Manipulating field margins to increase predation intensity in fields of winter wheat (Triticum aestivum)

Abstract

The effectiveness of natural enemies to control pests can be enhanced through habitat manipulation. However, due to the differences in their ecology, generalist and specialist species may respond differently to the same manipulation. Moreover, interactions among natural enemies (i.e. cannibalism, intraguild predation, hyperparasitism) may complicate the assumption that a higher density of natural enemies would increase the level of biological control. We investigated the natural enemy guild composition and the predation rate along flower vs. grass margins at the edge of winter wheat (Triticum aestivum) fields in Denmark. Natural enemies were sampled by pitfall trapping and by suction sampling; predation intensity was measured using two different sentinel prey methods: artificial caterpillars made of plasticine, and sentinel aphid colonies. Specialist and generalist species responded differently to the two margin types: specialists (mostly parasitic wasps) were attracted by the flower margins, while generalists (ground beetles, rove beetles and spiders) were more active in grass margins. The number of artificial caterpillars attacked was significantly greater in grass margins (mean = 48.9%, SD = 24.3) than in flower margins (mean = 30.7%, SD = 17.4). We found a significant positive relationship between the number of artificial caterpillars attacked by chewing insects, and activity density for large (≥15 mm) ground beetles. Predation of sentinel aphids in wheat fields did not vary significantly in relation to margin type. Our results suggest that flowering margins may be beneficial for canopy‐active specialist natural enemies, but grassy margins are more useful for ground‐active generalist predators.

The potential of trap and barrier cropping to decrease densities of the whitefly Bemisia tabaci MED on cotton in China

“…Cultural methods of control using varietal mixtures, intercropping or other cropping practices are not mainstream means of pest control and there is a need for additional research before they can be deployed effectively. Manipulating the habitat can enhance the biological control of crop pests in agroecosystems . Strip intercropping, growing two or more crops concurrently in different strips wide enough to permit independent cultivation but narrow enough for the crops to interact agronomically, can be adopted for various purposes, such as habitat diversification in agroecosystems for the benefit of insect predators, attracting pests away from the target crops and adding valuable biodiversity to agroecosystems.…”

Predators do not spill over from forest fragments to maize fields in a landscape mosaic in central Argentina

“…We found a positive correlation between total and chewing insect predation rates and live plant ground cover (H5 supported). Ground cover is important for soil surface‐active arthropods (Magura, ), which are probably a key group attacking artificial caterpillars (Ferrante et al., ; Mansion‐Vaquié et al., ), and which are abundant in chaco serrano (E. González, personal observation). Plant material affects soil pH, humidity, and organic content (Sadler, Small, Fiszpan, Telfer, & Niemela, ), and it is usually preferred by invertebrates to bare ground.…”

Agri‐environmental schemes affect the trophic niche size and diet of common carabid species in agricultural landscapes

“…Although organic farming still provides crop production in cereal fields, other types of AES apply to nonproductive areas (e.g. Mansion-Vaquié et al, 2017). These two AES types may differ in the provision of plant and animal food resources to invertebrate consumers, and thereby hold the potential to affect not only the number of generalist predators, but also their feeding ecology and resource utilisation.…”