Inventarisation of natural enemies in witloof chicory fields: preliminary results.

Due to residues on the witloof chicory heads the use of insecticides is forbidden during forcing. At this moment a suitable chemical control of the leafminer Napomyza cichorii is carried out in the field, based on the phenology and the population density and taking into account the economic threshold level. No chemical treatment is recognized against the root aphid Pemphigus bursarius. For monitoring these pests during the growing season water traps were placed on observation fields, scattered over the Belgian endive production area. The large numbers and the wide variety of other insects caught in the traps in recent years indicate that there is a potential of natural enemies. An inventarisation of the native enemies in witloof chicory fields was started recently using yellow-coloured water traps and pitfall traps; at the same time field observations were done. In all the observation fields we found besides Carabidae and Staphilinidae also Coccinellidae and Syrphidae in large numbers. The numbers and the diversity of Hymenoptera in the water traps were very large. Apart from the field observations witloof chicory heads were investigated during harvest. Parasitized pupae were collected and kept in a climate room. Dacnusa leptogaster (Braconidae), a specific parasite of the witloof chicory fly, hatched. This parasite was also found in the water traps during the growing season.