| 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. |
- Björkman, Maria, et al.
(författare)
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Effects of plant competition and herbivore density on the development of the turnip root fly (Delia floralis) in an intercropping system
- 2009
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Ingår i: Arthropod-plant interactions. - : Springer Science and Business Media LLC. - 1872-8855 .- 1872-8847. ; 3, s. 55-62
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Tidskriftsartikel (refereegranskat)abstract
- In this study, interactive effects of plant competition and herbivory on plant quality and herbivore development were examined in a greenhouse experiment where cabbage plants [Brassica oleracea L. var. capitata (Brassicaceae)] were intercropped with red clover [Trifolium pratense L. (Fabaceae)]. Cabbages were grown with two red clover densities and attack rates by the root feeding herbivore the turnip root fly, Delia floralis Fall. (Diptera: Anthomyiidae). Above ground and below ground cabbage biomass was reduced through intercropping and larval damage. Intercropping also resulted in lower nitrogen and higher carbon root levels compared with levels in the roots of monocultured cabbage. Furthermore, both root nitrogen and carbon levels increased with herbivory. Root neutral detergent fibre (NDF) and lignin content increased in response to both increased plant competition and higher egg densities. For lignin, an interaction effect was observed in the form of elevated levels in intercropped plants subjected to larval damage, while levels in roots of monocultured cabbage remained unchanged. The quality changes brought about by clover competition affected D. floralis development negatively, which resulted in reduced pupal weight. In addition, increased egg density also decreased larval growth. The effects on the development of D. floralis in relation to host plant quality are discussed.
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| 3. |
- Björkman, Maria, et al.
(författare)
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Evaluating the enemies hypothesis in a clover-cabbage intercrop : effects of generalist and specialist natural enemies on the turnip root fly (Delia floralis)
- 2010
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Ingår i: Agricultural and Forest Entomology. - : Wiley. - 1461-9555 .- 1461-9563. ; 12:2, s. 123-132
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Tidskriftsartikel (refereegranskat)abstract
- The relative importance of the resource concentration hypothesis and the enemies hypothesis was investigated for the turnip root fly Delia floralis in a cabbage-red clover intercropping system compared with a cabbage monoculture. Delia floralis egg densities were measured as well as the activity-densities of generalist predators in a field experiment during two growing seasons. In the second year, a study of egg predation with artificially placed eggs was conducted, in addition to a predator exclusion experiment, to estimate total predation during the season. Parasitization rates were estimated from samples of pupae. Delia floralis oviposition was greater in the monoculture during both years. The predator activity-densities differed between treatments and study years. The known natural enemies of Delia spp., Bembidion spp. and Aleochara bipustulata showed a strong response to a cultivation system with higher activity-densities in the monoculture. The response, however, appeared to be caused primarily by habitat preferences and not by D. floralis egg densities. The reduction in the number of D. floralis pupae in the intercropping may be explained by a disruption in oviposition behaviour caused by the presence of clover because neither predation, nor parasitization rates differed between cultivation systems.
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| 4. |
- Björkman, Maria, et al.
(författare)
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Neighboring monocultures enhance the effect of intercropping in turnip root flies (Delia floralis).
