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Spatio-temporal dynamics of multi-species pest communities and the interactions between them influence the structure of pest complex that attack crops. In East and Southern Africa, cereal crops, especially maize, is attacked by a complex of lepidopteran stemborer species made up of Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae), and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). There is inadequate information on the extent of single- and multi-species infestations by this pest complex, their current spatio-temporal variations, and the primary abiotic factors that influence these. Furthermore, the recent invasion of the fall armyworm, Spodoptera frugiperda J.E. Smith, in sub-Saharan Africa will likely influence this stemborer community structure. Sampling was conducted in maize fields to record stemborer species and larval numbers from infested plants, in 28 localities found in six agro-ecological zones (AEZs) of Kenya and parts of Tanzania, as well as in one locality in the mid-altitudes where the three stemborer species occurred together. Both single- and multi-species stemborer communities characterized infestation of maize at field and plant levels, but varied in proportions between the AEZs. Infestation patterns and larval densities varied between seasons at mid-locality stemborer communities followed a clustered distribution pattern. Temperature was the most significant abiotic factor influencing the composition of stemborer communities at all spatial scales. Rainfall was significant only at the local scale. Results are discussed in relation to current stemborer community structures in maize fields and what the likely potential implications are, in the light of climate change and the recent establishment of the fall armyworm in Africa

Spatio-temporal dynamics of multi-species pest communities and the interactions between them influence the structure of pest complex that attack crops. In East and Southern Africa, cereal crops, especially maize, is attacked by a complex of lepidopteran stemborer species made up of Busseola fusca (Fuller) and Sesamia calamistis Hampson (Lepidoptera: Noctuidae), and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). There is inadequate information on the extent of single- and multi-species infestations by this pest complex, their current spatio-temporal variations, and the primary abiotic factors that influence these. Furthermore, the recent invasion of the fall armyworm, Spodoptera frugiperda J.E. Smith, in sub-Saharan Africa will likely influence this stemborer community structure. Sampling was conducted in maize fields to record stemborer species and larval numbers from infested plants, in 28 localities found in six agro-ecological zones (AEZs) of Kenya and parts of Tanzania, as well as in one locality in the mid-altitudes where the three stemborer species occurred together. Both single- and multi-species stemborer communities characterized infestation of maize at field and plant levels, but varied in proportions between the AEZs. Infestation patterns and larval densities varied between seasons at mid-locality stemborer communities followed a clustered distribution pattern. Temperature was the most significant abiotic factor influencing the composition of stemborer communities at all spatial scales. Rainfall was significant only at the local scale. Results are discussed in relation to current stemborer community structures in maize fields and what the likely potential implications are, in the light of climate change and the recent establishment of the fall armyworm in Africa

Lepidopteran stemborers are a serious pest of maize in Africa. While farmers have adopted cultural control practices at the field scale, it is not clear how these practices affect stemborer infestation levels and how their efficacy is influenced by landscape context. The aim of this 3-year study was to assess the effect of field and landscape factors on maize stemborer infestation levels and maize productivity. Maize infestation levels, yield and biomass production were assessed in 33 farmer fields managed according to local practices. When considering field level factors only, plant density was positively related to stemborer infestation level. During high infestation events, length of tunnelling was positively associated with planting date and negatively with the botanical diversity of hedges. However, the proportion of maize crop in the surrounding landscape was strongly and positively associated with length of tunnelling at 100, 500, 1000 and 1500 m radius, and overrode field level management factors when considered together. Maize grain yield was positively associated with plant density and soil phosphorus content, and not negatively associated with the length of tunnelling. Our findings highlight the need to consider a landscape approach for stemborer pest management, but also indicate that maize is tolerant to low and medium infestation levels of stemborers.

