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The population dynamics of busseola fusca (Fuller) was studied from 1997 to 1999 at Halhale and Halhal Begos, located at altitudes of 1960 and 1850 m above sea level respectively in the highlands of Eritrea. Sowing was done in early April in Halhale and late June in Halhal Begos throughout the study period. All agronomic practices recommended for sorghum production in the two areas were followed to ensure good crop stand, except for application of pesticides. A total of 15 generations, nine in Halhale and six in Halhal Begos were observed during the study periods. Busseola fusca had three and two generations per year in Halhale and Halhal Begos, respectively. Peak egg laying at Halhale was in early May, July and early September, while at Halhal Begos it was in July and early September. The study revealed that stage-specific mortalities of B. fusca were caused by infertility, disappearance (predation by ants and earwigs, lack of suitable host, abiotic factors), residuals and parasitoids. The key mortality factor was disappearance of small larvae (35–66 % mortality). The mortality of the other stages was low but had a composite effect on the overall generation mortality. The mortality of small larvae was density-dependent and density-independent at Halhale and Halhal Begos, respectively. The changes in population between generations were due to small larval mortality of B. fusca from one generation to the next. The life table study showed that mortality due to natural factors did not reduce B. fusca population below the damage level. Integrated management strategies are discussed to reduce the damage caused by B. fusca on sorghum.

While observational studies led to the assumption that water or moisture (W/M) is a prerequisite for diapause development, the experimental research indicates rather the opposite: usually W/M is needed as late as for the post-diapause resumption of morphogenesis. Recent examples for this type of regulation of dormancy are given: Eggs of the tettigoniid Stictophaula armata, eggs of the grasshopper Oedaleus senegalensis, adults of the bruchid Bruchidius atrolineatus, adults of the endomychid Stenotarsus subtilis (= S. rotundus). In the late diapause of the noctuid Busseola fusca and in eggs of the chrysomelid Homichloda barkeri, moisture is assumed to be the diapause terminating cue. Fall in temperature is assumed decisive for termination of pupal diapause in the saturniid Schausiella santarosensis, although the effect of intense rain after a long dry period has not yet been excluded. Effects of intense changes in environmental conditions and of gradual decrease in diapause intensity with time have often been neglected.

Cotesia sesamiae (Cameron) is an indigenous larval endoparasitoid that attacks mid- to late-stage gramineous stem borer larvae in Africa. Two biotypes of C. sesamiae have been reported with differential abilities to suppress the immune system of Busseola fusca Fuller. Eggs of a C. sesamiae population from Mombasa were encapsulated, whereas eggs of a population from Kitale were not. Total and differential hemocytes were counted in larvae of B. fusca at six times (2 h, 14 h, 24 h, 72 h, 120 h, 168 h) after being exposed to parasitoids from Kitale and Mombasa. The total numbers of hemocytes in a larva parasitized by the C. sesamiae population from Mombasa were higher as compared with larvae parasitized by the C. sesamiae population from Kitale. Plasmatocytes, in particular, were reduced in larvae parasitized by C. sesamiae from western Kenya from 72 to 168 h after oviposition. Our results suggest that plasmatocytes probably play an important role in the immune response of B. fusca. Significant proportions of the host larvae were still at the larval stage for those parasitized by C. sesamiae from Mombasa and another species of Cotesia, Cotesia flavipes Cameron at day 12. A reduction of B. fusca larval weight was observed on day 12 after oviposition by C. sesamiae from Kitale.

The role of volatiles from stemborer host and non-host plants in the host-finding process of Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae) a pupal parasitoid of Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) was studied. The non-host plant, molasses grass (Melinis minutiflora Beauv. (Poaceae)), is reported to produce some volatile compounds known to be attractive to some parasitoid species. The studies were conducted to explore the possibility of intercropping stemborer host plants with molasses grass in order to enhance the foraging activity of D. busseolae in such a diversified agro-ecosystem. Olfactometric bioassays showed that volatiles from the host plants maize, Zea mays L., and sorghum, Sorghum bicolor (L.) (Poaceae), were attractive to the parasitoid. Infested host plants were the most attractive. Volatiles from molasses grass were repellent to the parasitoid. Further tests showed that volatiles from infested and uninfested host plants alone were preferred over those from infested and uninfested host plants combined with the non-host plant, molasses grass. In dual choice tests, the parasitoid did not discriminate between volatiles from maize infested by either of the two herbivore species, C. partellus or Busseola fusca Fuller (Lepidoptera: Noctuidae). Volatiles from sorghum infested by C. partellus were preferred over those from C. partellus-infested maize. The study showed that the pupal parasitoid D. busseolae uses plant volatiles during foraging, with those from the plant?herbivore complex being the most attractive. The fact that volatiles from molasses grass were deterrent to the parasitoid suggested that intercropping maize or sorghum with molasses grass was not likely to enhance the foraging behaviour of D. busseolae. Volatiles from the molasses grass may hinder D. busseolae's host location efficiency

1. Parasitoids were reared from four species of lepidopteran stem borer collected in maize in southern coastal Kenya from 1992 to 1999. The stem borers included three native species, Sesamia calamistis Hampson, Busseola fusca Fuller, and Chilo orichalcociliellus (Strand), and one exotic borer, Chilo partellus (Swinhoe). A total of 174 663 caterpillars was collected, of which 12 645 were parasitised. 2. Twenty-six primary parasitoid species were reared from the exotic borer, C. partellus, indicating a rapid accumulation of native parasitoids on the alien borer. 3. The three most abundant parasitoids were the larval parasitoids Cotesia sesamiae Cameron, Cotesia flavipes (Cameron), and the pupal parasitoid Pediobius furvus Gahan. The pupal parasitoid Dentichasmias busseolae Heinrich and the larval parasitoid Goniozus indicus Ashmead were also common. All used an ingress-and-sting method of attack. 4. Cotesia flavipes, introduced into Kenya in 1993, was found in all seasons from 1997 onwards, and has become the most abundant stem borer larval parasitoid in the area. A native congener, Cotesia sesamiae, appeared in all seasons from 1992 to 1999. Together, these two parasitoids accounted for 83.3% of the parasitised borers. 5. Thirty parasitoid species were recovered in Kilifi district, 27 in Kwale, and 15 in Taita Taveta. Parasitism was much greater in Taita Taveta district than in Kilifi or Kwale districts.

The effect of vegetation, intercropping, and Telenomus spp. egg parasitism during the vegetative stage of maize on Busseola fusca (Fuller) (Lepitoptera: Noctuidae) infestations and maize yields at harvest were studied during two consecutive cropping seasons, in the humid forest zone of Cameroon. Six locations grouped into three blocks, representing gradients in human population densities of 15–88 inhabitants/km2 were chosen. The fields were located at 20–90 min walking distance from the next road. Differences between blocks in the measured variables were mostly not significant indicating that the population density gradient was not strong enough to affect length of fallow period and thereby vegetation, the population dynamics of pests and natural enemies, and maize yields in forest fields. Numbers of egg batches per plant but also egg parasitism by and sex ratio of Telenomus spp. were significantly higher during the second than the first season (66.9 versus 19.9% and 0.67 versus 0.21, respectively). As a result, the number of borers per plant was only 0.22 versus 0.73 during the first season. Similarly, total mortality of immature B. fusca was 60.5% during the first and 93.2% during the second season. The seasonal differences in unexplained mortality was probably because rainfall caused drowning of migrating first instars. High mean parasitoid mortality at the beginning of the first season was probably caused by high superparasitism promoted by low host density conditions. Across seasons, abundance of grasses in the surroundings of a field was negatively related to egg batch density. Likewise, numbers of B. fusca decreased with increasing density of the nonhost cassava in the field, indicating increasing mortality of migrating larvae. Egg numbers per plant was negatively and egg parasitism or parasitoid sex ratio was positively related to yield.