- 2007
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Ingår i: Entomologia Experimentalis et Applicata. - : Wiley. - 0013-8703 .- 1570-7458. ; 124, s. 319-326
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Tidskriftsartikel (refereegranskat)abstract
- Knowledge of insect behaviour is essential for accurately interpreting studies of diversification and to develop diversified agroecosystems that have a reliable pest-suppressive effect. In this study, we investigated the egg-laying behaviour of the turnip root fly, Delia floralis (Fall.) (Diptera: Anthomyiidae), in an intercrop-monoculture system. We examined both the main effect of intercropping and the effect on oviposition in the border zone between a cabbage monoculture [Brassica oleracea L. var. capitata (Brassicaceae)] and a cabbage-red clover intercropping system [Trifolium pratense L. (Fabaceae)]. To investigate the border-effect, oviposition was measured along a transect from the border between the treatments to the centre of experimental plots. Intercropping reduced the total egg-laying of D. floralis with 42% in 2003 and 55% in 2004. In 2004, it was also found that the spatial distribution of eggs within the experimental plots was affected by distance from the adjoining treatment. The difference in egg-laying between monoculture and intercropping was most pronounced close to the border, where egg-laying was 68% lower on intercropped plants. This difference in egg numbers decreased gradually up to a distance of 3.5 m from the border, where intercropped plants had 43% fewer eggs than the corresponding monocultured plants. The reason behind this oviposition pattern is most likely that flies in intercropped plots have a higher probability of entering the monoculture if they are close to the border than if they are in the centre of a plot. When entering the monoculture, flies can pursue their egg-laying behaviour without being disrupted by the clover. As the final decision to land is visually stimulated, flies could also be attracted to fly from the intercropped plots into the monoculture, where host plants are more visually apparent. Visual cues could also hinder flies in a monoculture from entering an intercropped plot. Other possible patterns of insect attack due to differences in insect behaviour are discussed, as well as the practical application of the results of this study.
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| 5. |
- Cotes Ramal, Belén, et al.
(författare)
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A first approach to pest management strategies using trap crops in organic carrot fields
- 2018
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Ingår i: Crop Protection. - : Elsevier BV. - 0261-2194 .- 1873-6904. ; 112, s. 141-148
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Tidskriftsartikel (refereegranskat)abstract
- Cultural control methods in integrated pest management (IPM) refer to practices that modify the agricultural environment in ways that favour crop protection to the detriment of pest performance. Trap cropping is one of these practices and involves luring insect pests away from the main crop to a more attractive host plant growing beside or around the crop. The trap crop can then be destroyed, and the pest killed. The carrot psyllid, Trioza apicalis Forster (Homoptera: Triozidae), is one of the most important carrot pests in Scandinavia, and cultural control of this pest could be achieved through the introduction of more attractive cultivars of carrots in the trap crop at different sowing times than used for the main crop. In a multichoice bioassay and a field experiment, T. apicalis females oviposited the highest numbers of eggs on the most developed carrot plants in the trap crop, while different carrot cultivars did not play any role in females' choice, In the field experiment, probability of damage was highly correlated with number of eggs counted on the plants, which was highest on the most developed plants. The cultivar Bolero was used as trap crop in subsequent trials in three commercial carrot fields in different regions of Sweden. The trap crop concentrated the egg laying to the field edges and it decreased with increasing distance within the main crop from the first row of carrots, while this pattern could not be observed in control plots. These first results are promising, but further trials to better quantify efficacy and to evaluate the spatial design of the trap crop in field, at different sites and population pressure, are needed before trap cropping can be a reliable strategy for carrot psyllid control.
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| 6. |
- 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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| 7. |
- 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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| 8. |
- Delshammar, Tim, et al.
(författare)
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Stadsodling – reflektioner och perspektiv från SLU Alnarp
- 2012
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det är uppenbart att det mediala intresset för stadsodling har vuxit påtagligt de senaste åren. En sökning i databasen Retriever visar en ökande användning av begreppet ”urban odling” och en starkt ökande användning av ordet “stadsodling”. Olika medier påverkar så klart varandra. Radioprogrammet Odla med stadsgrönt började sändas våren 2009. Medier påverkar politiken som i sin tur påverkar medier. Den förste oktober 2009 lämnades motionen ”Stadsodling viktig i hållbara städer” in till riksdagen. Såväl media som politik påverkar och påverkas av praktiken. Våren 2009 började projektet Barn i stan odla i stadsdelen Seved i Malmö, ett projekt som uppmärksammats flitigt i media. Samma år började organisationen Stadsjord odla i stadsdelen Högsbo i Göteborg, även det flitigt uppmärksammat i media. Den statliga Delegationen för hållbara städer har beviljat bidrag till åtminstone fyra planeringsprojekt med inriktning mot stadsodling: SLU (sökt 2009), Plantagon (två projekt sökta 2010) samt Falun kommun (sökt 2012). Även investeringsprojekt har haft inslag av stadsodling, till exempel Malmö stads ansökan “Hållbar stadsomvandling Malmö, Fokus Rosengård” ( sökt 2010). Stadsodling finns med som ett inslag i flera aktuella stadsförnyelse- och stadsbyggnadsprojekt. Det har fått fungera som en symbol för kombinationen av ekologisk och social hållbarhet. En viktig fråga att reflektera över är därför hur hållbar stadsodling är. Vad kan vi ha för nytta av stadsodling? Hur kan odling ta plats i städerna? Hur kan vi stadsodla på ett hållbart sätt?
