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Response of Helicoverpa armigera to agricultural environments diversified through companion planting.Renee Herde Unknown Date (has links)
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.
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Response of Helicoverpa armigera to agricultural environments diversified through companion planting.Renee Herde Unknown Date (has links)
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.
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Response of Helicoverpa armigera to agricultural environments diversified through companion planting.Renee Herde Unknown Date (has links)
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.
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Response of Helicoverpa armigera to agricultural environments diversified through companion planting.Renee Herde Unknown Date (has links)
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.
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Host range of lichenivorous moths with special reference to nutritional quality and chemical defence in lichensPöykkö, H. (Heikki) 30 November 2005 (has links)
Abstract
Host use and range of herbivorous insects are determined by several factors, of which nutritional quality and secondary chemistry have been shown to play very important roles. For herbivores feeding on lichens these traits are assumed to be more critical than for species feeding on higher plants, since lichens are nutritionally poor and often contain high concentrations of secondary metabolites. I examined the role of lichens' nutritional quality and secondary chemicals on the performance of lichen-feeding Lepidopteran larvae. I also tested whether females of lichenivorous species preferably oviposit on host species of the highest nutritional quality for the growth of larvae.
Larvae of Eilema depressum performed best on Melanelia exasperata, which is of the highest nutritional quality, as indicated by the high N concentration and the absence of lichen secondary metabolites compared to the other lichens studied. Host nutritional quality did not promote the production of an additional generation. Larvae of E. depressum needed fewer instars and grew bigger on a high-quality diet than larvae reared on a diet of poorer quality. However, the main factor contributing to the wide variation in the number of larval instars was the question of whether or not larvae overwintered. Growth of Cleorodes lichenaria at the beginning of the larval period matched equally the nutritional quality of the hosts. However, the final larval period was shortest on Ramalina species, which was preferred by both females ovipositing their eggs and larvae searching for a host. In the field, larvae were found almost exclusively on Ramalina species.
Larvae of E. depressum were not able to survive on intact thalli of Vulpicida pinastri and Hypogymnia physodes, but after removal of lichen's secondary metabolites, larval survival remained equally high as on other lichens. Larvae also showed a clear preference towards thalli with lowered concentrations of secondary metabolites in Parmelia sulcata, V. pinastri and H. physodes. Parietin in Xanthoria parietina was the only secondary metabolite that had no impact on the survival or host selection of E. depressum larvae.
The present results show that the nutritional quality and some lichen secondary chemicals are important factors for the growth, survival and host selection of lichen-feeding Lepidopteran larvae. The preference-performance hypothesis is at least partly able to explain the host range of C. lichenaria, although it seems that there are also other factors, such as larval dispersal and host selection or top-down forces, that might contribute to host range of lichenivorous Lepidopteran larvae. Moreover, lichenivorous larvae seem to be partly responsible for their own host selection.
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Nutrição do tomateiro e sua influência no desenvolvimento de ninfas de Bemisia tabaci (GENN.) biótipo B / Tomato nutrition and its effect on the development of Bemisia tabaci (GEEN.) nymphs biotype BOliveira, Marcos Fernandes 17 February 2012 (has links)
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Previous issue date: 2012-02-17 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / The objective of this work was to evaluate the effect of tomato plants nutrition
on the development of B. tabaci (Genn) biotype B. The experiments were carried out in a
completely randomized design in a greenhouse at ambient temperature, moisture and
photoperiod, at the Escola de Agronomia e Engenharia de Alimentos (EA/UFG), Goiânia,
Goiás, Brasil. Each treatment had eight replicates with one plant per pot. Treatments used
to test the various contents of earthworm manure were the association of (soil + earthworm
manure: 100% + 0%; 80% + 20%; 60% + 40%; 40% + 60%; 20% + 80%, and 0% + 100%.