The inheritance of resistance to the African stem borer, Busseola fusca, in maize was investigated by means of line x tester analyses in the F1 to F4 generations of crosses between 18 susceptible inbred lines and two resistant testers of common genetic background. Based on artificial infestation of plants followed by evaluation of leaf feeding damage, additive gene action was found to be significant for resistance, whereas dominance was nonsignificant in all cross combinations, using phenotypic assessment of gene expression in various generations. However, estimates of genetic components showed both additive and dominant gene action to be important. Significant additive x additive and dominance x dominance gene interactions were found, indicating non-allelic interaction and that resistance is controlled by several genes at different loci. Using a rating scale to test for absence of epistasis indicated one locus non-allelic interaction to be negligible, but did not exclude non-allelic interaction for two o...

The evolution of pest resistance to Cry proteins threatens the long-term use of Bt crops. Busseola fusca developed resistance to Bt maize in South Africa but the mechanism of resistance is not well understood. According to the gut microbiota theory, extensive cell lysis caused by Cry proteins provide gut microbes access to the more favourable environment of the hemocoel where they germinate and reproduce, causing septicemia and death of the host. This theory brought on questions about the role of gut microbes in the efficacy of Bt maize against target lepidopteran pests. The aim of this study was to determine whether microbes present in the mid-gut of B. fusca influence the efficacy of Cry 1Ab proteins. Larvae were collected from 30 different geographical locations, dissected to excise the midgut and mid-gut content which was separated according to morphological types. The morphological types were used to test the antibiotic susceptibility of the bacteria and proved that ciprofloxacin, ampicillin and doxycycline were the most effective bacteriostatic and bactericidal antibiotics. These three antibiotics were exposed to the morphological types at different concentrations to visualise the possible deleterious effects of the antibiotics on the bacteria. This visualisation was performed by observing the growth curve of the bacteria in the presence of the combination of antibiotics. The antibiotics concentration of 500 μg/ml showed the highest efficacy compared to the other concentrations tested. An antibiotic concentration of 500 μg/ml of ciprofloxacin, ampicillin and doxycycline was incorporated into an artificial diet for the larvae to feed on for 7 days. This method was used to rid the larvae of gut microbes before allowing them to feed on Bt maize (MON810) plant material expressing Cry proteins. The results suggests that by placing antibiotic reared larvae on a Bt plant, the absence of the mid-gut microbes contributed to larvae survival on Bt maize. This observation will contribute to understanding the role of gut microbes on the efficacy of Cry proteins. MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2016 Genetically modified maize that express insecticidal proteins (Bt proteins) have been commercialized in South Africa for the control of Busseola fusca (Lepidoptera: Noctuidae). Busseola fusca has been reported to be resistant to Bt maize (Cry1Ab protein) at several localities in South Africa. Reports of pest infestation in Cry1Ab Bt maize (MON810) are regularly made in several regions, however resistance has only been confirmed in few controlled laboratory experiments. There is an urgent need to evaluate B. fusca populations in South Africa for their susceptibility to Bt maize. The aim of the study was to screen different populations of B. fusca for resistance to Bt maize and to generate baseline data regarding pest susceptibility for South Africa. Results provided an indication of the resistance status of B. fusca populations across the maize production area. Stem borer larvae were collected from 11 different field sites in and around the main maize production area of South Africa. Laboratory feeding studies with maize events expressing Cry1Ab (MON810) and Cry1A.105+Cry2Ab2 (MON89034), were conducted to compare pest fitness to that on non-Bt iso-hybrids as control. Different life-history parameters were monitored during the laboratory feeding bioassays. These were: larval survival and mass, LT50, mortality, larval duration, pupation percentage, male and female pupal mass, male and female pupal duration, sex ratio and male and female moth longevity. Large differences in susceptibility were observed between populations. Larval survival of up to 54.8% on MON810 was observed in two populations and no survival was recorded on the MON89034 event. Larval mass for some populations was significantly higher on the non-Bt iso-hybrid compared to the single-gene event. The LT50 for larvae feeding on the non-Bt maize control treatments ranged between 16-33 days compared to those on MON810 treatments with 6-25 days, and MON89034 with 4-8 days. The corrected percentage mortality for a Venda population (susceptible) was 94.16% compared to the known resistant population from Vaalharts at 0%. Larval development period on non-Bt maize was shorter compared to that on the MON810 treatment. No significant difference was observed between the non-Bt and Bt treatment in terms of the pupal mass, sex ratio or moth longevity. This study documented the levels of resistance of B. fusca and will allow us to be able to give earlywarning if this pest also evolves resistance to the pyramid events which have been launched in South Africa from 2013 onwards. Masters

Lepidopteran stem borers are among the most important pests of maize in East Africa. The objective of the present study was to predict the impact of temperature change on the distribution and abundance of the crambid Chilo partellus, the noctuid Busseola fusca, and their larval parasitoids Cotesia flavipes and Cotesia sesamiae at local scale along Kilimanjaro and Taita Hills gradients in Tanzania and Kenya, respectively. Temperature-dependent phenology models of pests and parasitoids were used in a geographic information system for mapping. The three risk indices namely establishment, generation, and activity indices were computed using current temperature data record from local weather stations and future (i.e., 2055) climatic condition based on downscaled climate change data from the AFRICLIM database. The calculations were carried out using index interpolator, a sub-module of the Insect Life Cycle Modeling (ILCYM) software. Thin plate algorithm was used for interpolation of the indices. Our study confirmed that temperature was a key factor explaining the distribution of stem borers and their natural enemies but other climatic factors and factors related to the top-down regulation of pests by parasitoids (host-parasitoid synchrony) also played a role. Results based on temperature only indicated a worsening of stem borer impact on maize production along the two East African mountain gradients studied. This was attributed to three main changes occurring simultaneously: (1) range expansion of the lowland species C. partellus in areas above 1200 m.a.s.l.; (2) increase of the number of pest generations across all altitudes, thus by 2055 damage by both pests will increase in the most productive maize zones of both transects; (3) disruption of the geographical distribution of pests and their larval parasitoids will cause an improvement of biological control at altitude below 1200 m.a.s.l. and a deterioration above 1200 m.a.s.l. The predicted increase in pest activity will significantly increase maize yield losses in all agro-ecological zones across both transects but to a much greater extent in lower areas.