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| 9. |
- Hambäck, Peter, et al.
(författare)
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Scale-dependent responses in cabbage herbivores affect attack rates in spatially heterogenous systems
- 2009
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Ingår i: Basic and Applied Ecology. - : Elsevier BV. - 1439-1791 .- 1618-0089. ; 10, s. 228-236
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Tidskriftsartikel (refereegranskat)abstract
- Herbivorous insects face a dilemma when selecting suitable hosts in a complex environment, and their sensory capability may often reduce the female capacity for proper selection. As a consequence, eggs are often deposited on inferior hosts, affecting both insect and host plant fitness. We examined the attack rates of three cabbage herbivores in monocultures and biculture plots of different Brassica oleracea genotypes, with different spatial heterogeneity. The main goals of the study were to improve our understanding of the spatial scales involved in herbivore search processes and to examine the possibility of using spatial heterogeneity for manipulating pest attack rates in cabbage cropping systems. The results showed that the host selection behaviour of the small white butterfly (Pieris rapae) was strongly dependent on spatial heterogeneity. The difference in egg density between plant genotypes was larger when contrasting plants were growing in close proximity than in monoculture. This suggests that P. rapae is able to differentiate among genotypes from a small distance, while selection is compromised at larger spatial scales. The two other herbivores in the study (Mamestra brassicae and Delia radicum) did not respond to heterogeneity at any spatial scale, but showed a constant preference hierarchy. This suggests that host selection in these species occurs after direct plant contact. The difference in species’ responses to spatial heterogeneity has consequences both for selection gradients in natural communities and for the potential to reduce pest attack in polyculture systems.
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| 10. |
- Lagerlöf, Jan, et al.
(författare)
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Interaction between a fungal plant disease, fungivorous nematodes and compost suppressiveness
- 2011
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Ingår i: Acta Agriculturae Scandinavica, Section B - Soil and Plant Science. - : Informa UK Limited. - 0906-4710 .- 1651-1913. ; 61, s. 372-377
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Tidskriftsartikel (refereegranskat)abstract
- We tested the hypothesis that the fungivorous nematodes Aphelenchoides spp. and Aphelenchus avenae can suppress damping-off caused by Rhizoctonia solani in cauliflower seedlings, and enhance the disease-suppressive effect of compost. In greenhouse experiments, we used two different composts mixed with peat (20% + 80%) and pure peat as growth substrates in growing pots. In each substrate, treatments were: (A) with R. solani and nematodes, (B) with R. solani, (C) with nematodes, (D) control without R. solani or nematodes. Treatment effects were measured as percentage of healthy seedlings 7, 10 and 14 days after start of the experiment. We conducted two different experiments with the treatments A-D; one with Aphelenchoides spp. and one with Aphelenchus avenae. Aphelenchoides spp. +R. solani (treatment A) had 85% healthy plants (= control without addition of fungi (D)) compared with 45% in R. solani without nematodes (B). Aphelenchus avenae suppressed damping-off significantly in all substrates, from almost 100% dead plants in peat with R. solani to 65% healthy plants in R. solani vertical bar A. avenae. One compost mixture had an intrinsic suppressive effect on damping-off, while plant health in the other compost mixture was not better than in 100% peat as growing substrate. There were no additive suppressive effects (enhancement) between nematode effects and the suppressive compost. The results demonstrate the ability of fungivorous nematodes to suppress plant diseases. The effects of fungivorous nematodes in combination with compost and other control measures on disease suppression need further attention. The usefulness of fungivorous nematodes in agriculture and horticulture is discussed.
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