Author
Ursula Weigmann
Bio: Ursula Weigmann is an academic researcher from Canterbury of New Zealand. The author has contributed to research in topics: Melanostoma fasciatum & Biological pest control. The author has an hindex of 2, co-authored 2 publications receiving 224 citations.
Papers
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TL;DR: Border planting with P. tanacetifolia clearly affected numbers of adult hover flies and aphid populations, and the potential for this type of habitat manipulation to increase diversity as a component of integrated pest management is discussed with reference to comparable research in Europe.
Abstract: Brassicas in New Zealand are attacked by the cabbage aphid, Brevicoryne brassicae (L.); the green peach aphid, Myzus persicae (Sulzer); and the larvae of Artogeia rapae (L.) and the diamondback moth, Plutella xylostella (L.). Use of prophylactic pesticides is the usual control strategy against such pests, but the invertebrate predatory community within fields can contribute to pest suppression. Larvae of New Zealand hover flies consume all of the above pests, but the requirement of the adult flies for pollen and nectar may limit their potential in fields where the non crop flora is impoverished. In this work, parts of the borders of three cabbage fields were drilled with the annual plant P. tanacetifolia tanacetifolia Benth. (Hydrophyllaceae) as a pollen source in the spring. Four strips were alternated with 4 control strips (naturally occurring vegetation). Aphid and A. rapae populations were assessed weekly in unsprayed plots adjacent to the 8 replicated areas, and hover fly eggs were counted simultaneously. Hover fly adults were trapped in yellow pan traps that were arranged across the field in transects from each of the eight sampling areas. Border planting with P. tanacetifolia clearly affected numbers of adult hover flies and aphid populations. The potential for this type of habitat manipulation to increase diversity as a component of integrated pest management is discussed with reference to comparable research in Europe.
173 citations
TL;DR: There was good evidence of a second generation of hoverflies occurring in late summer and pollen preferences for both species of hoverfly were exhibited, and yellow was the most efficient color for trapping M. novaezlandiae but for M. fasciatum yellow, white, and blue did not differ and green was poor.
Abstract: Hoverflies are potentially important in many agricultural and horticultural crops as biological control agents. The two most abundant species of hoverflies present in the New Zealand agricultural landscape are Melanostoma fasciatum (Macquart) and Melangyna novaezelandiae (Macquart), both of which ar aphidophagous and also prey on young lepidopteran larvae. Information regarding the phenology and ecology of these species is quite limited but is needed if the contribution of these predators to biocontrol is to be enhanced. The main work reported here concerns the trapping of large numbers of hoverflies to investigate their phenology; these flies were subsequently assessed for the pollen type take and for wingwear. Foraging behavior, optimal trap color, and ideal trap-emptying rate were also studied. There was good evidence of a second generation of hoverflies occurring in late summer and pollen preferences for both species of hoverfly were exhibited. The foraging behavior of the two species differed in relation to the number of flights made and the overall distance traveled over fixed time intervals. Yellow was the most efficient color for trapping M. novaezlandiae but for M. fasciatum yellow, white, and blue did not differ and green was poor. The value of the work in providing backgroun ecological information for possible enhancement programs for hoverfly populations on farmland is discussed.
64 citations
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TL;DR: The rapidly expanding literature on habitat management is reviewed with attention to practices for favoring predators and parasitoids, implementation of habitat management, and the contributions of modeling and ecological theory to this developing area of conservation biological control.
Abstract: ▪ Abstract Many agroecosystems are unfavorable environments for natural enemies due to high levels of disturbance. Habitat management, a form of conservation biological control, is an ecologically based approach aimed at favoring natural enemies and enhancing biological control in agricultural systems. The goal of habitat management is to create a suitable ecological infrastructure within the agricultural landscape to provide resources such as food for adult natural enemies, alternative prey or hosts, and shelter from adverse conditions. These resources must be integrated into the landscape in a way that is spatially and temporally favorable to natural enemies and practical for producers to implement. The rapidly expanding literature on habitat management is reviewed with attention to practices for favoring predators and parasitoids, implementation of habitat management, and the contributions of modeling and ecological theory to this developing area of conservation biological control. The potential to int...