Bt-maize is engineered to express insecticidal toxins derived from the bacterium Bacillus thuringiensis and has been shown to be very effective against pests like Busseola fusca. However, resistance of this pest against Bt-maize has developed and spread throughout South Africa. This study was inspired by the lack of knowledge over the microorganisms associated with the gut of these insects as they play a vital role in insect growth and development. Microbial-derived enzymes may have a role during an insect‟s adaption in different environmental conditions and to new diets. Previous studies suggest (1) that gut bacteria are required for B. thuringiensis-induced mortality in most Lepidoptera species and (2) that the toxicity of B. thuringiensis depends on microbial community interactions within the gut. The aim of this study was to determine the microbial diversity present in the midgut of B. fusca larvae occurring in maize. Busseola fusca larvae were collected from 30 sites throughout South Africa and dissected to collect their midgut contents. Serial dilutions were made of the contents and spread plated onto nutrient agar after which morphotypes were identified. One-hundred and five morphotypes were identified; DNA were extracted from the selected morphotypes and subjected to PCR analysis followed by secquencing. Sequencing results revealed the dominance of Enterococcus spp., specifically Enterococcus casseliflavus and Enterococcus gallinarum, Klebsiella spp., espesially Klebsiella pneumoniae and Klebsiella oxytoca and Bacillus spp. such as .B. thuringiensis and B. subtilis. Other organisms isolated, included Achromobacter spp., Brevudimonas spp., Caulobacter spp., Enterobacter spp., Halomonas spp., Ochrobactrum spp., Pantoea spp., Pseudomonas spp., Serratia spp., Stenotrophomonas spp., Arthrobacter spp., Brevibacterium spp., Leucobacter spp., Microbacterium spp., Planomicrobium spp. and Staphylococcus spp. The microbial diversity of larvae collected at the respective sampling sites were determined with the Shannon diversity index. The data were compared to several factors regarding the sampling sites. No significant differences were observed between the microbial diversities isolated at the respective sites. This may imply that the microbial community within B. fusca larvae are relative consistent throughout the maize production area. It is important to understand the distribution and structure of gut microbial communities within insects and whether the gut community is influenced by the geographical distribution of the insects. A better understanding of the distribution of the insects and community structure of their gut microbiota may aid in the development of better insect control strategies. MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015 The evolution of pest resistance to Cry proteins threatens the long-term use of Bt crops. Busseola fusca developed resistance to Bt maize in South Africa but the mechanism of resistance is not well understood. According to the gut microbiota theory, extensive cell lysis caused by Cry proteins provide gut microbes access to the more favourable environment of the hemocoel where they germinate and reproduce, causing septicemia and death of the host. This theory brought on questions about the role of gut microbes in the efficacy of Bt maize against target lepidopteran pests. The aim of this study was to determine whether microbes present in the mid-gut of B. fusca influence the efficacy of Cry 1Ab proteins. Larvae were collected from 30 different geographical locations, dissected to excise the mid-gut and mid-gut content which was separated according to morphological types. The morphological types were used to test the antibiotic susceptibility of the bacteria and proved that ciprofloxacin, ampicillin and doxycycline were the most effective bacteriostatic and bactericidal antibiotics. These three antibiotics were exposed to the morphological types at different concentrations to visualise the possible deleterious effects of the antibiotics on the bacteria. This visualisation was performed by observing the growth curve of the bacteria in the presence of the combination of antibiotics. The antibiotics concentration of 500 μg/ml showed the highest efficacy compared to the other concentrations tested. An antibiotic concentration of 500 μg/ml of ciprofloxacin, ampicillin and doxycycline was incorporated into an artificial diet for the larvae to feed on for 7 days. This method was used to rid the larvae of gut microbes before allowing them to feed on Bt maize (MON810) plant material expressing Cry proteins. The results suggests that by placing antibiotic reared larvae on a Bt plant, the absence of the mid-gut microbes contributed to larvae survival on Bt maize. This observation will contribute to understanding the role of gut microbes on the efficacy of Cry proteins. Masters

The evolution of resistance to Bacillus thuringiensis (Bt) maize by the African stem borer, Busseola fusca, in South Africa highlighted the importance of the development of appropriate integrated resistance management (IRM) strategies for stem borers in Africa. Landscape heterogeneity is characteristic of African agroecosystems. This heterogeneity, in addition to between field and within-field spatial mosaics resulting from variable gene expression in Bt maize, will provide challenges to managing resistance evolution of the lepidopteran stem borers that attack maize. Adding to this landscape heterogeneity is the cultivation of open-pollinated maize varieties (OPVs) and bimodal rainfall patterns that allow two maize cropping seasons each year in many subtropical and tropical areas. The role that these factors, as well as aspects such as low-dose expression events, refuge compliance, the genetic bases of resistance, pest behaviour, host plant range and farming practices, may play in the evolution of stem borers to Bt maize in Africa are addressed in this chapter.

International audience; In Lepidoptera, host plant selection is first conditioned by oviposition site preference of adult females followed by feeding site preference of larvae. Dietary experience to plant volatile cues can induce larval and adult host plant preference. We investigated how the parent's and self-experience induce host preference in adult females and larvae of three lepidopteran stem borer species with different host plant ranges, namely the polyphagous Sesamia nonagrioides, the oligophagous Busseola fusca and the monophagous Busseola nairobica, and whether this induction can be linked to a neurophysiological phenotypic plasticity. The three species were conditioned to artificial diet enriched with vanillin from the neonate larvae to the adult stage during two generations. Thereafter, two-choice tests on both larvae and adults using a Y-tube olfactometer and electrophysiological (electroantennography [EAG] recordings) experiments on adults were carried out. In the polyphagous species, the induction of preference for a new olfactory cue (vanillin) by females and 3rd instar larvae was determined by parents' and self-experiences, without any modification of the sensitivity of the females antennae. No preference induction was found in the oligophagous and monophagous species. Our results suggest that lepidopteran stem borers may acquire preferences for new olfactory cues from the larval to the adult stage as described by Hopkins' host selection principle (HHSP), neo-Hopkins' principle, and the concept of 'chemical legacy.'

MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015 Busseola fusca is an indigenous lepidopteran pest species in tropical Africa, attacking several grain crops. Crop loss caused by this pest can be as high as 100% depending on conditions. Despite it being a major pest in Africa, occurring in contrasting climatic zones, only a few studies have been published on its developmental biology. The effect of temperature on the development of B. fusca was studied at five different temperature regimes namely 15, 18, 20, 26 and 30 ± 1 °C and 70 ± 30 % relative humidity (RH) with 14L: 10D photoperiod. The number of instars for B. fusca was also determined. The most favourable temperature as well as the upper threshold temperature for larval development was found to be between 26 and 30 °C. Total development period was 152.6 to 52.6 days, respectively, at 15°C, and 26 - 30°C. The thermal constants for B. fusca was 99.50, 536.48, 246.25 and 893.66°D and lower temperature threshold was 10.36, 8.14, 8.99 and 8.84°C, for completion of the egg, larval, pupal, and egg-to-adult stages, respectively. The number of larval instars was determined by using head capsule widths that ranged from 0.31 - 2.68 mm. Clear distinctions of head capsule widths could be made from instar 1 to 3, yet overlapping occurred from instar 4 to 6. No distinction could be made between instars 7 and 8 in terms of head capsule width. All successive instars, except for instar eight, increased in size according to Dyar’s ratio. The effect of temperature on reproduction of B. fusca was studied at 15, 20, 26 and 30 ± 1°C, 70 ± 30% RH with 14L: 10D photoperiod. Oviposition occurred at all the temperatures evaluated, but no fertility was recorded at 30°C. The total number of eggs laid by B. fusca females was 300 - 400 eggs and the optimum temperature for oviposition and fertility was determined to be between 20 and 26°C. Results from this study on the thermal constants and lower and upper threshold temperatures of B. fusca can be used to predict the impact of climate change on the distribution and population growth of this pest. Masters

MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015 Bt-maize is engineered to express insecticidal toxins derived from the bacterium Bacillus thuringiensis and has been shown to be very effective against pests like Busseola fusca.However, resistance of this pest against Bt-maize has developed and spread throughout South Africa. This study was inspired by the lack of knowledge over the microorganisms associated with the gut of these insects as they play a vital role in insect growth and development. Microbial-derived enzymes may have a role during an insect's adaption in different environmental conditions and to new diets. Previous studies suggest (1) that gut bacteria are required for B. thuringiensis-induced mortality in most Lepidoptera species and (2) that the toxicity of B. thuringiensis depends on microbial community interactions within the gut. The aim of this study was to determine the microbial diversity present in the midgut of B. fusca larvae occurring in maize. Busseola fusca larvae were collected from 30 sites throughout South Africa and dissected to collect their midgut contents. Serial dilutions were made of the contents and spread plated onto nutrient agar after which morphotypes were identified. One-hundred and five morphotypes were identified; DNA were extracted from the selected morphotypes and subjected to PCR analysis followed by secquencing. Sequencing results revealed the dominance of Enterococcus spp., specifically Enterococcus casseliflavus and Enterococcus gallinarum, Klebsiella spp., espesially Klebsiella pneumoniae and Klebsiella oxytoca and Bacillus spp. such as .B. thuringiensis and B. subtilis. Other organisms isolated, included Achromobacter spp., Brevudimonas spp., Caulobacter spp., Enterobacter spp., Halomonas spp., Ochrobactrum spp., Pantoea spp., Pseudomonas spp., Serratia spp., Stenotrophomonas spp., Arthrobacter spp., Brevibacterium spp., Leucobacter spp., Microbacterium spp., Planomicrobium spp. and Staphylococcus spp. The microbial diversity of larvae collected at the respective sampling sites were determined with the Shannon diversity index. The data were compared to several factors regarding the sampling sites. No significant differences were observed between the microbial diversities isolated at the respective sites. This may imply that the microbial community within B. fusca larvae are relative consistent throughout the maize production area. It is important to understand the distribution and structure of gut microbial communities within insects and whether the gut community is influenced by the geographical distribution of the insects. A better understanding of the distribution of the insects and community structure of their gut microbiota may aid in the development of better insect control strategies. Masters

The present study was conducted to determine the comparative efficacy and bioactivity of aqueous extracts of four botanicals (leaf, root bark, flower) under in vitro condition. Cypermethrin 1% G was used as standard check and untreated control against maize stem borer in maize (Zea mays L.), during 2012 at Ambo Plant Protection Research Center, Ethiopia. The treatments were aqueous leaf extract of Nicotiana spp. L. and Cymbopogon citratus, root bark aqueous extract of Securidaca longepedunculata F., and flower extract of Chrysanthemum cinerariaefolium at 5% concentration. The cumulative data revealed that the standard check-Cypermethrin 1% G at rate of 0.3 kg/ hectare recorded significantly higher mean percent mortality of maize stem borer, Busseola fusca, over all the other treatments. Among the botanical extracts, C. cinerariaefolium and C. citrates 5% concentration was recorded higher efficacy mean mortality (75 and 58.33), respectively, against B. fusca within three days, and found to be at par with some of the other botanical extracts. The Nicotiana spp. leaf extracts and S. longepedunculata root bark extract showed significantly lower efficacy mean mortality.

Busseola fusca is an indigenous lepidopteran pest species in tropical Africa, attacking several grain crops. Crop loss caused by this pest can be as high as 100 % depending on conditions. Despite it being a major pest in Africa, occurring in contrasting climatic zones, only a few studies have been published on its developmental biology. The effect of temperature on the development of B. fusca was studied at five different temperature regimes namely 15, 18, 20, 26 and 30 ± 1 °C and 70 ± 30 % relative humidity (RH) with 14L: 10D photoperiod. The number of instars for B. fusca was also determined. The most favourable temperature as well as the upper threshold temperature for larval development was found to be between 26 and 30 °C. Total development period was 152.6 to 52.6 days, respectively, at 15 °C, and 26 - 30 °C. The thermal constants for B. fusca was 99.50, 536.48, 246.25 and 893.66 °D and lower temperature threshold was 10.36, 8.14, 8.99 and 8.84 °C, for completion of the egg, larval, pupal, and egg-to-adult stages, respectively. The number of larval instars was determined by using head capsule widths that ranged from 0.31 - 2.68 mm. Clear distinctions of head capsule widths could be made from instar 1 to 3, yet overlapping occurred from instar 4 to 6. No distinction could be made between instars 7 and 8 in terms of head capsule width. All successive instars, except for instar eight, increased in size according to Dyar’s ratio. The effect of temperature on reproduction of B. fusca was studied at 15, 20, 26 and 30 ± 1 °C, 70 ± 30 % RH with 14L: 10D photoperiod. Oviposition occurred at all the temperatures evaluated, but no fertility was recorded at 30 °C. The total number of eggs laid by B. fusca females was 300 - 400 eggs and the optimum temperature for oviposition and fertility was determined to be between 20 and 26 °C. Results from this study on the thermal constants and lower and upper threshold temperatures of B. fusca can be used to predict the impact of climate change on the distribution and population growth of this pest. MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

Sites in the humid forest of Cameroon and the derived savanna of Benin were selected to evaluate the effect of planting border rows of wild host plants on lepidopterous stem-borer infestations and on maize yield. Grass species were chosen that in surveys and greenhouse trials were highly attractive to ovipositing female moths but with offspring mortality of close to 100%, thus acting as trap plants. In Cameroon, elephant grass Pennisetum purpureum Moench significantly lowered infestations of Busseola fusca (Fuller), Sesamia calamistis Hampson and Eldana saccharina Walker and increased yields of maize though the differences were not significant during all three cropping seasons. In 1998 in Benin, the only grass tested, Pennisetum polystachion L., significantly increased parasitism of mainly S. calamistis eggs by Telenomus spp. and larvae by Cotesia sesamiae Cameron and reduced numbers of the cob-borer Mussidia nigrivenella Ragonot. In 1999, three grass species; P. polystachion, Sorghum arundinaceum (Desv.) Stapf and Panicum maximum Jacq. were tested. Panicum maximum was the most efficient species for suppressing S. calamistis and M. nigrivenella infestations and enhancing egg and larval parasitism. In the Benin trials, with the exception of M. nigrivenella damage to cobs, the grass species tested had no beneficial effect on yield because pest densities were too low and also rodent damage to maize was enhanced with grasses in the vicinity of the crop. By contrast, stand losses due to Fusarium verticillioides Sacc. (Nirenberg), were significantly reduced by border rows of grasses.

The suitability of two New World pyralids Diatraea saccharalis and D. grandiosella for development of a South African population of the Old World braconid Cotesia sesamiae was studied for over 30 generations. These host–parasitoid combinations are novel associations. The C. sesamiae population was collected from Busseola fusca, reared for four generations on the novel host Chilo partellus, and for one generation in quarantine on another novel host D. saccharalis. Subsequent parasitoid generations were used for experiments. D. saccharalis was completely suitable, whereas D. grandiosella was only a marginally suitable host. Total numbers of parasitoid progeny that emerged from D. saccharalis increased over the first 13 generations, then declined by the 30th generation. Development time for C. sesamiae from egg to cocoon formation averaged 14.5–16.0 days and did not vary over time. D. grandiosella often encapsulated the parasitoid progeny, which did not decrease after rearing for multiple generations on Diatraea. Results suggest that before releasing a novel-association parasitoid into the field, there may be a benefit of rearing a parasitoid species on the target pest first; however, this benefit may be transient.

