# Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

## Simulation of dispersal rates of WCR (Western Corn Rootworm) with and without containment measures

A simulation model for spreading scenarios of WCR (Western Corn Rootworm) has been developed using the GIS software ArcView/ArcInfo (ESRI). The calculation is based on grid processing of ARC-Macro-Language with a grid extent of 250X250m. The programme checked each grid for the kind of crop for further processing.

The following spreading parameters are considered:
- Spreading rates of populations per year,

- Influence of possible containment measures (i.e. phytosanitary measures),

- Concentration of maize (analysis of high-risk areas), and

- Topography (elevation of mountains).

The dispersal rate of WCR in Europe was analysed starting with the discovery of the economic WCR infestation in Serbia at the beginning of the 1990ies. Dispersal rates of the WCR differed from year to year. The spreading of the WCR ranged from 60 to 100km per year without containment measures and from 0 to 37km with (FAO programme TCP/RER/6712). The simulation model used as an average a maximum WCR population-spreading rate of 80km per year without containment measures and of 20km per year with. The maximum spreading rate is reached by WCR in the succeeding year only if continuous maize is available in the infested area.

The concentration of maize in crop rotation is the main factor in the simulation model. In case of low maize concentration, multiplication factor and spreading pressure are very low. In this case, the spreading rate was reduced by a correction factor K, which is defined as follows: In case of >= 50 % of maize in crop rotation K = 1 and concentration of maize in % 2 in case of < 50 % of maize in crop rotation: K = 100 The following formula was used in the simulation model to calculate the spreading rate of the WCR: AR = FD K; where AR = spreading rate of the WCR; FD = distance of flight with containment measures (20km/year) or without (80km/year) and K = correction factor (see above). Furthermore, the topography was analysed in the infested areas of Southeast Europe.

Analysis showed that the WCR is not able to fly over altitudes of 900m, which was considered in the simulation model. However, it cannot be fully excluded that in some cases single individuals are floated by wind flows over mountains of more than 900m. We assume that this has no influence on the ongoing of spreading of populations of WCR in general. The lowest mountain chain in Western Europe is up to 800m and has valleys (often with maize), which favour progressive dispersal. Only the Alps have tremendous influence on the ongoing of spread in West Europe and are a natural barrier.

Any appropriate information is utilised in the WCR spreading simulation model. This simulation model was used to simulate the spreading rate in France, Germany, Italy, Austria, and Belgium and for Switzerland over ten years. For the Netherlands, the precise growing data for maize and digital maps are not suited. Therefore, simulation of possible spreading scenarios for the Netherlands was not possible.

Four scenarios were chosen for each country:
- Introduction via the international airport with and

- Without containment measures and

- Progression of ''natural spread' via the next potentially infested country with the starting point at a location near the border with and

- Without containment measures.

The used locations for the simulation of spreading scenarios are in Tab. 2.1. Using ArcView/ArcInfo software, different spreading scenarios of WCR were simulated for France, Germany, Italy, Austria, Belgium and Switzerland on maps and these data were also the basis for the cost/benefit analyses. Damage due to WCR is expected in the 5th to 7th year. This conforms with findings from the USA and Hungary (C. R. Edwards and J. Kiss, personal communication). Results are presented on coloured maps, showing the spreading of WCR with and without containment measures. These maps may be requested from the author.

## Reported by

Research Dept.
Biologisceh Bundesanstalt fur Land- und Forstwirtschaft
14532 Kleinmachnow
Germany
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