The host plant range of pests can have important consequences for its evolution, and plays a critical role in the emergence and spread of a new pest outbreak. This study addresses the ecological genetics of the indigenous African maize stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae), in an attempt to investigate the evolutionary forces that may be involved in the recent host range expansion and establishment of this species in Ethiopian and southern African sugarcane. We used populations from Ethiopia, Zimbabwe, and South Africa to examine whether the host range expansion patterns shared by the Ethiopian and the southern African populations of B. fusca have evolved independently. Base-pair differences in the cytochrome oxidase I (COI) gene were used to characterize haplotype diversity and phylogenetic relationships. There were seven haplotypes among the 30 sequenced individuals collected on four host plant species from 17 localities in the four countries. Of the seven COI haplotypes identified, the two major ones occurred in both sugarcane and maize. Genetic analyses revealed no detectable genetic differentiation between southern African B. fusca populations from maize and sugarcane (FST = 0.019; P = 0.24). However, there was strong evidence of variation in genetic composition between populations of the pest from different geographic regions (FST = 0.948; P < 0.001). The main implication of these findings is that the B. fusca populations in maize in southern Africa are more likely to shift to sugarcane, suggesting that ecological opportunity is an important factor in host plant range expansion by a pest

The host plant range of pests can have important consequences for its evolution, and plays a critical role in the emergence and spread of a new pest outbreak. This study addresses the ecological genetics of the indigenous African maize stem borer, Busseola fusca (Fuller) (Lepidoptera: Noctuidae), in an attempt to investigate the evolutionary forces that may be involved in the recent host range expansion and establishment of this species in Ethiopian and southern African sugarcane. We used populations from Ethiopia, Zimbabwe, and South Africa to examine whether the host range expansion patterns shared by the Ethiopian and the southern African populations of B. fusca have evolved independently. Base-pair differences in the cytochrome oxidase I (COI) gene were used to characterize haplotype diversity and phylogenetic relationships. There were seven haplotypes among the 30 sequenced individuals collected on four host plant species from 17 localities in the four countries. Of the seven COI haplotypes identified, the two major ones occurred in both sugarcane and maize. Genetic analyses revealed no detectable genetic differentiation between southern African B. fusca populations from maize and sugarcane (FST = 0.019; P = 0.24). However, there was strong evidence of variation in genetic composition between populations of the pest from different geographic regions (FST = 0.948; P < 0.001). The main implication of these findings is that the B. fusca populations in maize in southern Africa are more likely to shift to sugarcane, suggesting that ecological opportunity is an important factor in host plant range expansion by a pest

Napier grass, Pennisetum purpureum (Schumach), in combination with intercrops has been used successfully in habitat management for maize stem borers in Africa. The use of Napier grass only as a trap or barrier plant for Chilo partellus (Lepidoptera: Crambidae) and Busseola fusca (Fuller) (Lepidoptera: Noctuidae) was evaluated in this study. Napier grass borders were planted only on two sides of small-scale farmers’ maize fields, since planting of perennial trap crops on all sides of fields hampered mechanical cultivation. C. partellus was the dominant borer species, followed by B. fusca and Sesamia calamistis (Hampson) (Lepidoptera: Noctuidae). Reductions between 0% and 27.4% in the incidence of borerinfested plants were observed on the 16 farms evaluated in this study. The results show that Napier grass as trap/barrier crop suppresses stem borer numbers in maize fields

Napier grass, Pennisetum purpureum (Schumach), in combination with intercrops has been used successfully in habitat management for maize stem borers in Africa. The use of Napier grass only as a trap or barrier plant for Chilo partellus (Lepidoptera: Crambidae) and Busseola fusca (Fuller) (Lepidoptera: Noctuidae) was evaluated in this study. Napier grass borders were planted only on two sides of small-scale farmers’ maize fields, since planting of perennial trap crops on all sides of fields hampered mechanical cultivation. C. partellus was the dominant borer species, followed by B. fusca and Sesamia calamistis (Hampson) (Lepidoptera: Noctuidae). Reductions between 0% and 27.4% in the incidence of borerinfested plants were observed on the 16 farms evaluated in this study. The results show that Napier grass as trap/barrier crop suppresses stem borer numbers in maize fields