Many braconid wasp species inject polydnaviruses to overcome their host's immune system. In the species Cotesia sesamiae, two biotypes exist that differ in their ability to develop in the host Busseola fusca. The biotype from coastal Kenya is infected with Wolbachia and is not able to develop in larvae of B. fusca, whereas the uninfected inland biotype of this wasp can develop in B. fusca. The genetic transmission of the developmental ability was studied through a series of genetic crosses and superparasitization experiments. The Wolbachia infection of the coastal type did not play a role in the encapsulation response of the host. Experiments show that the polydnaviruses of the wasps could not prevent the encapsulation of the coastal parasitoid eggs. Most likely, larval characteristics such as surface proteins played a more important role in the encapsulation response of the host even in the presence of a functional polydnavirus.

An insecticide exclusion method was used to evaluate the effect of parasitoids on level of infestation by the stem borers, Busseola fusca (Fuller) and Chilo partellus (Swinhoe), in grain sorghum. In field trials conducted at Brits and at Delmas, South Africa, a selective organophosphate insecticide, dimethoate, was applied twice weekly at each site to three subplots whereas three other identical subplots served as controls. Twelve plants were randomly selected from each subplot at weekly intervals and removed from the field. In the laboratory all plants were dissected to record borer infestation. In order to determine parasitism levels egg batches were kept in Petri dishes and all borer larvae and pupae were kept individually in vials until either parasitoids or moths emerged. At Brits ca. 97% of borers were C. partellus and 3% B. fusca, whereas at Delmas 37.5% were C. partellus and 62.5% B. fusca. The most abundant parasitoids of B. fusca were Cotesia sesamiae (Cameron) and Bracon sesamiae Cameron. The dominant parasitoids of C. partellus at both sites were C. sesamiae, Stenobracon spec., Dentichasmias busseolae Henrich and Pediobius furvus (Gahan). No egg parasitoids were found. At both sites, infestation levels in the sprayed plots were significantly higher than in the untreated plots. On the other hand, parasitism levels of borers in the unsprayed plots were significantly higher than in the treated plots. It was concluded that the higher infestation level of sorghum by stem borers in the sprayed plots was because of partial elimination of parasitoids and possibly other natural enemies by the pesticide.

Host preference of the stem borer Busseola fusca (Fuller) was studied in laboratory and field conditions at Halhale and Halhal Begos, Eritrea from 1997 to 1999, using nine cultivated and wild plants. Sudan grass (Sorghum vulgare Pers. var. sudanense) had the highest infestation (91%) and was also the most preferred host for oviposition. The highest larval density was on maize followed by sorghum. Pearl millet, finger millet, setaria and wheat had a lower infestation and larval feeding preference. The possible use of sudan grass as a trap crop for B. fusca is discussed.

▪ Abstract Cereals (maize, sorghum, millet, rice) are extremely important crops grown in Africa for human consumption. Of the various insect pests attacking cereal crops in Africa, lepidopteran stem borers are by far the most injurious. All 21 economically important stem borers of cultivated grasses in Africa are indigenous except Chilo partellus, which invaded the continent from India, and C. sacchariphagus, which has recently been found in sugarcane in Mozambique. C. partellus is competitively displacing indigenous stem borers in East and southern Africa. A parasitoid, Cotesia flavipes, was introduced from Pakistan for biological control of C. partellus and caused a 32–55% decrease in stem borer densities. This article is an attempt to summarize the status of knowledge about economically important cereal stem borers in Africa with emphasis on their distribution, pest status and yield losses, diapause, natural enemies, cultural control, host plant resistance, and biological control. Special attention is given to Busseola fusca and C. partellus, the most important pests of maize and grain sorghum.

Stemborers of maize and their associated indigenous parasitoids were studied at Katumani, Kiboko and Ithookwe in the semi-arid areas of eastern Kenya over a period of four seasons (short rains, 1996—long rains, 1998). Maize fields established at each site were sampled at least weekly up to plant maturity, and all the stemborer life stages recovered were reared individually in the laboratory for possible parasitoid emergence. The stemborers that attacked maize at the three sites were Chilo partellus, the dominant and most widespread stemborer, Sesamia calamistis, Cryptophlebia leucotretci and Busseola fusca. A complex of 22 mainly larval parasitoids attacked the stemborers, but the parasitism was generally low. C. partellus was the most frequently parasitized stemborer. The most widespread larval parasitoid was Cotesia sesamiae, followed by Chelonus curvimaculatus, while Dentichasmias busseolae and Pediobius furvus were the most common pupal parasitoids. The low percentage parasitism by indigenous...

The aim was to identify biological and physical factors responsible for reducing maize yield in Cameroon. Two surveys were conducted in 137 fields in two agroecological zones in 1995–1997. In the Humid Forest (HF), Bipolaris maydis, Stenocarpella macrospora, Puccinia polysora, Rhizoctonia solani and soil fertility were factors that reduced maize production in 1995 and 1996. In the Western Highlands (WHL), Cercospora zeae-maydis, and the interaction between soil fertility and maize variety were the most important constraints to maize production in 1996. In 1997, C. zeae-maydis, S. macrospora, physiological spot and stem borer damage (Busseola fusca) were negatively related to ear weight. The combination of these biological factors (diseases and insects), and the physical parameter of soil fertility were responsible for reducing maize yield in these selected benchmarks of Cameroon. Maximum potential yield reductions were estimated at 68% due to B. maydis and 46% due to S. macrospora, respectively, in the HF in 1995. In 1996, maximum potential yield reductions in the HF were estimated at 34%, 41% and 30% due to S. macrospora, P. polysora and R. solani, respectively. In the WHL, C. zeae-maydis had the potential to cause a yield reduction of 79% in 1996. In the WHL in 1997, the interaction between C. zeae-maydis and B. fusca, stem diseases and the physiological spot caused potential reductions of 52%, 34% and 39%, respectively.

The effect of indirect exposure to Cry 1Ab proteins on the biology of the green Lacewing (Chrysoperla Pudica) Genetically modified (GM) maize that expresses Cry1Ab protein was developed for control of the maize stem borer (Busseola fusca). In this study we evaluated the possible effect of this protein on the non-target organism Chrysoperla pudica, by feeding it with resistant larvae of the target pest. Only a small number of adverse effects were observed on the biology of C. pudica.

A PCR detection method for mutations in receptor protein genes from Busseola fusca midgut material potentially involved in Bt-resistance Busseola fusca (Fuller) (Lepidoptera: Noctuidae) is a major insect pest to Bt-maize in South Africa. No study has yet been done to determine the molecular mechanism of B. fusca resistance to Cry1Ab. Aminopeptidase N (1-6), cadherin and alkaline phosphatase receptor-protein genes were amplified and sequences of PCR products were determined. BLAST searches showed similarity to the respective receptor-protein genes. Mutations can thus be identified by comparing sequences of receptor-protein genes from resistant and susceptible larvae.

