| 1. |
- Anderson, Peter, et al.
(författare)
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Utilization of synergies between conservation and inoculation biological control through niche partitioning and selective biodiversity
- 2011
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Modern agricultural practices have led to destruction of semi-natural habitats, ecosystems and ecosystem services, and a decrease in the numbers of natural enemies. Conservation biological control (CBC) is the practice of enhancing natural enemy efficacy through modification of the environment or of existing pesticide practices. An additional way to enhance the control effect of pest insects is to combine the strategy of CBC with inoculation biological control (IBC). IBC is the intentional release of a living organism as a biological control agent with the expectation that it will multiply and control the pest for an extended period, but not permanently. Increased natural enemy diversity in biological control has positive effects when the feeding niches of the natural enemies complement each other. By combining biological control agents separated in niche partitioning in time and space, the effect can be greater than the single compartments. In a previous research project we developed a system where two key pests of cabbage and onion (Delia radicum and D. antiqua, respectively are controlled using 1) crop rotation to disrupt their lifecycles and 2) semi-permanent selective flower- and grass strips to enhance the parasitoid wasp Trybliographa rapae and soil inhabitant generalist predators. The specialist larval parasitoid T. rapae as well as the generalist predator/pupal staphylinid parasitoid Aleochara bipustulata attack both Delia pests and, therefore, are not disrupted by the crop rotation which provides a less disturbed system. In a continuation of this project we are studying the impact of complementary biological control strategies on pest control of Delia spp and interactions between the control agents. We will combine IBC, using entomopathogenic fungi, with CBC of T. rapae and A. bipustulata in a crop rotation system. It is a novel ecologically-based management system that relies on the niche complementarity of natural enemies in time and space. The impact of the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae on T. rapae and A. bipustulata regarding intraguild interactions, behaviour and fitness will be investigated. The study further combines knowledge of biological control with studies in chemical ecology, to evaluate the role of chemical signals in ecological and as well as behavioural mechanisms. Other host-parasitoid systems have showed that there is fitness costs involved in developing on infected hosts. This will be evaluated for T. rapae and A. bipustulata by measuring fecundity and offspring number, quality (survival, weight, etc.), development and viability in laboratory cage experiments at different host infection levels. The preliminary results of bioassays regarding choice/no-choice and fitness consequences in T.rapae associated with infected host larvae will be presented and discussed in the context of the agroecosystem
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| 2. |
- Cotes Ramal, Belén, et al.
(författare)
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A host-pathogen-parasitoid system in the biological control of the cabbage root fly, Delia radicum
- 2014
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Ingår i: IOBC-WPRS Bulletin. - 1027-3115. ; 107, s. 190-190
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This project will investigate the impact of complementary biological control strategies on pest control of Delia radicum (and D. antiqua) and interactions between the control agents. We will combine inoculation biological control, using the entomopathogenic fungi Beauveria bassiana and Metarhizium anisopliae, with conservation biological control of the specialist parasitoid Trybliographa rapae and the generalist predator/parasitoid Aleochara bipustulata in a crop rotation system. It is a novel ecologically-based management system that relies on the combined effects of biological control strategies, through niche complementarity of natural enemies in time and space. We will present the preliminary results on the effect of the fungi in the system. The dose-response of the fungi on the third instar larvae of D. radicum will be given together with the preliminary results of bioassays regarding choice/no-choice in T.rapae associated with infected host larvae. Also the role of chemical signals in behavioral mechanisms have been started to be elucidated through studies in a two-choice olfactometer. The first year's data on mortality of D.radicum larvae caused by either/or in combination: T.rapae and M.anisopliae from cage semi-field trials will be presented. The implication of the results will be discussed in the context of the agroecosystem
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| 3. |
- Cotes Ramal, Belén, et al.
(författare)
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Habitat selection of a parasitoid mediated by volatiles informing on host and intraguild predator densities
- 2015
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Ingår i: Oecologia. - : Springer Science and Business Media LLC. - 0029-8549 .- 1432-1939. ; 179, s. 151-162
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Tidskriftsartikel (refereegranskat)abstract
- To locate and evaluate host patches before oviposition, parasitoids of herbivorous insects utilize plant volatiles and host-derived cues, but also evaluate predator-derived infochemicals to reduce predation risks. When foraging in host habitats infested with entomopathogenic fungi that can infect both a parasitoid and its host, parasitoids may reduce the risk of intraguild predation (IGP) by avoiding such patches. In this study, we examined whether the presence of the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana in soil habitats of a root herbivore, Delia radicum, affects the behavior of Trybliographa rapae, a parasitoid of D. radicum. Olfactometer bioassays revealed that T. rapae avoided fungal infested host habitats and that this was dependent on fungal species and density. In particular, the parasitoid avoided habitats with high densities of the more virulent fungus, M. brunneum. In addition, host density was found to be important for the attraction of T. rapae. Volatiles collected from host habitats revealed different compound profiles depending on fungal presence and density, which could explain the behavior of T. rapae. We conclude that T. rapae females may use volatile compounds to locate high densities of prey, but also compounds related to fungal presence to reduce the risk of IGP towards themselves and their offspring.
