363-368
Bowden J. 1976. Stem borer ecology and strategy for control. Annals of
Applied Biology 84: 107-111.
De Groote H. 2002. Maize yield losses from stemborers in Kenya. Insect
Science and its Application 22: 89-96.
Guofa Z., Overholt W.A., Mochiah M.B. 2002. Changes in the
distribution of lepidopteran maize stem borers in Kenya from 1950’s
to 1990’s. Insect Science and its Application 21: 395-402.
Haile A., Hofsvang T. 2001. Survey of lepidopterous stem borer pests of
sorghum, maize and pearl millet in Eritrea. Crop protection 20: 151-157.
Haile A., Hofsvang T. 2002. Host plant preference of the stem borer Busseola
fusca (Fuller) (Lepidoptera: Noctuidae). Crop protection 21: 227-233.
Hermsmeier D., Schittko U., Baldwin I.T. 2001. Molecular Interactions
between the Specialist Herbivore Manduca sexta (Lepidoptera,
Sphingidae) and Its Natural Host Nicotiana attenuata. I. Large-Scale
Changes in the Accumulation of Growth- and Defense-Related Plant
mRNAs. Plant Physiology 125: 683-700.
Ingram W.R. 1958.  e lepidopterous stalk borers associated with graminae
in Uganda. Bulletin of Entomological Research 49: 367-383.
Kfi r R. 1997. Competitive displacement of Busseola fusca (Lepidoptera:
Noctuidae) by Chilo partellus (Lepidoptera: Pyralidae). Annals of the
Entomological Society of America 90: 619-624.
Ndemah R., Schulthess F., Poehling H.-M., Borgemeister C. 2001a. Natural
enemies of lepidopterous borers on maize and elephant grass in the
forest zone of Cameroon with special reference to Busseola fusca (Fuller)
(Lepidoptera: Noctuidae). Bulletin of Entomological Research. 91: 205-212.
Ndemah R., Schulthess F., Korie S., Borgemeister C., Cardwell K.F.
2001b. Distribution, relative importance and eff ect of lepidopterous
borers on maize yields in the Forest zone and Mid-Altitudes of
Cameroon. Journal of Economic Entomology 94: 1434-1444.
Ndemah R., Gounou S., Schulthess F. 2002.  e role of wild grasses
in the management of lepidopterous cereal stemborers on maize in
western Africa. Bulletin of Entomological Research 92: 507-519.
Nye I.W.B. 1960.  e Insect Pests of Graminaceous Crops in East Africa. Colonial
Research Study No. 31, Her Majesty’s Stationery Offi ce, London, 48 p.
Ong’amo G.O. 2005. An assessment of lepidopteran stem borer species distribution
in relation to diversity of wild host grasses in maize and sorghum growing
zones in Kenya. MSc thesis, Kenyatta University, Nairobi, Kenya.
Ong’amo G.O., Le Ru B.P., Dupas S., Moyal P., Calatayud P.-A., Silvain
J.-F. 2006. Distribution, pest status and agro-climatic preferences
of lepidopteran stem borers of maize in Kenya. Annales de la Société
Entomologique de France 42(2): 171-177.
Onyango F.O., Ochieng’ Odero J.P.R. 1994. Continuous rearing of
the maize stem borer Busseola fusca on an artifi cial diet. Entomologia
experimentalis et Applicata 73: 139-144.
Overholt W.A., Maes K.V.N., Goebel F.R. 2001. Field guide to stem borer
larvae of maize, sorghum and sugarcane in Eastern and Southern Africa.
ICIPE Science Press, Nairobi, 31 p.
Polaszek A., Khan Z.R. 1998. Host Plants, p. 3-10 in: Polaszek A. (ed.),
African Cereal Stem Borers: Economic importance, Taxonomy, Natural
enemies and Control. CAB International, University Press, Cambridge.
Schulthess F., Bosque-Perez N.A., Chabi-Olaye A., Gounou S., Ndemah
R., Goergen G. 1997. Exchange of Natural enemies of lepidopteran
cereal stem borers between African regions. Insect Science and its
Application 17: 97-108.
Schulthess F., Chabi-Olaye A., Georgen, G. 2001. Seasonal fl uctuations
of noctuid stem borer egg parasitism in Southern Benin with special
reference to Sesamia calamistis Hampson (Lepidoptera: Noctuidae)
and Telenomus spp. (Hymenoptera: Scelionidae) on maize. Biocontrol
Science and Technology 11: 754-757.
Seshu Reddy K.V. 1983. Study of the stem borer complex of sorghum in
Kenya. Insect Science and its Application 4: 3-10.
Seshu Reddy K.V. 1998. Maize and sorghum: East Africa, p. 25-27 in: A.
Polaszek (Ed), Africa cereal stemborers: Economic importance, Taxonomy,
Natural Enemies and Control. CAB International. University Press,
Cambridge.
Shanower T.G., Schulthess F., Bosque-Perez N.A. 1993.  e eff ects of larval
diet on the growth and development on Sesamia calamistis Hampson
(Lepidoptera: Noctuidae) and Eldana Saccharina Walker (Lepidoptera:
Pyralidae). Insect Science and its Application 14: 681-685.
Songa J.M., Overholt W.A., Mueke J.M., Okello R.O. 1998. Distribution of
stem borer species in Semi-Arid Eastern Kenya, Sixth Eastern and Southern
Africa Regional maize conference, 21st - 25th September 1998, p. 117-120.
Wilkinson H. 1936. Report of the Entomological section. Representative, 2,
Department of Agriculture, Kenya 1935, p. 60-70.
Downloaded by [IRD Documentation] at 21:58 08 September 2014