A PCR generation method for receptor-protein genes from Busseola fusca midgut material potentially involved in Bt-resistance. No study has been done to determine the molecular mechanism of Busseola fusca, a major insect pest in South Africa, resistance to Cry1Ab. Receptor-protein genes were amplified and sequenced. BLAST searches showed similarity to receptor-protein genes.

Surveys of the cereal stemborers and their natural enemies in Zambia were initiated in 1997. The surveys verified the presence of three stemborer species on maize, sorghum and pearl millet. These were the maize stalk borer, Busseola fusca Fuller (Lepidoptera: Noctuidae), the spotted stemborer, Chilo Partellus (Swinhoe) (Lepidoptera: Crambidae) and the African pink borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae). Occasionally, the sugarcane borer, Eldana saccharina Walker (Lepidoptera: Pyralidae) was also recovered especially around areas near the sugarcane plantation at Mazabuka, Southern province. Chilo Partellus was the predominant stemborer in region 1 (areas with less than 600 mm of rainfall per annum). Three ‘hot spot’ areas, namely Luangwa, Buleya Malima and Kalobolelwa, were identified based on the abundance of Ch. partellus. The exotic parasitoid, Cotesia flavipes Cameron (Hymenoptera: Braconidae) was released in the three areas for the control of Ch. partellus. However, post-release surveys in these areas have not revealed any recoveries of Co. flavipes. Three indigenous natural enemies, namely Cotesia sp., Dentichasmias sp. and Dolichogenidea sp. emerged from the field-collected larvae.

The stemborers Busseola fusca (Fuller) and Chilo Partellus (Swinhoe) cause the highest economic damage to maize and sorghum in Zimbabwe. A number of studies on stemborer bioecology and management in Zimbabwe have been conducted, but most are still incomplete. The more important of these are studies on life history, incidence and distribution patterns, host plants, yield losses, chemical control, cultural control, host plant resistance, the use of sex pheromones, and biological control. These are discussed here in detail, and areas where further research is needed are pointed out. As part of an integrated strategy for managing stemborers in Zimbabwe, an exotic braconid larval parasitoid, Cotesia flavipes Cameron, has been released in the lowveld area and prospects for its establishment appear to be good. However, this establishment might be curtailed mainly by the inability of Co. flavipes to adapt to the seasonal carryover mechanisms utilised by the indigenous Cotesia sesamiae (Cameron).

A study was conducted at Katumani, Kiboko and Ithookwe, in the semi-arid Eastern Province of Kenya for four seasons (short rains 1996-long rains 1998), to confirm the major stemborers of maize, and to introduce and monitor the colonisation of Cotesia flavipes Cameron (Hymenoptera: Braconidae) in these stemborers. About 6750 adults of Cotesia flavipes were released at each site, from ‘release stations’, starting one week after plant emergence and repeated fortnightly up to harvest. Pre-release parasitism of the stemborers was determined, for two seasons prior to release of Co. flavipes, during the season of release and one season after the release of this parasitoid. Parasitism was assessed from developmental stages of the stemborers recovered through destructive sampling of 100 plants, starting one week after plant emergence. This was repeated weekly at Katumani, and fortnightly at Kiboko and Ithookwe until harvest. The stemborers recovered from maize were Chilo partellus, Sesamia calamistis, Cryptophlebia leucotreta and Busseola fusca in descending order of abundance, with Ch. partellus being the most widespread stemborer. Cotesia flavipes parasitised and successfully colonised Ch. partellus and S. calamistis in the three sites during the season of release and one season post-release of the parasitoid. Parasitism by Co. flavipes ranged from 7.14-25.80 %. The colonisation rate of Co. flavipes in the two major stemborers in the semi-arid Eastern Province of Kenya suggests the high potential of this parasitoid in regulating populations of stemborers that attack maize in this region.

A survey was conducted in the four regions of Tanga, Morogoro, Coast and Dar es Salaam in eastern Tanzania to determine the distribution and species composition of cereal stemborers and their natural enemies. A total of 22 fields were sampled in Tanga, 28 in Morogoro, 17 in Coast and one in Dar es Salaam. Chilo partellus was found to be the predominant species, accounting for 80 % of all stemborers collected. Busseola fusca, Sesamia calamistis and Chilo orichalcociliellus made up 15,4 and less than 1 % of the stemborers collected respectively. Infestation levels varied with the age of the plants, whereby younger plants were more severely infested (infestation ranging from 20–40 %) than mature plants (infestation ranging from 5–15 %). Two larval parasitoids, Cotesia sesamiae and Cotesia flavipes, were the main natural enemies collected. However, the levels of parasitism of the stemborers were very low. The exotic natural enemy Co. flavipes may have spread from the Kenya coast (where it is established) into eastern Tanzania.

Three hundred and ninety-two maize fields in the southern arable zone of Kenya were sampled for lepidopteran cereal stemborers from 1996–2000. Chilo partellus (Swinhoe) was the most abundant stemborer, and was found at all locations with elevations below 1500 m, and at some locations between 1500 and 2300 m. The highest density of C. partellus was in the semi-arid ecological zone of eastern Kenya. Chilo orichalcociliellus (Strand) was found in the lowland southern coastal area, and a few inland sites on the border of Tanzania in southeastern Kenya. Busseola fusca Fuller was dominant in highland areas. In the Lake Victoria Basin, which has an elevation of about 1100 m, B. fusca was dominant at some sites, but overall, C. partellus was more abundant. Sesamia calamistis Hampson was present at all elevations and all locations, but typically at low densities. Eldana saccharina (Walker) was found in two-thirds of the fields sampled in the Lake Victoria Basin. These results are compared with the distributions of the various stemborers in the 1950s to 1960s, as reported in the literature.

Chilo Partellus (Swinhoe) was first recorded in South Africa in 1958 and became a major pest of maize and grain sorghum. It has invaded the main maize producing areas in the Highveld Region, gradually competitively displacing the indigenous Busseola fusca (Fuller). Between 1980 and 1993 two egg, seven larval and two pupal parasitoids were introduced for biological control of Ch. partellus. Cotesiaflavipes Cameron (Braconidae), Paratheresia claripalpis van der Wulp (Tachinidae), Tetrastichus howardi (Olliff) (Eulophidae) and Xanthopimpla stemmator Thunberg (Ichneumonidae) were released and recovered from the field. Recoveries were made up to a few weeks after releases but parasitoids failed to survive the winter and establish. The harsh winter conditions in the release sites, the long larval diapause period of Ch. partellus, lack of synchronisation between the development of the parasitoids and that of their host larvae, and absence of alternative host plants were identified-as the main obstacles for the parasitoids establishment. It is concluded that the prospects of achieving any degree of biological control of stemborers in the Highveld Region with parasitoids from the tropics are poor. A parasitoid from a temperate zone of the USA, Macrocentrus granali Goidanich (Braconidae), was introduced recently into South Africa and is currently reared on Ch. partellus in quarantine. Macrocentrus granali stays dormant in its diapausing host, Ostrinia nubilalis (Hubner), during winter to emerge in spring. Because of its ability to diapause in winter it is hoped that after releases, M. granali will establish on Ch. partellus in the Highveld Region of South Africa.