Treatments used to test the N/K rates were: 1/1; 2/1; 4/1; 8/1; 1/2; 1/4, and 1/8. To test the
different sources of organic nitrogen, the following treatments were used: chicken manure;
earthworm manure; cotton meal; castor beans meal, as well as the mixtures (chicken
manure + earthworm manure + cotton meal + castor beans meal. To test the various
sources of mineral nitrogen, the following treatments were used: urea, ammonium sulfate;
LL®; calcium nitrate and a mixture of fertilizers (urea + ammonium sulfate + Nitro LL® +
calcium nitrate). The infestations were performed 40 days after plugs transplant, by
releasing 50 couples of B. tabaci biotype B into screen bags, placed in the third or fourth
leaf of each plant. One day after infestation 300 eggs were counted and marked on each
infested leaf. Ten days after infestation the amount of unviable eggs were evaluated and
first ínstar nymphs marked. The analysis of nymphs development was performed 21 days
after infestation in the experiment used to test different sources of nitrogen and N/K rates;
and, at 30 days after infestation in the experiments used to test the different levels of
earthworm manure. B. tabaci nymphs biotype B showed elongation and mortality in that
phase, probably due to antibiosis developed by tomato plants: cultivated in earthworm
manure only (egg-adult viability 30% and 44% population reduction); fertilization
according to N/K 1/8 rate (egg-adult viability 13% and 69% population reduction);
fertilized with chicken manure (30% egg-adult viability and 41% population reduction);
and, fertilized with calcium nitrate (25% egg-adult viability and 57% population
reduction). / O objetivo dessa pesquisa foi avaliar a influência da nutrição do tomateiro no
desenvolvimento de ninfas de B. tabaci (Genn.) biótipo B. Os experimentos foram
conduzidos em delineamento inteiramente casualizado, em casa de vegetação e em
condições de temperatura, umidade e fotoperíodo naturais, na Escola de Agronomia e
Engenharia de Alimentos (EA/UFG), Goiânia, Goiás, Brasil. Cada tratamento foi
composto por oito repetições, com uma planta por vaso. Os tratamentos utilizados para
testar os diferentes teores de esterco de minhoca, na nutrição do tomateiro, foram às
associações solo + esterco de minhoca: 100% + 0%; 80% + 20%; 60% + 40%; 40% +
60%; 20% + 80%; 0% + 100%. Os tratamentos utilizados para testar as diferentes relações
N/K, na nutrição do tomateiro, foram às relações: 1/1; 2/1; 4/1; 8/1; 1/2; 1/4; 1/8. Para
testar as diferentes fontes de nitrogênio de origem orgânica, na nutrição do tomateiro,
foram utilizados os tratamentos: esterco de galinha; esterco de minhoca; torta de algodão;
torta de mamona e; mistura dos adubos (esterco de galinha + esterco de minhoca + torta de
algodão + torta de mamona). Para testar as diferentes fontes de nitrogênio de origem
mineral, na nutrição do tomateiro, foram utilizados os tratamentos: uréia; sulfato de
amônio; Nitro LL®; nitrato de cálcio e; mistura dos adubos (uréia + sulfato de amônio +
Nitro LL® + nitrato de cálcio). As infestações dos experimentos foram realizadas 40 dias
após o transplante das mudas, liberando-se 50 casais de B. tabaci biótipo B no interior de
sacos de tela antiafídeos, colocados na terceira ou quarta folha de cada planta. Um dia após
a infestação foi realizada a contagem e marcação de 300 ovos, em cada folha infestada.
Dez dias após a infestação foi avaliada a quantidade de ovos inviáveis e a marcação de
ninfas de primeiro ínstar. A análise do desenvolvimento das ninfas foi realizada aos 21 dias
após a infestação dos insetos, no caso dos experimentos utilizados para testar diferentes
fontes de nitrogênio e diferentes relações N/K e; aos 30 dias após a infestação dos insetos,
no caso dos experimentos utilizados para testar os diferentes teores de esterco de minhoca.
Ninfas de B. tabaci biótipo B apresentam alongamento e mortalidade dessa fase, com
provável ocorrência de antibiose, ao se desenvolverem em plantas de tomateiro: cultivadas
somente em esterco de minhoca (viabilidade ovo-adulto de 30% e redução populacional de
44%); adubadas segundo a relação N/K- 1/8 (viabilidade ovo-adulto de 13% e redução
populacional de 69%); adubadas com esterco de galinha (viabilidade ovo-adulto de 30% e
redução populacional de 41%) e; adubadas com nitrato de cálcio (viabilidade ovo-adulto de
25% e redução populacional de 57%).
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Life-history consequenses of host plant choice in the comma butterflySöderlind, Lina January 2012 (has links)
There is much evidence that herbivory is a key innovation for the tremendous success of insect. In this thesis I have investigated different aspects of host plant utilization and phenotypic plasticity using the polyphagous comma butterfly, Polygonia c-album. Even though external conditions affect a phenotypic plastic response, the outcome is often influenced by a genetic background which may differ among populations. In Paper I we suspected the genetic background to seasonal polymorphism to be X-linked. However, results from interspecific hybridization between two populations suggested that diapause response is instead inherited in a mainly autosomally additive fashion, with a possible influence of sexual antagonism on males. In Paper II we showed that female oviposition preference is not a plastic response influenced by larval experience, but has a genetic background coupled to host plant suitability. Further, there is a strong individual correlation between larval host plant acceptance and female host plant specificity (Paper III). We believe this to be a larval feed-back genetically linked to female host specificity: offspring to ‘choosy’ specialist mothers benefit by remaining on the original host while offspring to less discriminating generalist mothers should risk inspecting the surroundings, thus compensating for potential poor female choice. In the larval mid-gut, genes are differentially expressed depending on host plant diet (Paper IV). Therefore, we expected to find fitness consequences of host plant switch. However, although growth rate was affected in a few treatments, larvae were generally surprisingly good at adjusting to new diets (Paper V). To conclude, host plant choice in both female and larval life stage is connected to performance. Combined with increased understanding about the plastic response to diet intake and seasonal polymorphism we have gained further insights into the processes of local adaptations and speciation in the Lepidoptera. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted Manuscript; Paper 5: Manuscript
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Efeito da amplitude da dieta e da abundância de plantas sobre o uso de hospedeiras por insetos herbívoros em capítulos de asteraceae / Diet breadth mediates the host preferences of herbivorous insects in flower-heads of asteraceaeNobre, Paola Arielle Ferreira 19 March 2015 (has links)
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Previous issue date: 2015-03-19 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / the factors that influence the choice of egg-laying sites by adult insects is
critical in order to identify the major drivers of host-plant use by insects. The abundance
of different plant species and the level of feeding specialization of insects have been
considered as determinants of the preferential use of host-plants by herbivorous insects.
