J. MOESER, S. VIDAL
Institute for Plant Pathology and Plant Protection, Georg-August-University Goettingen, Grisebachstr. 6, 37077 Goettingen, Germany; E-mail: jmoeser@gwdg.de

Since Diabrotica virgifera virgifera LeConte (Galerucinae, Crysomelidae) was introduced into Europe in the beginning of the 90’s this maize pest was continuously spreading and invading new areas and habitats in Central and Southeast Europe. Because the European agro-ecosystems presented a new ecological setting for this beetle, intensive studies were required on possible alterations in the ecology and behavior of the Western Corn Rootworm (WCR) adults. The study presented here gives information on the feeding behavior and use of weeds as alternative pollen resource on the basis of gut content analysis.

This study was performed in southern Hungary during a 10 week period collecting beetles in fields with different degrees of weed abundance to estimate the use of weed-pollen by WCR. Beetles were also collected directly from weeds when encountered there. The maize phenology was recorded once a week to gather information on availability of different maize tissues or organs. Furthermore the abundance and diversity of flowering weeds was recorded weekly along a transect inside the maize field. More than 600 beetles were used for a qualitative and quantitative pollen analysis were the insects were acetolysed and only the pollen remained. The pollen were counted and identified using a previously established reference collection of all weeds encountered inside and along the margins of maize fields.

It was possible to identify more than 10 weed species that were used by WCR as alternative pollen resources. from these Amaranthus sp. / Chenopodium album, Ambrosia artemisiifolia, Xanthium strumarium and Helianthus annuus were the most prominent. The differences concerning the use of weed pollen between adult WCR caught in fields with a high abundance of weeds and in field  with a low abundance of weeds were specific for the weed species. Differences were found between the two field categories regarding Amaranthus sp. / Chenopodium album but not regarding A. artemisiifolia. a tendency could be observed that WCR adults are mainly opportunistic pollen feeders but show a preference for some specific weed species.