The most common lepidopterous borers attacking maize and/or the wild host Pennisetum purpureum in the forest zone of Cameroon are the noctuids Busseola fusca (Fuller), Sesamia calamistis (Hampson) and Poeonoma serrata (Hampson), the pyralids Eldana saccharina (Walker) and Mussidia nigrivenella (Ragonot), and Cryptophlebia leucotreta (Tortricidae). The within-plant distribution on maize and elephant grass was studied for the predominant species B. fusca, and on maize only for E. saccharina to determine the basic sampling unit. On both plant species, B. fusca showed a strong oviposition preference for young plant parts. By contrast, E. saccharina larvae and pupae on maize were only found on older plant parts indicating that it does not oviposit on young plants. No part of the plant strata appeared to be a stable sampling unit and it is recommended to carry out whole plant or whole tiller sampling for maize and grass, respectively. For the development of sampling plans, dispersion was described for all species using Taylor’s power law and a non-linear model which gives the relationship between the proportion of infested plants [P(I)] and mean density (m). Busseola fusca egg batches as well as diapausing larvae and pupae on maize showed a random distribution whereas all the other cases were aggregated, with B. fusca egg batches on elephant grass exhibiting the lowest and M. nigrivenella on maize the highest aggregation. Optimal sample size/mean density curves were developed for groups of insects with low and high aggregation.

The stemborers Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Crambidae) are important pests of maize and sorghum in South Africa. A habitat management system for these pests is being developed in the Northern Province of South Africa. This management system is similar to the one used in eastern Africa, where host and non-host plants of stemborers are used to repel moths away from the main crop and attract them to highly attractive trap plants. To identify possible trap crops, a survey of wild host plants of stemborers was undertaken in the Northern Province of South Africa and several new host plants were recorded. As a possible trap crop for stemborers, various Napier grass (Pennisetum purpureum) varieties were evaluated for oviposition preference by Ch. partellus moths and subsequent larval survival on those varieties. Few larvae survived longer than 15 days after inoculation onto Napier grass plants. A survey was conducted of farming practices that would affect the adoption of habitat management strategies. The high usage of tractors for ploughing may have a negative effect on adoption of perennial intercrops in a habitat management system. The common practice of free grazing animals also reduced the fodder value and benefit of trap crops. The value of Napier grass does not only lie in its use as trap crop but also as a measure to limit soil erosion and as animal feed.

Studies were conducted in two districts of eastern Uganda from 1997 to 1999 to introduce and monitor the establishment of an exotic parasitoid, Cotesia flavipes Cameron (Hymenoptera: Braconidae), for the control of the stemborer Chilo Partellus (Swinhoe) (Lepidoptera: Pyralidae), and also to determine the stemborer species complex in maize and sorghum. The study confirmed the presence of four important stemborers, two pyralids Ch. partellus and Eldana saccharina Walker and two noctuids, Busseola fusca Fuller and Sesamia calamistis Hampson. Chilo Partellus was dominant, constituting 53-88% of stemborers fourd followed by B. fusca at 8–37 %. The most abundant local parasitoid was the larval parasitoid Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae). The pupal parasitoids Pediobius furvus Gahan (Hymenoptera: Eulophidae) and Dentichasmias busseolae Heinrich (Hymenoptera: Ichneumonidae) were also recorded. Parasitism of Co. sesamiae on Ch. partellus ranged between 0 and 13.1 %. The introduced Co. flavipes was recovered from all sites in four consecutive seasons (between 1998 and 1999) causing parasitism of between 4 and 32.9 % on Ch. partellus. Cotesia flavipes was also recovered from the indigenous stemborers B. fusca and S. calamistis. This study indicates that Co. flavipes has established in eastern Uganda.

Surveys were conducted to determine the species composition of stemborers and their natural enemies in maize and sorghum in 1999 and 2000 in eastern, northern, southern and western Ethiopia. The six species of stemborers found attacking maize and sorghum were Chilo Partellus (Swinhoe) (Lepidoptera: Crambidae), Busseolafiisca Fuller, Sesamia calamistis Hampson (Lepidoptera: Noctuidae), S. nonagrioides botanephaga Tarns & Bowden (Lepidoptera: Noctuidae), Rhynchaenus niger (Horn) (Coleoptera: Rhynchophoridae) and Pissodes dubious (Strom) (Coleoptera: Rhynchophoridae). Twenty species of primary parasitoids of eggs, larvae and pupae of Ch. partellus, B. fusca and S. calamistis were recorded. Other natural enemies, including predators, fungi and nematodes, were also found. Cotesia flavipes Cameron (Hymenoptera: Braconidae) was the dominant and the most widely distributed parasitoid of stemborers in Ethiopia, and was reared from field-collected Ch. partellus, B. fusca and S. calamistis.

Field surveys carried out in Mozambique showed that two indigenous cereal stemborers, Busseola fusca Fuller (Lepidoptera: Noctuidae), Sesamia calamistis Hampson (Lepidoptera: Noctuidae) and one exotic stemborer, Chilo parteltus (Swinhoe) (Lepidoptera: Pyralidae), are the main pests of maize and sorghum in the country. Busseola fusca was abundant at high altitudes (> 800 m) and Ch. partellus was abundant at low altitudes (< 800 m). Sesamia calamistis occurred at all elevations but in low numbers. Of the three stemborers, Ch. partellus was the most widespread and abundant pest of maize followed by B. fitsca. Therefore, a programme was initiated to introduce the exotic parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) to increase natural suppression of Ch. partellus populations. Cotesia flavipes was introduced into southern Mozambique for the first time in November 1996. Additional releases were subsequently carried out in several places in southern and central Mozambique from 1998–2000. The parasitoid was recovered from all localities sampled 1 to 3 years after its introduction, indicating that this exotic parasitoid had established in the southern and central regions of Mozambique.

The feeding ecology of the Southern Bold Ibis, Geronticus calvus, was studied in the Free State Province, South Africa, during two breeding seasons in 1994 and 1996. Fields of harvested maize, burnt grass and overgrazed pastures are the main feeding habitats of the birds in this region throughout the breeding season. The ibises forage mainly in flocks ranging from 2 to 24 birds (x = 5), often in association with cattle and other animals. Analysis of stomach contents, pellet contents and food remnants revealed that larvae of Busseola fusca (Lepidoptera: Noctuidae) and imagos of Coleoptera constitute the staple food. These larvae were collected from maize stalks trampled by cattle, while Coleoptera were collected mainly from dung, grass clumps and from the ground in pastures. A considerable amount of inorganic matter, such as pieces of glass, porcelain, plastic, metal, buttons and gravel, was also found.

This study focused on the suitability of four species of cereal stem borers for the development of five geographic populations of Cotesia sesamiae (Cameron). C. sesamiae, an indigenous larval parasitoid of gramineous stem borers, is widespread in Africa. Four stem borers, Chilo partellus (Swinhoe), Chilo orichalcociliellus Strand (Lepidoptera: Crambidae), Busseola fusca Fuller, and Sesamia calamistis Hampson (Lepidoptera: Noctuidae), were offered to C. sesamiae for oviposition. Parasitoid individuals originated from five locations in Kenya. Biological parameters such as developmental time, percentage parasitism, progeny production, mortality of immature parasitoids, and proportion of female progeny were compared across host species. The two populations from western Kenya developed well on B. fusca. However, populations from the coast and the Eastern Province could not successfully parasitize B. fusca. With the exception of B. fusca, the percentage of hosts successfully parasitized by the different C. sesamiae populations was not different. The size of the host appeared to be an important factor influencing the development and reproductive potential of the parasitoid. We conclude that the different parasitoid populations were adapted to location-specific characteristics. Parasitoid–host compatibility must be evaluated before release for better establishment and colonization.