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| 4. |
- Mendesil, Esayas, et al.
(författare)
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Oviposition Preference of Pea Weevil, Bruchus pisorum L. Among Host and Non-host Plants and its Implication for Pest Management
- 2016
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Ingår i: Frontiers in Plant Science. - : Frontiers Media SA. - 1664-462X. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The pea weevil, Bruchus pisorum L. is a major insect pest of field pea, Pisum sativum L. worldwide and current control practices mainly depend on the use of chemical insecticides that can cause adverse effects on environment and human health. Insecticides are also unaffordable by many small-scale farmers in developing countries, which highlights the need for investigating plant resistance traits and to develop alternative pest management strategies. The aim of this study was to determine oviposition preference of pea weevil among P sativum genotypes with different level of resistance (Adet, 32410-1 and 235899-1) and the non-host leguminous plants wild pea (Pisum fulvum Sibth. et Sm.) and grass pea (Lathyrus sativus L.), in no-choice and dual-choice tests. Pod thickness and micromorphological traits of the pods were also examined. In the no choice tests significantly more eggs were laid on the susceptible genotype Adet than on the other genotypes. Very few eggs were laid on P. fulvum and L. sativus. In the dual-choice experiments Adet was preferred by the females for oviposition. Furthermore, combinations of Adet with either 235899-1 or non-host plants significantly reduced the total number of eggs laid by the weevil in the dual choice tests. Female pea weevils were also found to discriminate between host and non-host plants during oviposition. The neoplasm (Np) formation on 235899-1 pods was negatively correlated with oviposition by pea weevil. Pod wall thickness and trichomes might have influenced oviposition preference of the weevils. These results on oviposition behavior of the weevils can be used in developing alternative pest management strategies such as trap cropping using highly attractive genotype and intercropping with the non-host plants.
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| 5. |
- Mendesil, Esayas, et al.
(författare)
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Smallholder farmers' knowledge, perceptions and management of pea weevil in north and north-western Ethiopia
- 2016
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Ingår i: Crop Protection. - : Elsevier BV. - 0261-2194 .- 1873-6904. ; 81, s. 30-37
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Tidskriftsartikel (refereegranskat)abstract
- Pea weevil (Bruchus pisorum L.) is one of the most serious insect pests of field pea (Pisum sativum L) in Ethiopia. A survey of 400 farmers was conducted in four main pea-growing districts in north and northwestern Ethiopia. The objectives were to assess farmers' knowledge and perceptions of pea weevil, to examine their current pest management practices and to identify challenges to pea weevil control, so that participatory integrated pest management for smallholder farmers in Ethiopia can be developed. The results revealed that most (71%) of the farmers surveyed had knowledge about pea weevil and were able to identify damaged seeds based on common visible symptoms of weevil infestation. However, most farmers did not know that pea weevil attacks plants in the field, but rather considered it a storage pest. The results also showed that farmers' cultural practices influence the incidence and spread of pea weevil and that most farmers did not check seed for pea weevil symptoms before planting. Only a minority of farmers (19%) harvested peas early and some harvested late, unintentionally promoting infestation and carryover of weevils. In addition, most farmers (74%) were not aware of the source and means of weevil spread on their farm and some did not clean up fallen and shattered peas during harvesting and threshing. The majority (63%) of the farmers surveyed relied on chemical insecticides, namely actellic dust and phostoxin, to treat harvested peas in storage. However, the results revealed a knowledge gap in that farmers were well aware of the problem of pea weevil, but lacked knowledge of cultural practices affecting pea weevil and of problems in the use of pesticides. This highlights the need for farmer training and for development of participatory integrated pest management methods for pea weevil. (C) 2015 Elsevier Ltd. All rights reserved.
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| 6. |
- Nilsson, Ulf, et al.
(författare)
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Comparison of nectar use and preference in the parasitoid Trybliographa rapae (Hymenoptera: Figitidae) and its host, the cabbage root fly, Delia radicum (Diptera: Anthomyiidae)
- 2011
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Ingår i: Biocontrol Science and Technology. - : Informa UK Limited. - 0958-3157 .- 1360-0478. ; 21, s. 1117-1132
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Tidskriftsartikel (refereegranskat)abstract
- This study investigated differences in flower preferences between the parasitoid Trybliographa rapae Westwood (Hymenoptera: Figitidae) and its host, the economically important pest of cruciferous crops, the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae). The data obtained were used to suggest selective food plants in conservation biological control programmes for control of D. radicum. The attraction of both insect species to floral odours emitted from nine different plant species, their ability to access nectar from four of these species and the effect of the most promising plant species on insect longevity were determined. Naive T. rapae females were significantly attracted to flower odours from Fagopyrum esculentum Moench. (Polygonaceae) and repelled by Coriandrum sativum L. (Apiaceae) and Borago officinalis L. (Boraginaceae). In addition, T. rapae gained weight when exposed to F. esculentum, Anethum graveolens L. (Apiaceae) and Lobularia maritima Desv. (Brassicaceae). In contrast, naive D. radicum females showed attraction to most of the flowers. The longevity of both T. rapae and D. radicum increased significantly when they were provided with flowering A. graveolens and F. esculentum. In addition to the laboratory studies, a semi-field experiment was made to study the impact of flowering F. esculentum on the ability of T. rapae to parasitise D. radicum larvae. Significantly more larvae were parasitised in cages where a floral resource was present. The findings are discussed in the context of a Brassica agroecosystem.