Based on surface area, South Africa is currently ranked the eighth in planting genetically modified (GM) crops in the world. Bt maize (MON810) has been grown to control lepidopterous stem borers in South Africa since its first release during 1998. The first report of resistance of the African maize stem borer, Busseola fusca (Lepidoptera: Noctuidae) and poor compliance to refuge requirements that could have contributed to resistance development prompted this study which was done in the main maize production area of South Africa. Objectives were to evaluate farmer’s perceptions of the regulatory aspects guiding the planting of Bt maize and refugia and how it was applied between 1998 and 2010. This study involved 105 commercial farmers covering 87 778 ha of maize throughout the main maize production region on the Highveld of South Africa. A questionnaire survey was conducted and addressed signing of technical agreements upon purchasing GM seed, refuge compliance, pest management practices, perceived benefits and risks relating to Bt maize. Compliance with refugia requirements was low especially during the initial 5–7 years after release. An alarmingly high number of farmers applied insecticides as preventative sprays on Bt maize and refugia irrespective of stem borer infestation levels. A large proportion of farmers reported significant borer infestation levels on Bt maize and between 5% and 93% farmers in all districts applied insecticides to Bt maize to limit borer damage, indicating that the occurrence of resistance is more wide-spread in the country than previously thought. This study shows irresponsible management of GM crop technology by farmers, chemical and seed companies. Concerns and perceptions of farmers in South Africa seem to differ from those in Europe. South African farmers perceived little, if any, negative impact on non-target organisms and remain positive about the technology in spite of resistance development. Other studies indicated that European

Based on surface area, South Africa is currently ranked the eighth in planting genetically modified (GM) crops in the world. Bt maize (MON810) has been grown to control lepidopterous stem borers in South Africa since its first release during 1998. The first report of resistance of the African maize stem borer, Busseola fusca (Lepidoptera: Noctuidae) and poor compliance to refuge requirements that could have contributed to resistance development prompted this study which was done in the main maize production area of South Africa. Objectives were to evaluate farmer’s perceptions of the regulatory aspects guiding the planting of Bt maize and refugia and how it was applied between 1998 and 2010. This study involved 105 commercial farmers covering 87 778 ha of maize throughout the main maize production region on the Highveld of South Africa. A questionnaire survey was conducted and addressed signing of technical agreements upon purchasing GM seed, refuge compliance, pest management practices, perceived benefits and risks relating to Bt maize. Compliance with refugia requirements was low especially during the initial 5–7 years after release. An alarmingly high number of farmers applied insecticides as preventative sprays on Bt maize and refugia irrespective of stem borer infestation levels. A large proportion of farmers reported significant borer infestation levels on Bt maize and between 5% and 93% farmers in all districts applied insecticides to Bt maize to limit borer damage, indicating that the occurrence of resistance is more wide-spread in the country than previously thought. This study shows irresponsible management of GM crop technology by farmers, chemical and seed companies. Concerns and perceptions of farmers in South Africa seem to differ from those in Europe. South African farmers perceived little, if any, negative impact on non-target organisms and remain positive about the technology in spite of resistance development. Other studies indicated that European

