Effects of air pollution on natural enemies of the leaf beetle Melasoma lapponica

Interactions of insect pests and their natural enemies increasingly are being considered from a metapopulation perspective, with focus on movements of individuals among habitat patches (e.g., individual crop fields). Biological control may be undercut in short-lived crops as natural enemies lag behind the pests in colonizing newly created habitat. This hypothesis was tested by assessing parasitism of cereal leaf beetle (Oulema melanopus) and alfalfa weevil (Hypera postica) larvae at varying distances along transects into newly planted fields of small grains and alfalfa in northern Utah. The rate of parasitism of cereal leaf beetles and alfalfa weevils by their host-specific parasitoids (Tetrastichus julis (Eulophidae) and Bathyplectes curculionis (Ichneumonidae), respectively) was determined for earliest maturing first generation host larvae. Rates of parasitism did not vary significantly with increasing distance into a newly planted field (up to 250–700 m in individual experiments) from the nearest source field from which pest and parasitoid adults may have immigrated. These results indicate strong, rapid dispersal of the parasitoids in pursuing their prey into new habitat. Thus, across the fragmented agricultural landscape of northern Utah, neither the cereal leaf beetle nor the alfalfa weevil initially gained substantial spatial refuge from parasitism by more strongly dispersing than their natural enemies into newly created habitat. Additional studies, including those of colonization of newly planted crops by generalist pests and natural enemies, are called for in assessing these results with a broader perspective.

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Between a rock and an egg‐crushing place: selection pressure from natural enemies and plant defences on eggs of the viburnum leaf beetle in its native range

Ecological Entomology ◽

10.1111/een.12936 ◽

2020 ◽

Author(s):

Gaylord A. Desurmont ◽

Elven Kerdellant ◽

Nicolas Lambin

Keyword(s):

Natural Enemies ◽

Selection Pressure ◽

Leaf Beetle ◽

Plant Defences ◽

Native Range

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Linear woody landscape elements may help to mitigate leaf surface loss caused by the cereal leaf beetle

Landscape Ecology ◽

10.1007/s10980-020-01097-3 ◽

2020 ◽

Vol 35 (10) ◽

pp. 2225-2238

Author(s):

Károly Lajos ◽

Orsolya Császár ◽

Miklós Sárospataki ◽

Ferenc Samu ◽

Ferenc Tóth

Keyword(s):

Biological Control ◽

Natural Enemies ◽

Natural Enemy ◽

Leaf Surface ◽

Leaf Beetle ◽

Agricultural Landscapes ◽

Natural Habitats ◽

Landscape Elements ◽

Surface Loss ◽

Cereal Leaf Beetle

Abstract Context Woody semi-natural habitats serve as permanent habitats and hibernation sites for natural enemies and, through spillover processes, they play an important role in the biological control of insect pests. However, this service is also dependent on the amount and configuration of the dominating woody habitat types: linear landscape elements (hedgerows, shelterbelts), and more evenly extended plantations. Relating natural enemy action to the landscape context can help to identify the effect of woody habitats on biological control effectiveness. Objectives In the Central European agricultural landscapes such as in the Hungarian lowlands, where our study took place, woody linear elements are characterised by high, while woody areal elements, mostly plantations, by low biological and structural diversity. In this study, we aimed to determine which composition and configuration of woody linear and areal habitats in the landscape may enhance the effect of natural enemy action on plant damage caused by the cereal leaf beetle (CLB, Oulema melanopus). Methods Herbivory suppression by natural enemies was assessed from the leaf damage difference between caged and open treatments. These exclusion experiments were carried out in 34 wheat fields on plants with controlled CLB infections. The results were related to landscape structure, quantified by different landscape metrics of both woody linear and areal habitats inside buffers between 150 and 500 m radii, surrounding the wheat fields. Results The exclusion of natural enemies increased the leaf surface loss caused by CLBs in all fields. Shelterbelts and hedgerows in 150–200 m vicinity of the wheat fields had a strong suppressing effect on CLB damage, while the presence of plantations at 250 m and further rather impeded natural enemy action. Conclusions Our results indicate that shelterbelts and hedgerows may provide a strong spillover of natural enemies, thus contribute to an enhanced biological control of CLBs.

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High effectiveness of tailored flower strips in reducing pests and crop plant damage

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.1369 ◽

2015 ◽

Vol 282 (1814) ◽

pp. 20151369 ◽

Cited By ~ 90

Author(s):

Matthias Tschumi ◽

Matthias Albrecht ◽

Martin H. Entling ◽

Katja Jacot

Keyword(s):

Winter Wheat ◽

Pest Control ◽

Natural Enemies ◽

Leaf Beetle ◽

Crop Damage ◽

Landscape Complexity ◽

High Effectiveness ◽

Plant Damage ◽

Crop Area ◽

Natural Pest Control

Providing key resources to animals may enhance both their biodiversity and the ecosystem services they provide. We examined the performance of annual flower strips targeted at the promotion of natural pest control in winter wheat. Flower strips were experimentally sown along 10 winter wheat fields across a gradient of landscape complexity (i.e. proportion non-crop area within 750 m around focal fields) and compared with 15 fields with wheat control strips. We found strong reductions in cereal leaf beetle (CLB) density (larvae: 40%; adults of the second generation: 53%) and plant damage caused by CLB (61%) in fields with flower strips compared with control fields. Natural enemies of CLB were strongly increased in flower strips and in part also in adjacent wheat fields. Flower strip effects on natural enemies, pests and crop damage were largely independent of landscape complexity (8–75% non-crop area). Our study demonstrates a high effectiveness of annual flower strips in promoting pest control, reducing CLB pest levels below the economic threshold. Hence, the studied flower strip offers a viable alternative to insecticides. This highlights the high potential of tailored agri-environment schemes to contribute to ecological intensification and may encourage more farmers to adopt such schemes.

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