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| 7. |
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| 8. |
- Nilsson, Ulf, et al.
(författare)
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Effects of conservation strip and crop type on natural enemies of Delia radicum
- 2016
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 140, s. 287-298
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Tidskriftsartikel (refereegranskat)abstract
- This 3-year field study investigated the combined effect of floral resources and perennial shelter habitats (i.e. conservation strips), and crop rotation in supporting natural enemies of the cabbages root fly, Delia radicum. Habitat manipulation with conservation strips increased the overall catches of hymenopteran parasitoids. However, conservation strips did not increase parasitism by either of the two dominant parasitoid species, Trybliographa rapae and Aleochara bipustulata, in any study year. In fact, higher parasitism was found in control plots in the second year. This could be explained by parasitoid mobility and higher patch detectability, as more plants in the control plots were infested with D.radicum larvae. Conservation strips did not result in increased predation of D.radicum eggs. However, the activity densities of two Bembidion species were correlated with egg predation. The species assemblage distribution of epigeal predators was best explained by seasonal period, followed by year and, to a low extent, crop type, while treatment with conservation strips had no effect. However, during the egg laying peak of D.radicum, a higher number of A.bipustulata, an important larval predator was observed in conservation strips during one study year. In conclusion, positive effects of conservation strips were demonstrated for abundance of some natural enemies of D.radicum, but a consistent increase in performance could not be adequately demonstrated due to experimental set-up, the short timescale and the complex landscape in which our study site was located.
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| 9. |
- Nilsson, Ulf, et al.
(författare)
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Herbivore response to habitat manipulation with floral resources: a study of the cabbage root fly
- 2012
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Ingår i: Journal of Applied Entomology. - : Wiley. - 0931-2048 .- 1439-0418. ; 136, s. 481-489
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Tidskriftsartikel (refereegranskat)abstract
- Biological control of pest insects can be improved by providing natural enemies with additional food resources such as floral nectar within the production field. However, herbivores may also benefit from this practice. The aim of this 3-year field study was to investigate if dill and buckwheat, aimed as food resources for natural enemies, could increase the densities of the cabbage root fly, Delia radicum L. (Diptera: Anthomyiidae), a severe pest on crucifers. Differences in egg density, numbers of pupae and sex ratio were compared between cabbage plots with or without flowers. Habitat manipulation by intercropping flowering plants with cabbage did not increase the overall D.similar to radicum egg density in our 3-year study, and there were no significant differences in egg numbers between treatments in any year. No effect on the fecundity of D.similar to radicum was observed, most likely because of the high mobility and feeding behaviour of the female flies, combined with high abundance and diversity of other food sources around the fields during this period. Despite equal egg numbers, fewer pupae were found in plots with flowers than without in one of three studied years. This finding suggests that natural enemies attacking larvae and pupae of D.similar to radicum were either more abundant or efficient in cabbage plots with flowers.
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| 10. |
- Nilsson, Ulf, et al.
(författare)
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Male and female Trybliographa rapae (Hymenoptera: Figitidae) behavioural responses to food plant, infested host plant and combined volatiles
- 2012
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Ingår i: Arthropod-Plant Interactions. - : Springer Science and Business Media LLC. - 1872-8855 .- 1872-8847. ; 6, s. 251-258
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Tidskriftsartikel (refereegranskat)abstract
- Many parasitoids use volatiles produced by plants as important cues during their food and host search process. We investigated the attraction of the parasitic wasp Trybliographa rapae Westwood (Hymenoptera: Figitidae) to volatiles emitted from plants infested by the cabbage root fly Delia radicum L. (Diptera: Anthomyiidae), as well as to volatiles from a nectar food plant. Behavioural choice tests showed that male parasitoids were not attracted to any volatiles from plants infested by D. radicum or from nectar plants, while females showed clear attraction to both volatile sources. Young females were more attracted to combined volatiles of host and food plants over those from only the host plant, whereas older females showed no differences in attraction to the two odour sources. This suggests that intercropping attractive flowers with host plants could potentially be used to recruit newly emerged parasitoids from surrounding fields while older parasitoids invest more energy in host location than in additional food search. Volatiles from a whole infested plant were chosen over those emitted from separated above- and below-ground parts from infested plants. It is important to consider the availability of both energy and host resources for parasitoids when designing an eco-compatible management of a vegetable crop system.
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