We analyzed the host use patterns of endophagous insects that feed on Asteraceae
flower-heads to test the following hypotheses: (i) the abundance of a plant species has a
positive effect on the preference of herbivorous insects for that plant species, and (ii) the
relative importance of plant abundance in determining preferential use is greater for
herbivorous species that use a wider range of host-plant species. We used data on the
interactions between herbivorous insects and Asteraceae host-plants family sampled in
20 Cerrado areas in São Paulo State. We analyzed 11 species of endophagous insects
and 12 host-plant species. For eight species of herbivorous insects, plant species
abundance showed a positive influence on herbivore preference. Three insect species
did not respond to any influence of plant abundance on feeding preferences, but one of
them showed a positive effect of plant species identity. Furthermore, both the most
specialized and the most generalist insect species presented a stronger positive effect of
plant species abundance in their choice of a host-plant. Therefore, our study shows that
the abundance of plant species is a major factor determining the preferential use of hostplants
by the endophagous insects of Asteraceae. Moreover, we show that herbivore diet
breadth mediates the relationship between host use and plant abundance. / Estudos abordando interações entre insetos herbívoros e plantas hospedeiras
abrangem uma vasta gama de aspectos ecológicos. Boa parte desses aspectos pode ser
relacionada diretamente ou indiretamente com a alta dependência que os herbívoros
apresentam em relação às suas plantas hospedeiras. Devido a essa alta dependência os insetos
herbívoros respondem tanto à riqueza e densidade, quanto ao arranjo espacial das hospedeiras
no habitat (Wright and Samways 1999, Summerville and Crist 2001, Tsharntke and Brandl
2004). Além das plantas hospedeiras proporcionarem recurso alimentar para os insetos, elas
também fornecem abrigo e microclima adequado para o desenvolvimento dos imaturos
(Gaston et al. 1992). Insetos herbívoros não consomem indiscriminadamente as plantas,
havendo geralmente alguma preferência por poucas espécies de plantas hospedeiras (Futuyma
and Gould 1979). Assim, mudanças, por exemplo, em aspectos quantitativo e qualitativo,
nessas hospedeiras podem ter grandes efeitos sobre as populações desses herbívoros. Nesse
contexto, pode-se dizer que a amplitude da dieta é um componente fundamental do nicho das
espécies de insetos herbívoros, influenciando desde sua dinâmica populacional e
suscetibilidade à extinção (Brown 1984), até sua distribuição geográfica (Strong et al. 1984).
