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AIR1-CT92-0339 Workshops
Enhancement, Dispersal and Population Dynamics of Beneficial Insects in Integrated Agro- Ecosystems - Workshops |
The workshops.
In accordance with the planning the first workshop was held in Aarhus (Denmark) (21-23 October 1993), the second workshop was held in Wageningen, Netherlands (1-3 December 1994) and the third workshop in Bristol, United Kingdom (23-25 November 1995). Due to a broad interest in the subject, a rather strict selection had to be made among potential participants. Finally for each workshop about 30 experts in the field of interest were invited to present papers and posters and to participate in discussion sessions. Both papers about results and methodologies, and discussion papers have or will be published to reach a broader audience. Many of the participants had not met before and contacts appeared to be very beneficial. Due to changing subjects, but also due to people changing scientific fields, only a hard core of about 10 researchers participated in each workshop and took care for the coherence and avoidance of redundant discussions. Each workshop was perfectly organised by the regional coordinators and fulfilled the original aim to discuss the bottlenecks and standardisation in methodology for studying and modelling field populations of beneficial organisms. Separate discussion sessions formed a major part of each workshop to evaluate the state of the art in particular fields and to discuss methodology.
Results of Workshop activities.
Workshop 1 Density, spatial heterogeneity and dispersal (Denmark). Contributions and discussions were organised around three themes being:
Advances and drawbacks of different trapping methods were explicitly summarised and guidelines were formulated to make international studies more comparable and to choose the right methodology for the scientific questions. Spatial heterogeneity appeared to be mostly considered as a disturbing and complicating factor is research and it is recognised that in particular at a larger scale data are scarce and also hard to obtain. Sampling in a heterogeneous environment appeared to be another problem which has to be solved. By making all new and possibly old data spatially explicit, geographic information systems and ARIMA models may help to judge the importance of spatial heterogeneity. Very different approaches are available to study dispersal by walking or flight ranging from harmonic radar tracking of individual carabid beetles in a field to monitoring a broad range of organisms by a network of dispersal-interrupting traps at the landscape scale. Dispersal appears to be not only species-specific - grouping of organisms in terms of dispersal and other ecological categories may be helpful -but also within species much variability is present (between populations, seasonal variation, and even between physiologically different individuals). There is a lack of data to feed models for dispersal (diffusion, individual based models, and landscape permeability) which are currently being developed.
Workshop 2 Survival, reproduction and enhancement (The Netherlands). Contributions and discussions were organised around three themes being:
Survival and mortality are complementary parameters which are most crucial in population studies of beneficial. Data derived from laboratory experiments cannot be easily translated to field situations but may give cues for further study under field conditions. Survival under field condition appears to be driven by multiple factors which are extremely variable in time and space. Dominant factors related to agricultural practices can be quantified and may provide handles to improve survival conditions for beneficials. Reproduction is much better studied both in laboratory and field conditions. In particular the relation with food availability is well established, though the level of food sources for polyphygous predators is difficult to assess. Indicator parameters like weight, size and hunger levels are useful to quantify habitat quality. Methods to manipulate habitat quality in terms of food level are hardly available apart from avoidance of pesticides. Field margins, unpsprayed zones, strip management and covercrops seem are promising agricultural practices to improve breeding condition for many beneficials but quantitative data are scarce. The same practices seem to be profitable for promoting higher numbers of beneficials whether by improving survival conditions or reproduction. The contribution of field margin management to overall field management is very scale dependent since effects have not been established over more than 30 meters. In-field management like covercrops etc. might be more effective in that respect.
Workshop 3 Analysis of population processes and modelling of dynamics (UK). Contributions and discussions were organised around three themes being:
Effects of the most important abiotic factors (temperature, humidity), biotic factors (like food availability) and human induced factors (pesticides and soil management) on behavior, in particular movement, and physiology (growth, starvation and reproduction) appear to be very complex. Individual data fed into population models mainly help to guide research and to provide frameworks. Their predictive power however appear to be very short term and small scaled. At the population level predictive models have been developed which are mainly based on plant-pest interactions and growth reducing factors like predation. Their practical application is mainly in within season prediction and supporting rules for supervised control including a judgement of the impact of beneficials. Assessment of ratio between pests and beneficials is more and more used. Spatial modeling is an increasing field of interest. Coupling GIS like systems with spatial population models is very much depending on source-sink data which are scarce and on information on dispersal and mortality rates (which are very difficult to measure). Community approaches to estimate impact of beneficials can be very useful when large research groups use the same theoretical framework and are able to quantify the impact of the major antagonistic groups. Very promising results are reached ', using supply/demand models as a background for tritrophic systems. The main question whether and why complexes of beneficials are better to regulate pest population can be linked to the impact of (functional) biodiversity in agro-ecosystems.
All papers presented at the workshops have been summarised. A compilation of summaries is available at the co-ordinators address. Presentations have been delivered by the participants as manuscripts for publication. After mutual reviewing system among participants, they were further processed by the workshop organisers for publication. Most of the presentations and results of discussion sessions are being published in special issues of Acta Jutlandica, from Aarhus University Press. At the time this report was made the issue is available as: Arthropod Natural Enemies in Arable Land: I Density, spatial heterogeneity and dispersal. Acta Jutlandica LXX: 2 Natural Science Series 9, 1-114. Aarhus University Press (ISBN 87 7288 492 4).
Contacts
Coordinator
EC Scientific Officer
Local Meeting Organiser
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Updated
by CPL Press:
03/07/2007
- biomatnet@biomatnet.org
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