The environmental impacts of genetically modified (GM) crop plants such as Bt (Bacillus thuringiensis) maize have not yet been fully assessed in South Africa. Bt maize designed to express Bt endotoxin for control of Busseola fusca (Fuller) (Lepidoptera: Noctuidae) and Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) is planted on approximately 1.103 million hectares in South Africa. The monitoring of GM crops after release is important in order to assess and evaluate possible environmental effects. No risk assessment for Bt maize was done in South Africa before its release in 1998 and no targeted post-release monitoring of possible resistance development or impact on non-target species have been done. Awareness has risen in South Africa through research highlighting the possible effects GM crops may have. The aim of this study was to determine, through feeding experiments, the effects of Bt maize on selected non-target Lepidoptera, Coleoptera and Diptera species that occur in maize agro-ecosystems in South Africa. Results provide information for use in future risk assessment studies on Bt maize and indicate which species could possibly be of importance in post-release monitoring of Bt maize. Priority insect species were identified and laboratory- and semifield experiments were conducted to evaluate the effect of Bt maize on these species. In the light of the reportedly lower toxicity of Bt maize to certain noctuid borers, the effect of Bt maize was evaluated on Sesamia calamistis (Hampson), Agrotis segetum (Denis & Schiffermüller), and Helicoverpa armigera (Hubner). Feeding studies were also conducted to determine the effect of Bt maize on non-target Coleoptera, i.e. Heteronychus arator Fabricius (Coleoptera: Scarabaeidae) and Somaticus angulatus (Fahraeus) (Coleoptera: Tenebrionidae). The effect of indirect exposure of the stem borer parasitoid Sturmiopsis parasitica (Curran) (Diptera: Tachinidae) to Bt toxin was evaluated to determine if there is any effect when it parasitizes Bt-resistant B. fusca larvae that have fed on Bt maize. Results from the study conducted with S. calamistis indicated that Bt maize of both events (Bt11 and MON810) were highly toxic to S. calamistis. The behavioural characteristic of S. calamistis to feed behind leaf sheaths and to enter stems directly did not result in escape of exposure to the toxin. Larval feeding on leaf sheaths therefore resulted in the ingestion of sufficient toxin to kill larvae before they entered maize stems. Results showed that the effect of Cry1Ab toxin on the biology of A. segetum larvae and moths were largely insignificant. Whorl leaves were observed to be an unsuitable food source for H. armigera larvae and larval growth was poor. No larvae survived to the pupal stage on any of the Bt maize treatments. When feeding on maize ears H. armigera larval mass increased on non-Bt maize whereas no increase occurred on Bt maize. The feeding study conducted with Coleoptera showed that the effect of Bt maize on H. arator and S. angulatus was insignificant and no differences were observed in any of the parameters measured for the two species. Although not always significant, the percentage parasitism of Bt-consuming host larvae by S. parasitica was always higher compared to host larvae that fed on non-Bt maize. It could be that Bt toxin affects B. fusca fitness to such an extent that the immune systems of host larvae were less effective. The different parameters tested for S. parasitica indicated only one case where fly maggots originating from diapause host larvae feeding on non-Bt maize had a greater mass compared to host larvae that fed on Bt maize. The same applied to S. parasitica pupal length. For other parameters tested there were no significant differences. Sesamia calamistis is stenophagous and occurs in mixed populations with other borer species. It was therefore concluded that the ecological impact of local extinctions of S. calamistis caused by Bt maize is not expected to be great. Bt maize will most likely not have any significant effect on the control of A. segetum under field conditions. The feeding study conducted with H. armigera quantified the effects of Bt maize on this species and provided important information on the potential of Bt maize as protection against this polyphagous pest. However, the likelihood of H. armigera becoming an important secondary pest is high. It can be concluded that the Cry1Ab toxin targeting lepidopteran pests will not have adverse effects on H. arator or S. angulatus. Although some adverse effects were observed on S. parasitica mass and pupal length it is most likely that this will not contribute to adverse effects in the field, but that there rather be synergism between Bt maize and S. parasitica. An ecological approach was followed in which the potential effects of exposure of priority species to Bt toxin in maize was investigated. A series of selection matrixes were developed in which each of the above mentioned species was ranked for its maximum potential exposure to Bt toxin by assessing it occurrence, abundance, presence and linkage in the maize ecosystem. Through the use of these selection matrixes, knowledge gaps were identified for future research and to guide the design of ecologically realistic experiments. This study contributes to knowledge regarding the possible effects of Bt maize on the most economically important non-target pests in South Africa. There is, however, a need to evaluate other non-target species in feeding studies, as well as in field studies. From this study it can be concluded that some species can be eliminated from further testing since Bt maize had no adverse effect while more research have to be conducted on other species. / Thesis (Ph.D. (Environmental Science)--North-West University, Potchefstroom Campus, 2010.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

