Western corn rootworm: Experiments on the improvement of monitoring at low population densities

An efficient monitoring of the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte, 1868 (Chrysomelidae, Coleoptera) is the most important precondition for convenient measures of eradication or containment. This research project aimed to assess the monitoring methods, especially at low population densities as currently observed in Germany. For this purpose, large-scaled field trials were designed in Bavaria and Upper Austria. The studies focused on the catchability, costs and by-catches of the pheromone-trap PAL in comparison to other trap types. In another experiment, different allocations of PAL traps in the corn field were examined. Finally, traps and pheromones often remain unused at the end of a monitoring season. Therefore the catchability of stored PAL traps in the next monitoring period was investigated. PAL traps captured beetles constantly on a high level. In addition to its low costs and reduced by-catches, the trap type PAL is recommended for the monitoring of western corn rootworm in Germany. Changes in locations of PAL traps within the corn field did not result in a higher catchability. At present, traps are placed in the fifth to eighth corn row and the results confirm to maintain this practice. Comparing the catchability of stored PAL traps to the catchability of fresh traps, stored traps resulted in comparable catches than fresh ones. It is concluded that traps and pheromones, which were stored dark and deep-frozen, can be used in the next season