English: Since conventional sources of resistance to stem borers are not adapted to South African conditions, resistance has to be introgressed into locally adapted breeding material. Combining ability for resistance possibly differs between heterotic groups, and susceptible elite material do not necessarily respond similarly in crosses with sources of resistance from different genetic backgrounds. From earlier work conducted under greenhouse conditions it was observed that larval development rate possibly differs with difference in time of the year. The objective of this study was to determine which combinations of resistant sources with local elite susceptible material could provide the best expression of resistance. Susceptible and resistant lines were crossed in various combinations to obtain semi-resistant single and double crosses with various resistance levels. These were compared to susceptible and resistant standards in field trials. Plants were artificially infested with neonate larvae. Evaluations of leaf feeding damage, stem damage, ear damage, plant height reduction and grain yield were subjected to factorial analysis, using planting date and infestation as factors. Two resistant lines and one semi-resistant single cross were identified that seemed to provide particularly high levels of resistance. However, the study did not successfully identify which resistance source should be used in combination with which heterotic group, neither did resistance derived from different sources seem to compliment each other. Using principal component analysis of data on double crosses, no pattern could be observed that indicated crosses comprising more than one resistant parent to be more resistant than those in which only one resistant parent featured, whereas variance in resistance did not seem to relate to heterotic patterns. A further aspect of the study involved investigation into the effect of variance in planting date on the expression of resistance. Various li, Afrikaans: Konvensionele bronne van weerstand teen mieliestamruspers is nie aangepas vir SuidAfrikaanse toestande nie en moet dus geintegreer word in plaaslik aangepaste teelmateriaal. Kombineervermoë vir weerstand verskil moontlik tussen heterotiese groepe, en vatbare elite materiaal reageer nie noodwendig eenders in kruisings met bronne van weerstand van verskillende genetiese agtergronde nie. Uit vroeëre werk wat onder glashuistoestande gedoen is, is bevind dat die larwale ontwikkelingstempo moontlik verskil met verskille in die tyd van die jaar. Die doel van die studie was om te bepaal watter kombinasies van weerstandsbronne met plaaslike elite vatbare materiaal die beste moontlike bestandheid kan lewer. Vatbare en bestande lyne is gekruis in verskillende kombinasies om semiweerstandbiedende enkel- en dubbelkruisings met verskillende weerstandsvlakke te verkry. Die kruisings is in veldproewe vergelyk met vatbare en bestande standaarde. Plante is kunsmatig besmet met pasuitgebroeide larwes. Evaluasies van blaarbeskadiging, stamskade, kopskade, planthoogteverskille en graanopbrengs is aan faktoriaalontledings onderwerp waar plantdatum en infestasie as faktore gebruik is. Twee bestande lyne en een semibestande enkelkruis is geiidentifiseer wat hoë vlakke van weerstand gelewer het. Die studie het egter nie suksesvol geiidentifiseer watter weerstandsbronne in watter kombinasies met verskillende heterotiese groepe gebruik moet word nie. Dit het ook nie kon bevestig dat weerstandsbronne uit veskillende agtergronde mekaar komplimenteer nie. Hoofkomponent analise van die data uit dubbelkruisings het geen weerstandspatrone kon aantoon nie en kruisings waarin meer as een bestande ouer gebruik is, het nie hoër weerstand gehad as kruisings waarin slegs een ouer gebruik is nie. Variasie in weerstand het ook nie met heterotiese patrone verband gehou nie. ‘n Verdere aspek van die studie het gehandel oor die effek van variasie in plantdatum op die uitdrukking van weerstand. Vers

Les insectes foreurs de tige et d'épi sont des ravageurs majeurs du mais en Côte d'Ivoire. Trois espèces, appartenant à l'ordre des Lépidoptères, représentent un réel danger pour les maïsiculteurs : deux foreurs de tige, Eldana saccharinu Walker (Pyralidae) et Busseola fusca (Fuller) (Noctuidae), et un foreur d'épi, Mussidia nigrivenella Ragonot (Pyralidae). L'étude de l'abondance de ces espèces dans les diverses régions du puys et nu cours des cycles de culture successifs a montré que la densité de foreurs était minimale sur les cycles mis en place peu après la fin de la saison sèche, en moi-juin dans le Nord et en mars-avril dans les autres régions. Les dégâts les plus importants sont observés dans la région du centre sur le cycle semé en juin-juillet. L'infestation est ensuite réduite principalement par le parasitisme des oeufs. Des modèles statistiques permettant d'estimer les pertes de récolte dues à ces foreurs sont établis. Ces modèles sont fondés soit sur les nombres d'insectes par plante à 40 et 80 jours après la levée (pour les foreurs de tige), soit sur les dégâts observés 80 jours après la levée. Ils montrent en particulier que les attaques de début de cycle par Busseola fusca sont les plus dangereuses. Des méthodes de lutte agronomique et chimique sont proposées.