This study investigated the potential of companion planting as a strategy to aid in the management of Helicoverpa armigera in tomato and capsicum cropping systems. The investigaitons showed that a companion planting type system is unlikely to confer any benefits to the management of H. armigera in these crops. The project has contributed to the understanding of H. armigera host selection and how the pest responds to a diversified environment. Companion planting and vegetational diversity are strategies for reducing pest incidence on crops. Many theories have been devised to explain how introducing more than one plant species to a cropping space may reduce the incidence of a pest. Five ecological theories formed the basis of experiments in this study: The resource concentration hypothesis - Herbivores are more likely to find and remain on hosts that are growing in dense or nearly pure stands (Root, 1973). Associational resistance/Plant apparency - Crop plants grown as monocultures are more apparent to herbivorous insects than plants in diverse natural systems (Tahvanainen and Root, 1972). Trap cropping – the use of plants within a cropping area to attract oviposition away from the main crop (Banks and Ekbom, 1999). The ability of H. armigera to learn in regard to host seleciton (Cunningham et al., 1998a). The natural enemies hypothesis - generalist and specialist natural enemies are expected to be more abundant in diverse rather than simple systems (Root, 1973) A tall variety of sorghum (the forage variety Chopper) was tested for its ability to disrupt host location. Sorghum was planted around plots of tomatoes to act as a screen to disrupt visual cues for host location by Helicoverpa spp. No difference was found in egg numbers on tomatoes with or without sorghum companions. However, significantly higher numbers of Helicoverpa spp. larvae were found in the sorghum at flowering than in the tomatoes. This suggested the sorghum was acting as a trap crop, diverting oviposition away from the tomato crop. However, due to a short period of flowering and therefore peak attractiveness to H. armigera, sorghum was not considered to be a suitable companion plant for inclusion in commercial tomato production systems. A host preference study was conducted to determine the preferences of H. armigera for crop plants and possible companions in the hope of finding a suitable trap crop species. Tomatoes were shown to be a highly preferred plant making it difficult to find a compatible trap crop species that would be more attractive than the main crop. However, capsicums were less prefered and therefore more suitable for this type of experimentation. Marigolds were also found to be a highly preferred plant and formed the basis for further investigations into trap cropping systems. Field experiments were conducted in successive years in two geographical locations to assess the suitability of marigolds as a trap crop for capsicums in a field situation. However, in both years H. armigera incidence was extremely and unusually low leading to inconclusive results. A glasshouse experiment was performed to assess if the ratio of capsicum plants to marigolds plants had an effect on which species H. armigera would choose for oviposition. It was found that as more capsicum plants were introduced, moths became less likely to oviposit on the supposedly more preferred marigold plant. The diminishing attractiveness of a more preferred host in the presence of other hosts is a new observation of H. armigera behaviour. This result suggests that marigolds would be unlikely to be a successful trap crop in a field situation. The ability of H. armigera to learn in regard to host selection and the influence of this on host selection in the field was investigated. No evidence of learning was found. This was the first study investigating the effect of learning in a field situation; previously the behaviour had only been investigated in a laboratory situation (Cunningham, et al. 1998a). The ability of the Australian assassin bug, Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) to predate H. armigera larvae on capsicum plants was investigated. This predator has been sucessfully been used for H. armigera management in cotton (Grundy, 2000b), but had not been investigated in horticultural crops. Significant reductions in larvae were achieved in treatments where assassin bugs were introduced. This predator warrants further investigation for inclusion in commercial integrated pest managment programs for capsicums. Pest repellent plants were also considered. Previous to this study, very little research work had been conducted on repellent plants for H. armigera. The herbs investigated were catnip (Nepta cataria), tansy (Tanacetum vulgare), basil (Ocium basilicum) and coriander (Coriander sativum). An olfactometer system was designed and built to test H. armigera moths’ responses to odours from the herbs. Glasshouse experiments were also conducted. No repellent activity was recorded with any of the herbs tested. The results of this study support the theory that Helicoverpa spp. employ a strategy of passive host selection as suggested by Firempong (1986). This means that all available plants in an area may be oviposited on with successful ovipostion and larval development leading to the future utilisation of a species as a host plant. The implication of this finding is that in-field trap cropping is unlikely to be a successful strategy for reducing H. armigera oviposition in tomato or capsicum production systems in Australia. In cotton crops in Australia, trap cropping is used as part of an area wide management strategy and aims to reduce the total Helicoverpa spp. population of a region. Such a strategy may also be successful in horticultural crops but only with the full participation of the growers of all crops that are attractive to H. armigera in a horticultural growing region. Due to the diverse nature of horticultural production this may be a difficult task.

