Stefan TÖPFER, Lars REIMER & Ulrich KUHLMANN
CABI Bioscience Centre, Rue des Grillons 1, CH 2800 Delémont, Switzerland

Life table studies will be developed by CABI-CH to assess the significance of natural mortality factors acting on western corn rootworm (WCR) populations in its area of introduction in southeastern Europe (i.e. Hungary) within the EU Project DIABROTICA. Life tables will provide an understanding of the role of natural enemies, which function as mortality factors on certain life stages of WCR, and provide information on mortality factors that might potentially influence the population dynamics of the target pest. Furthermore the natural enemy guild concept will be used to characterize both structure and function of the natural enemy community present. Findings from this study will provide information about host niches of WCR that are presently not attacked by the natural enemy guild in southeastern Europe. This ecological information is required for further studies to identify and select potential biological control agents from the area of origin in central/South America.

In the 2000 season of the three-year EU project DIABROTICA, CABI-CH studied mortality factors attacking the larval, pupal and adult stages of WCR in Hungary. Studies were carried out with the intention to evaluate the impact of natural enemies (i.e. parasitoids and nematodes) on WCR life stages. In addition CABI-CH started studies to evaluate the temporal and spatial density within and between WCR life stages.  Finally, the realized fecundity of the beetle was studied in the field and in the laboratory. This information is needed for constructing complete life tables.

To obtain relevant life table parameters, a soil-root sampling program was carried out weekly in two maize fields to collect WCR larvae and pupae.  Samples were checked for larvae by eye and by using Berlese traps.  The mortality factors were recorded by rearing larvae to the adult stage and by dissecting larvae.  Adult beetles were collected on maize plants in fields in Hungary and Croatia and reared to assess potential mortality factors. In addition WCR adult density was calculated.

In conclusion no significant natural enemies have been found in Hungary in the year 2000.  Furthermore, mortality factors acting on third instar larvae and on young adults appear to be small.  In the following years, the soil-root sampling program will be intensified and the adult sampling will be increased to a wider range of countries.  Due to the lack of significant native natural enemies of WCR in southeastern Europe, a research program on exotic parasitoids will be conducted by CABI Bioscience Centre Switzerland.