English: Investigations on various aspects of stalk borers of maize and sorghum were conducted in Lesotho during the 1995/96, 1996/97 and 1997/98 growing seasons. Aspects investigated were their distribution and relative abundance on these two crops; seasonal moth flight pattern of Busseola fusca; impact of natural stalk borer populations on maize and sorghum; response of some maize and sorghum varieties/hybrids to artificial infestations with B.fusca and Chilo partellus respectively; farmers' perceptions and farm management practices with regard to the management of stalk borers; relative efficacy of insecticides used for C. partellus control in Lesotho; effect of planting date of maize on B.fusca infestations; effect of intereropping with beans on B. fusca infestations in maize, and relative abundance of natural enemies of B. fusca and C. partellus. These investigations provided the following results: B. fusca was distributed throughout Lesotho and was important on both maize and sorghum. C. partellus occurred only in the central lowlands where it attacked only sorghum. Seasonal B. fusca moth flight activity was characterised by distinct periods of high and low activity, with three and two to three generations of moths per season in the lowlands and mountains respectively. Infestations of B. fusca in Lesotho caused substantial yield losses in susceptible maize varieties and hybrids. Lesotho's maize varieties and hybrids were observed to be susceptible, with yield losses of up to 39.4% observed under field conditions. Their susceptibility was further demonstrated through artificial infestations in glasshouse and field studies. The glasshouse study showed that the levels of antibiosis and antixenosis resistance to B. fusca in these varieties and hybrids were low, while the field studies showed only moderate resistance to foliar damage. Lesotho's sorghum varieties exhibited susceptibility to stalk borer damage, both under field conditions and artificial infestations, Afrikaans: Ondersoeke na verskeie aspekte van sorghum en mieliestamboorders in Lesotho is gedurende die 1995/96, 1996/97 en 1997/98 seisoene gedoen. Ondersoek is gedoen na die verspreiding en talrykheid van stamboorders op hierdie gewasse; seisoenale motvlugpatroon van Busseola fusca; die impak van natuurlike stamboorderpopulasies op mielies en sorghum; die reaksie van mielie en sorghum varieteite en basters op kunsmatige besmetting van B. fusca en Chilo partellus respektiewelik; boere se persepsie van stamboorders asook boerderypraktyke wat verband kan hou met bestuur van stamboorders; die relatiewe effektiwiteit van insekdoders wat gebruik word vir stamboorderbeheer in Lesotho; die effek van plantdatum van mielies op B. fusca skade; die effek vaninter-verbouing met boontjies op B. fusca voorkoms en skade in mielies asook die voorkoms en talrykheid van natuurlike vyande van B. fusca en C. partellus. Hierdie ondersoeke het die volgende bevindinge opgelewer: B. fusca kom voor in alle produksiegebiede in Lesotho en is belangrik op mielies en sorghum. C. partellus kom slegs in die sentrale laaglande voor waar dit net sorghum beskadig. Die seisoenale aktiwiteit van B. fusca word gekenmerk deur afgebakende periodes van hoë en lae motvlugaktiwiteit. Drie motgenerasies per seisoen kom in die laaglande voor en twee tot drie generasies in die hoogliggende bergagtige gebiede. B. fusca besmetting veroorsaak aansienlike oesverliese in mielievarieteite en basters. Plaaslike Lesotho mielievarieteite en basters is vatbaar vir stamboorderskade en oesverlies van tot 39.4 % is onder veldtoestande waargeneem. Vatbaarheid van hierdie varieteite en basters is bevestig deur evaluasies onder kunsmatige besmettings onder glashuistoestande. Glashuis-studies het aangetoon dat die vlakke van antibiose en antixenose weerstand in hierdie varieteite en basters laag is, terwyl veldstudies slegs geringe blaarvoedingsweerstand getoon het. Plaaslike Lesotho sorghum varieteite was vatbaar vir stamboo

