Studies on stalk borers of maize and sorghum in Lesotho
| dc.contributor.advisor | Van den Berg, Johnnie | |
| dc.contributor.advisor | Van der Linde, T. C de K. | |
| dc.contributor.author | Ebenebe, Adama Audu | |
| dc.date.accessioned | 2018-04-10T10:05:36Z | |
| dc.date.available | 2018-04-10T10:05:36Z | |
| dc.date.issued | 1998-11 | |
| dc.description.abstract | 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 with C. partellus. A glasshouse study also found antibiosis to be the main resistance mechanism against C. partellus larvae in whorls of resistant sorghum genotypes. The variety Tenant White, exhibited tolerance to damage, both under natural and artificial infestations.Lesotho's farmers regarded stalk borers as important pests. The commonly employed control measure was insecticide application. Although the use of routine farm management practices has potential for suppressing borer populations, they were not utilised in this regard. Comparison of the efficacy of six insecticides used for stalk borer control in Lesotho indicated granular formulations beta-cyfluthrin 0.05 % and carbaryl 2.5 % to be more effective against C. partellus larvae in sorghum whorls than spray formulations. Early planting of maize (in November) substantially reduced damage and yield loss caused by B.fusca. Intereropping maize with beans reduced damage and yield loss caused by B. fusca in maize. Furthermore, alternating rows of maize with rows of beans was more effective than alternating maize with beans within a row. The braconids Bracon sesamiae, Cotesia sesamiae, Euvipio sp. and Habrobracon brevicornis parasitized B. fusca larvae. Only B. sesamiae and C. sesamiae were recorded on C. partellus larvae. An unidentified ichneumonid was reared from C. partellus pupae, while a red ant species Dory/us sp. (Formicidae) was recorded as a predator of both B. fusca and C. partellus larvae. However, the activity of these natural enemies was generally low, increasing only towards the end of the growing season. These investigations have shown that stalk borer infestations are economically important in Lesotho. However, adopting such cultural practices as planting date adjustment, intereropping and destruction of crop residues can limit infestations. These practices, together with limited insecticide use, should form components of an integrated stalk borer management system. Future research efforts in Lesotho need to include the identification and development of maize and sorghum varieties and hybrids with high yields even under stalk borer infestations. Where such varieties are open-pollinated, they will be of particular benefit to the resource-poor farmers, who may not be able to afford hybrid seeds. | en_ZA |
| dc.description.abstract | 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 stamboorderskade, onder beide veldtoestande en kunsmatige besmetting van C. partellus. 'n Glashuis-studie het getoon dat antibiose die belangrikste weerstandsmeganisme was tydens die kelkstadium van die weerstandbiedende genotipes wat as kontroles ingeluit is. Die varieteit, Tenant White, het verdraagsaamheid vir skade getoon, beide onder natuurlike en glashuistoestande. Boere in Lesotho beskou stamboorders as belangrike plae. Die mees algemene metode van beheer is deur gebruik te maak van chemiese insekdodertoediening. Alhoewel die benutting van roetine boerderypraktyke potensiaal het om plaagpopulasies en stamboorderskade te onderdruk, word dit geensins in hierdie verband aangewend nie. Evaluasie van die effektiwiteit van ses insekdoders wat beskikbaar is vir C. partellus beheer in Lesotho het getoon dat die korrelformulasies, beta-siflutrien 0.05 % en karbaril 2.5 %, meer effektief is as spuitformulasies. Vroeë mielieaanplantings (in November) het 'n betekenisvolle afuame in B. fusca skade en oesverlies tot gevolg gehad. Interverbouing van mielies met boontjies het veminderde B. fusca skade en geassosieërde oesverlies tot gevolg gehad. Afwisselende rye van mielies en boontjies was meer effektief in die vermindering van B. fusca skade as wanneer mielie- en boontjieplante afwisselend binne die ry geplant word. Die braconids Bracon sesamiae, Cotesia sesamiae, Euvipio sp. en Habrobracon brevicornis is waargeneem as parasiete van B. fusca larwes. Slegs Bracon sesamiae en Cotesia sesamiae is waargeneem as parasiete van C. partellus larwes. 'n Ongeïdentifiseerde icneumonid is uit 'n C. partellus papie uitgeteel en 'n rooimier, Dory/us sp. (Formicidae) is as 'n predator van beide B. fusca en C. partellus aangeteken. Die aktiwiteit van natuurlike vyande was oor die algemeen laag en het slegs teen die einde van die produksieseisoen toegeneem. Tydens hierdie studie is gevind dat stamboorders ekonomies belangrik is in Lesotho. Die benutting van kulturele praktyke soos aanpassing in plant datum, interverbouing en vernietiging van plantreste kan stamboorderbesmettings onderdruk. Hierdie praktyke, tesame met die minimum gebruik van insekdoders, behoort in 'n geïntegreerde beheerstelsel ingeskakel te word. Toekomstige navorsingsaksies in Lesotho moet gemik wees op die identifisering en ontwikkeling van mielie en sorghumvarieteite en basters met hoë opbrengspotensiaal onder stamboorderbesmettings. Veraloopbestuifde varieteite sal tot die voordeel van hulpbron-arm boere wees wat nie bastersaad kan bekostig nie. | en_ZA |
| dc.identifier.uri | http://hdl.handle.net/11660/8175 | |
| dc.language.iso | en | en_ZA |
| dc.publisher | University of the Free State | en_ZA |
| dc.rights.holder | University of the Free State | en_ZA |
| dc.subject | Busseola fusca | en_ZA |
| dc.subject | Chilo partellus | en_ZA |
| dc.subject | Parasitoids | en_ZA |
| dc.subject | Predators | en_ZA |
| dc.subject | Sorghum -- Diseases and pests -- Lesotho | en_ZA |
| dc.subject | Corn -- Diseases and pests -- Lesotho | en_ZA |
| dc.subject | Stem borers -- Lesotho | en_ZA |
| dc.subject | Thesis (Ph.D. (Zoology and Entomology))--University of the Free State, 1998 | en_ZA |
| dc.title | Studies on stalk borers of maize and sorghum in Lesotho | en_ZA |
| dc.type | Thesis | en_ZA |