Busseola fusca (Fuller) is one of the most important pest of cereals in sub-Saharan Africa. Cotesia sesamiae (Cameron) is the predominant parasitoid attacking B. fusca larvae in many parts of Africa. An exotic parasitoid, Cotesia flavipes Cameron, was introduced into Kenya in 1993 for the control of Chilo partellus (Swinhoe). Laboratory studies indicated that although C. flavipes would search for, and attack B. fusca , it was not able to complete its development in this host. The aim of the present study was to investigate the outcome of multiple parasitism of B. fusca by the two Cotesia species. The study showed that when both parasitoid species stung a B. fusca larva at the same time, both parasitoids emerged from more than half of the host larvae, C. flavipes alone emerged from 17%, and C. sesamiae alone emerged from 9%. When the larvae were parasitized by C. sesamiae first, and then 2 h later by C. flavipes , and vice versa, most of the progeny were C. flavipes . However, when B. fusca larvae were stu...

This study aimed at an assessment of the potential of the egg parasitoid Telenomus isis (Polaszek) as a biological control agent of cereal stem borers. Therefore, the effects of temperature, host species, host age, and time of host deprivation on the development and the reproductive potential of T. isis were studied in the laboratory. By use of linear regression and a modified Logan model and with eggs of the noctuid Sesamia calamistis Hampson as hosts, the lower and upper thresholds for development were estimated at 13.1 and 36°C, respectively, and the optimal temperature for development was 31°C. Female T. isis had no measurable preoviposition period, and the oviposition period ranged from 3 to 5 days. Approximately 66% of the total lifetime complement of eggs of T. isis were produced within 6 h after emergence. Average total lifetime fecundity was 61.1 and 82.1 eggs per female at 21 and 28°C, respectively. Longevity of adult females was 17.1 days at 21°C and 5.2 days at 30°C. Host acceptance and suitability were tested, using nine lepidopteran borer species. Only the noctuids S. calamistis, Sesamia poephaga (Tam & Bowden), Sesamia botanephaga (Tam & Bowden), and Busseola fusca (Fuller) were successfully attacked by T. isis. Parasitism and emergence did not differ among those species, but the sex ratio (expressed as proportion of female progeny) was significantly lower on S. calamistis. An increase of the host age from 1 to 4 days significantly reduced mean parasitism from 56.7 to 23.5%. Parasitoid emergence rates and sex ratio did not vary among 1-, 2-, or 3-day-old host eggs, but both parameters were significantly lower on 4-day-old eggs. With increasing duration of host deprivation from 0 to 17 days, longevity increased from 8.5 to 18.5 days, whereas average lifetime fecundity decreased from 81.2 to 40.5 eggs per female, respectively, indicating resorption of eggs. The results are discussed and compared with life table parameters of the ubiquitous egg parasitoid Telenomus busseolae (Gahan).

A survey of lepidopterous stem borers attacking sorghum, maize and pearl millet was done in Eritrea during the cropping seasons of 1996 and 1997. The survey area covered the highlands, western and eastern lowlands and the coastal region of the Red Sea, where sorghum, maize and millet are the major crops. Four lepidopterous stem borers species, namely Busseola fusca Fuller, Chilo partellus Swinhoe, Sesamia calamistis Hampson and Chilo orichalcociliellus Strand were found attacking these crops. B. fusca in the highlands and C. partellus in the lowlands were the major pests of these crops in Eritrea. Two predators and four parasitoids were recorded as natural enemies of the stem borers. The population of the natural enemies was low with 9–20% parasitism. Nineteen cultivated and wild plants were identified as host plants of the stem borers of which sudan grass, elephant grass and hyparrhenia were found with high numbers of stem borer larvae. The pests were able to survive from one season to another and during the dry periods as diapausing larvae on crop residues, maize grown under irrigation and on wild host plants mainly grown in forest enclosure areas.

During the 1998/99 season considerable stem damage was caused by B. fusca in commercial plantings of Bt-maize, without leaf feeding damage during the vegetative stages of plant development. This indicated that larvae may survive on some less toxic plant part subsequent to the vegetative stages. In this study a laboratory bioassay was conducted, using forced feeding of larvae on various parts of Bt-maize. In a field trial larval survival and plant damage were recorded following artificial infestation of Bt- plants one week before, and one and three weeks after tasseling. It appears that there is a window of approximately 14 days immediately preceding tasseling, in which relatively late infestations may result in increased larval survival, due to the availability of silks as a primary food source to neonate larvae. The Bt-protein concentration in silks appears to be low enough to allow survival of some larvae until completion of the first two instars, after which the ear tips and husk leaves serve as import...

The influence of sowing date and fertilizer application on the incidence anddamage ofthe maize stemborer (Busseolafusca Fuller) in sorghum(Sorghumbicolor L.) was investigated at the Halhale Research Centre in Eritrea during 1997 - 99. The trials were conducted in a splitplot design with sowing date as the main plot and fertilizer as subplots. There were six sowing dates at an interval of 15 days starting fromearly April tomid-June. There were fertilized and unfertilized subplots. Data on larval count, per cent infestation, per cent deadheart, heading and maturity dates, plant height and yield were recorded for each plot. Fertilizer had no effect on the incidence and damage of the stem borer (B. fusca). There was no interaction between fertilizer and sowing dates on the larval population and damage by stem borers. Sowing date had a significant effect on stem borer incidence and damage levels. Early sowing dates (April 1 and 15) had a significantly lower number of larvae, infestation, deadheart and gave hig...

A survey was conducted to gain insight into the perceptions of Lesotho's farmers with regard to insect pests of maize and sorghum, to identify management practices that could impact on stalk-borer numbers and to shed light on other farming practices such as variety selection and crop residue management. Field studies were conducted to determine the incidence and distribution of Busseola fusca (Lepidoptera: Noctuidae) and Chilo partellus (Lepidoptera: Pyralidae) larvae in sorghum and maize residues and to determine the effect of certain crop residue management practices on stalk-borer survival. Results indicated that farmers regard stalk-borers as important pests that sometimes need to be controlled. However, most farmers never apply control measures, mainly due to lack of resources. Residues of maize and sorghum plants are largely used as animal fodder with maize being cut and fed to animals after harvest. Sorghum crop residues are largely left on fields after harvest to be used by free-grazing animals. W...

Cob rots are a major cause of crop loss in areas such as western Kenya that experience-prolonged rainfall during the period of crop maturation. Cob rot fungi cause spoilage of the grain and some of them produce mycotoxins which can pose a health risk to humans and animals consuming foods prepared from contaminated grain. Surveys conducted in western Kenya in 1998 showed that cob rot incidence exceeded 20%. In the following year when rainfall was greater around the harvest period, cob rot fungi a!ected 68% of cobs. In 1998 stalk borer larvae (mainly Busseola fusca) damaged 12% of cobs and there was a strong correlation (R"0.87) between cob rot incidence and borer damage. In 1999 almost half of the cobs sampled showed evidence of borer damage. The results indicate that the high cob rot incidence in this part of western Kenya is due to stalk borer damage, which predisposes the cobs to fungal infection, and that management of the borer would greatly decrease cob rot incidence. ( 2000 Elsevier Science Ltd. All rights reserved.