2,705 citations
TL;DR: It is concluded that diversified landscapes hold most potential for the conservation of biodiversity and sustaining the pest control function and similar contributions of these landscape factors suggest that all are equally important in enhancing natural enemy populations.
Abstract: Agricultural intensification has resulted in a simplification of agricultural landscapes by the expansion of agricultural land, enlargement of field size and removal of non-crop habitat. These changes are considered to be an important cause of the rapid decline in farmland biodiversity, with the remaining biodiversity concentrated in field edges and non-crop habitats. The simplification of landscape composition and the decline of biodiversity may affect the functioning of natural pest control because non-crop habitats provide requisites for a broad spectrum of natural enemies, and the exchange of natural enemies between crop and non-crop habitats is likely to be diminished in landscapes dominated by arable cropland. In this review, we test the hypothesis that natural pest control is enhanced in complex patchy landscapes with a high proportion of non-crop habitats as compared to simple large-scale landscapes with little associated non-crop habitat. In 74% and 45% of the studies reviewed, respectively, natural enemy populations were higher and pest pressure lower in complex landscapes versus simple landscapes. Landscape-driven pest suppression may result in lower crop injury, although this has rarely been documented. Enhanced natural enemy activity was associated with herbaceous habitats in 80% of the cases (e.g. fallows, field margins), and somewhat less often with wooded habitats (71%) and landscape patchiness (70%). The similar contributions of these landscape factors suggest that all are equally important in enhancing natural enemy populations. We conclude that diversified landscapes hold most potential for the conservation of biodiversity and sustaining the pest control function.
1,659 citations
TL;DR: The results of this meta-analysis support the view that basal resources mediate top-down impacts on herbivores, and provide encouragement that manipulations of habitat complexity can be made in agroecosystems that will enhance the effectiveness of the natural enemy complex for more effective pest suppression.
Abstract: The structural complexity of habitats has been espoused as an important factor influencing natural-enemy abundance and food-web dynamics in invertebrate-based communities, but a rigorous synthesis of published studies has not heretofore been conducted. We performed a meta-analytical synthesis of the density response of natural enemies (invertebrate predators and parasitoids) to experimental increases and decreases in the structural complexity of their habitats using data from 43 published studies, reporting 62 independent taxa. Studies varied in structural complexity at two spatial scales (habitat and within-plant architecture) and comprised a diverse array of natural-enemy taxa (natural-enemy assemblage at large, the entire spider assemblage, hunting spiders, web-building spiders, mites, hemipterans, coccinellid beetles, carabid beetles, ants, and parasitoids). For all taxa combined, increasing habitat structure resulted in a large and significant increase in natural enemy abundance. Similarly, decreasing habitat structure significantly diminished natural enemy abundance. Separate meta-analyses at two spatial scales (habitat and within-plant architecture) found that increasing habitat complexity resulted in significant increases in abundance. In particular, manipulating levels of detritus at the habitat spatial scale had the strongest effect on natural enemy abundance. In general, most guilds of natural enemies were significantly affected when the structural complexity of the habitat was altered. Seven of nine natural enemy guilds were more abundant under conditions of increased habitat complexity, with hunting spiders and web-building spiders showing the strongest response followed by hemipterans, mites, and parasitoids. Spiders in particular were negatively affected when habitat structure was simplified. The mechanisms underlying the accumulation of natural enemies in complex-structured habitats are poorly known. However, refuge from intraguild predation, more effective prey capture, and access to alternative resources (alternative prey, pollen, or nectar), are possible candidates. Our analysis was unable to confirm that predators aggregate in complex-structured habitats because prey (mostly herbivores) are more abundant there. The results of this meta-analysis support the view that basal resources mediate top-down impacts on herbivores, and provide encouragement that manipulations of habitat complexity can be made in agroecosystems that will enhance the effectiveness of the natural enemy complex for more effective pest suppression.
668 citations
TL;DR: It is concluded that addressing ‘stacked’ ecosystem services with multiple ecosystem service goals can decrease agriculture’s dependence on ‘substitution’ methods such as the current reliance on oil-based agro-chemical inputs.
405 citations
TL;DR: The main control strategies are reviewed in the light of an integrated pest management approach for cereal aphids, which are among the most important in Europe as direct feeders and virus vectors.
341 citations