Submitted by (edna.saturno@ufrpe.br) on 2016-12-01T15:40:21Z No. of bitstreams: 1 Hugo Jose Goncalves dos Santos Junior.pdf: 559829 bytes, checksum: ef023fd54c27d2757f1cfcc6eb367bf7 (MD5) / Made available in DSpace on 2016-12-01T15:40:21Z (GMT). No. of bitstreams: 1 Hugo Jose Goncalves dos Santos Junior.pdf: 559829 bytes, checksum: ef023fd54c27d2757f1cfcc6eb367bf7 (MD5) Previous issue date: 2009-01-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The combined use of the entomopathogenic Bacillus thuringiensis Berliner with other arthropod natural enemies is an approach to improve the management of insect pests. Among the natural enemies, the egg parasitoid Trichogramma (Westwood) is recognized by its efficacy against various pest species in different agroecosystems, and can be used combined with B. thuringiensis. However, although B. thuringiensis exhibit several advantages, studies are required to ascertain about its selectivity for beneficial insects. The selection of isolates of B. thuringiensis is a way to assess the virulence to target insect pests, and the discovery of new toxins with higher entomopathogenic activity. Populations of Trichogramma should also be selected to avoid failure of its use, since this parasitoid has large variation regarding host preference and environmental conditions. Thus, this study selected isolates of B. thuringiensis (Bt) and populations of Trichogramma spp. to control of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). The selection methodology identified the Bt isolates Bt 23 and Bt 26 as promissory to control of H.zea. Among populations of Trichogramma evaluated there was variability in relation to the parameters analyzed and the thermal conditions, and the population of T. atopovirilia (Tatp1) exhibited the best performance at 25°C, and the populations Tp13 and Tp16 of T. pretiosum in thethermal conditions of 18 and 30ºC respectively. Based on these results, the populations Tatp1 of T. atopovirilia and Tp13 and Tp16 of T. pretiosum have potential as biological control agent against H. zea as well as the isolates Bt 23 and Bt 26 of B. thuringiensis. / A utilização conjunta de Bacillus thuringiensis Berliner com outros inimigos naturais é uma forma de incrementar o manejo de insetos-praga. Entre estes agentes, Trichogramma (Westwood) é reconhecido pela sua viabilidade e eficiência e, pode ser utilizado conjuntamente com B. thuringiensis. Porém, apesar de B. thuringiensis apresentar inúmeras vantagens, são necessários estudos que possibilitem comprovar sua seletividade a insetos benéficos. A seleção de isolados de B. thuringiensis é uma forma de avaliar a virulência a insetos-praga, além de possibilitar a descoberta de novas toxinas com maior atividade entomopatogênica. Populações de Trichogramma também devem ser selecionadas para evitar o insucesso da sua utilização, pois estes parasitóides apresentam grande variação, seja no comportamento de procura, preferência hospedeira e até mesmo às condições ambientais. Este trabalho teve como objetivo selecionar isolados de B. thuringiensis (B.t) e populações de Trichogramma spp. visando o controle de Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae). Os resultados apresentaram variabilidade emrelação à virulência dos isolados de B.t a H. zea, sendo que alguns não apresentaram índices satisfatórios de virulência, porém afetaram o desenvolvimento de H. zea. Foram identificados isolados promissores no controle de H. zea, a exemplo do B.t 23 e B.t 26. Entre as populações deTrichogramma avaliadas verificou-se variabilidade em relação aos parâmetros analisados e as condições térmicas, sendo que a população de T. atopovirilia (Tatp1) foi a que apresentou melhor desempenho a 25ºC e, as populações Tp13 e Tp16 de T. pretiosum nas condições térmicas de 18 e 30ºC respectivamente. Em virtude dos resultados encontrados, as populações de T. atopovirilia (Tatp1) e de T. pretiosum (Tp13 e Tp16) apresentam potencial para serem utilizadas em programas de controle biológico de H. zea.

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