Drift-reducing nozzles and their biological efficacy.

In 2007 and 2008, field trials were carried out with different standard and drift-reducing nozzles in sugar beet, maize, chicory, Belgian endive (all herbicide applications), wheat (fungicide application) and potatoes (Haulm killing herbicide application). The effect of nozzle type (standard flat fan, low-drift flat fan, air injection), nozzle size (ISO 02, 03 and 04) and application volume on the biological efficacy was investigated. All applications were done using a plot sprayer with volume rates ranging from 160 to 320 l.ha(-1) at recommended dose rates with commonly used (mix of) plant protection products. For each crop, the experiments included four replicates in a randomized block design. Depending on the type of application, the efficacy was measured in terms of weed control, disease and yield level, percentage dead leaf and stem, etc. In a previous research, drift and droplet characteristics of the different techniques were measured. In general no important effect of application technique on biological efficacy was observed for the tested herbicide and fungicide applications within the interval of volume rates and droplet size tested. Drift-reducing nozzles performed similar as conventional nozzles under good spraying conditions and using a correct spray application technique.

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.