Les insectes foreurs de tige et d'épi sont des ravageurs majeurs du mais en Côte d'Ivoire. Trois espèces, appartenant à l'ordre des Lépidoptères, représentent un réel danger pour les maïsiculteurs : deux foreurs de tige, Eldana saccharinu Walker (Pyralidae) et Busseola fusca (Fuller) (Noctuidae), et un foreur d'épi, Mussidia nigrivenella Ragonot (Pyralidae). L'étude de l'abondance de ces espèces dans les diverses régions du puys et nu cours des cycles de culture successifs a montré que la densité de foreurs était minimale sur les cycles mis en place peu après la fin de la saison sèche, en moi-juin dans le Nord et en mars-avril dans les autres régions. Les dégâts les plus importants sont observés dans la région du centre sur le cycle semé en juin-juillet. L'infestation est ensuite réduite principalement par le parasitisme des oeufs. Des modèles statistiques permettant d'estimer les pertes de récolte dues à ces foreurs sont établis. Ces modèles sont fondés soit sur les nombres d'insectes par plante à 40 et 80 jours après la levée (pour les foreurs de tige), soit sur les dégâts observés 80 jours après la levée. Ils montrent en particulier que les attaques de début de cycle par Busseola fusca sont les plus dangereuses. Des méthodes de lutte agronomique et chimique sont proposées.

A l'Icrisat-Cirad (Mali), des études menées sur milieu nutritif artificiel au laboratoire, ont montré un effet létal de l'huile brute de Pourghère (#Jatropha curcas#), à la concentration de 1%, et des esters de phorbol à partir de la concentration de 0,025%, sur #Sesamia calamistis#, et de l'huile brute dès la concentration de 0,1% sur #Busseola fusca#. En revanche, l'application de broyats de graines de pourghère, Neem ou Ricin dans le cornet foliaire de plants d'une variété locale de sorgho, infestés artificiellement avec des insectes d'élevage (dans le cadre d'essais en parcelles expérimentales), n'a pas entraîné de réduction significative des dégâts de #B. fusca#. Un effet bénéfique d'extraits de graines de pourghère formulés en ULV ou CE sur les dégâts de punaises des panicules (bien que modeste par rapport à la protection chimique offerte par la deltaméthrine) a été mis en évidence dans le cadre d'essais impliquant quatre variétés soumises à l'infestation naturelle, et ce à des doses très faibles pour des produits d'origine naturelle.

A l'Icrisat-Cirad (Mali), des études menées sur milieu nutritif artificiel au laboratoire, ont montré un effet létal de l'huile brute de Pourghère (#Jatropha curcas#), à la concentration de 1%, et des esters de phorbol à partir de la concentration de 0,025%, sur #Sesamia calamistis#, et de l'huile brute dès la concentration de 0,1% sur #Busseola fusca#. En revanche, l'application de broyats de graines de pourghère, Neem ou Ricin dans le cornet foliaire de plants d'une variété locale de sorgho, infestés artificiellement avec des insectes d'élevage (dans le cadre d'essais en parcelles expérimentales), n'a pas entraîné de réduction significative des dégâts de #B. fusca#. Un effet bénéfique d'extraits de graines de pourghère formulés en ULV ou CE sur les dégâts de punaises des panicules (bien que modeste par rapport à la protection chimique offerte par la deltaméthrine) a été mis en évidence dans le cadre d'essais impliquant quatre variétés soumises à l'infestation naturelle, et ce à des doses très faibles pour des produits d'origine naturelle.

Les conditions agronomiques et économiques de production des céréales en Afrique (riz, maïs, sorgho) conduisent à privilégier, dans le cadre de la lutte intégrée contre les foreurs des tiges, la voie de la résistance ou de la tolérance variétale à ces ravageurs. Cette option suppose une bonne connaissance des mécanismes d'infestation des cultures et la maîtrise des moyens d'évaluation de la résistance de la plante hôte aux insectes. L'article présente quelques cas d'études concernant trois foreurs africains : #Busseola fusca#, #Sesamia calamistis# et #Eldana saccharina# et un foreur asiatique et européen : #Chilo suppressalis#.

Les conditions agronomiques et économiques de production des céréales en Afrique (riz, maïs, sorgho) conduisent à privilégier, dans le cadre de la lutte intégrée contre les foreurs des tiges, la voie de la résistance ou de la tolérance variétale à ces ravageurs. Cette option suppose une bonne connaissance des mécanismes d'infestation des cultures et la maîtrise des moyens d'évaluation de la résistance de la plante hôte aux insectes. L'article présente quelques cas d'études concernant trois foreurs africains : #Busseola fusca#, #Sesamia calamistis# et #Eldana saccharina# et un foreur asiatique et européen : #Chilo suppressalis#.