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Structure génétique des populations du charançon de la carotte (Listronotus oregonensis) en Amérique du NordBessette, Marianne 05 1900 (has links)
Le charançon de la carotte (Listronotus oregonensis) s’avère un ravageur important des cultures d’apiacées en Amérique du Nord. Une recrudescence des dommages a été observée ces dernières années, et ce, malgré toutes les mesures de contrôle mises en place. Cette étude visait à déterminer la structure génétique des populations du charançon de la carotte en Amérique du Nord et d’évaluer le rôle de la distance géographique et de la plante hôte sur leur niveau de différenciation génétique. La préférence olfactive envers la plante hôte sur laquelle les charançons d’une même population s’y sont développés a aussi été analysée. La caractérisation de la structure génétique de L. oregonensis s’appuyait sur la discrimination des haplotypes (ADNmt COI) et des nucléotides (SNPs) par génotypage-par-séquençage (GBS). Dix-huit populations incluant 220 individus ont été échantillonnées au Québec, en Ontario, en Nouvelle-Écosse (Canada) et en Ohio (États-Unis). L’olfactométrie examinait la réponse olfactive de trois populations du Québec (195 femelles) en fonction de quatre plantes hôtes (carotte, céleri, céleri-rave et persil). Nos résultats ont montré que la distance géographique s’avère un facteur important de différenciation génétique entre les régions échantillonnées. Les analyses de GBS identifient la Nouvelle-Écosse comme étant la région la plus différenciée de toutes les populations analysées contrairement aux analyses de l’ADNmt COI qui suggèrent une différenciation récente. La plante hôte n’entraîne pas de signature génétique distincte chez le ravageur au Québec, et les trois populations testées n’ont pas présenté de préférence marquée pour une plante hôte, hormis la population issue du champ de carotte. Ces résultats suggèrent une capacité de dispersion limitée du charançon de la carotte à travers l’Amérique du Nord. / The carrot weevil (Listronotus oregonensis) is a major pest of apiaceae crops in North America. An upsurge in damage has been observed in recent years, despite all the control measures deployed. This study aimed to determine the genetic structure of carrot weevil populations in North America and to assess the role of geographic distance and host plants on their level of genetic differentiation. The olfactory preference of carrot weevils for the host plant on which the populations were collected was also analyzed. The characterization of the genetic structure of L. oregonensis was based on the discrimination of haplotypes (COI mtDNA) and nucleotides (SNPs) by genotyping-by-sequencing (GBS). Eighteen populations including 220 individuals were sampled in Quebec, Ontario, Nova Scotia (Canada) and Ohio (United States). Olfactometry examined the olfactory response of three populations in Quebec (195 females) according to four host plants (carrot, celery, celeriac and parsley). Our results showed that geographic distance was an important factor in genetic differentiation between the regions sampled. GBS analyzes identify Nova Scotia as the most differentiated region of all populations, unlike COI mtDNA analyzes, which suggest recent differentiation. The host plant did not demonstrate a distinct genetic signature in Quebec, and the three populations tested did not show a marked preference for a host plant, apart from the carrot field population. Finally, these results suggest limited dispersal of the carrot weevil across North America.
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Effets de la vibration (bruit blanc) sur la colonisation de Capsicum annuum et le succès reproducteur du puceron vert du pêcher Myzus persicaeDemers, Natali 04 1900 (has links)
cotutelle / La biotrémologie est l’étude de la vibration du substrat (ex. végétal) et de ses effets sur les animaux. En protection des cultures, la vibration du substrat s’utilise à la fois pour dépister les insectes ravageurs de culture et réduire leurs populations. Dans cette étude, nous avons évalué les effets de la vibration du substrat végétal sur l’acceptation de la plante hôte, la rétention, la fécondité et les comportements en période de mue du puceron vert du pêcher Myzus persicae, ravageur important des cultures notamment dans les serres de poivrons.
Des vibreurs ont été utilisés en laboratoire pour vibrer le substrat végétal en continu et à une même intensité de 24 h à 48 h. La vibration a réduit l’acceptation des plants vibrés par les pucerons ailés (-75%), comparativement aux plants témoins. Elle a également réduit la rétention des adultes, ailés et aptères (-33 à -46%, respectivement) et de leurs juvéniles (-50 à -65%, respectivement). Ces effets réducteurs ont augmenté avec la durée d’exposition vibrationnelle. Le traitement vibrationnel a eu également comme conséquence de réduire la fécondité des femelles aptères (réduction de 39% des juvéniles:adulte), après exposition au traitement. Les comportements de mobilité ont été plus longs avant la mue, alors que ceux d’alimentation ont été plus courts avant et après la mue chez les juvéniles soumis aux vibrations. La vibration induit un rejet de la plante hôte, réduit la fécondité et altère l’alimentation. La vibration du substrat se profile comme une méthode de lutte mécanique potentielle contre M. persicae. / Biotremology is the study of substrate-bone vibrations (e.g. via plants) and its effects on animals. In crop protection, substrate-borne vibrations are used both to detect crop pests and to reduce their populations. In this study, we evaluated the effects of plant substrate-borne vibrations on host plant acceptance, retention, fecundity and behaviour during the molting period of the green peach aphid Myzus persicae, a major crop pest particularly in bell peppers in greenhouses.
Shakers were used in the laboratory to vibrate the plant substrate continuously and at the same intensity from 24 h to 48 h. Vibrations reduced the acceptance of vibrated plants by alate aphids (-75%), compared with control plants. It also reduced the retention of adults, both alate and apterous (-33 to -46%, respectively) and their juveniles (-50 to -65%, respectively). These reducing effects increased with the duration of vibrational exposure. Vibrational treatment also resulted in reduced fecundity of apterous females (reduction of 39% of the juveniles: adult), after exposure to treatment. Mobility behaviours were longer before molting, while feeding behaviours were shorter before and after molting for vibration-treated juveniles. Substrate-borne vibrations induce rejection of the host plant, reduces fecundity and alters feeding. Substrate-borne vibration is emerging as a potential mechanical control method against M. persicae.
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