According to the European Guideline (91/414/EEG) no unacceptable consequences on terrestrial non-target organisms in their totality may appear with the application of plant protection products (PPP). Thus possible hazards must be determined for non–target arthropods not only in the field, but also in the adjoining field margins. In the risk assessment of PPP towards non-target arthropods only beneficial organisms are tested and so far no herbivorous insect species (e.g. grasshoppers) are considered. However, the potential risk of herbivorous insects being exposed to pestidices is very high since additionally to direct contact, they are also consuming exposed plants. A former diploma thesis showed that some grasshopper species being red listed in Germany, which are potentially exposed to the spray drift of pesticides and grasshopper larvae were suspected to be sensitive to pesticides but only a few studies treating direct or indirect effects. Therefore the main objective of this study was to identify the potential hazard of pesticide drift on grasshoppers in field margins.

For the assessment of the sensitivity of grasshopper larvae ecotoxicological laboratory studies were conducted, on the one hand. Five insecticides were tested in commercially available formulations on the larvae of Chorthippus under use of different exposure scenarios. A direct application as well as contact above surfaces, oral admission and the combination of the last two, were tested. On the other hand a large scale field sampling was conducted to assess the grasshopper species and population density of imagines on field margins along different cultivated landscapes, as well as in meadows.

The grasshopper larvae showed considerable differences in the sensitivity between the single active substance groups and exposure scenario. The exposition about the surface contact would correspond to a “worst case” scenario. The combination of contact and oral exposure represents the real field conditions the closest. The application on food only, did not result in the expected high mortality values for the grasshopper larvae.
The indicated sensitivity of the grasshoppers towards insecticides showed in the laboratory was confirmed by the results of the field study. Here the width of the field margin showed a clear influence on the density of the grasshoppers, which correlates with the drift of PPPs. The results of the field margins along from orchard make clear the influence of the PPP spray drift on a width from up to 20 m.

Related publications:

Pierstorf, R., Brühl, C. (2009): Effekte von Pflanzenschutzmitteln auf Heuschrecken (Caelifera: Acrididae). Poster presentation at the 14th Annual Meeting of the SETAC GLB 2009, Freising / Weihenstephan, Germany (more info).

Pierstorf, R., Schmitz, J., Brühl, C. (2009): Effects of plant protection products on grasshoppers in the agricultural landscape, Poster Presentation, Young Environmental Scientist Meeting (YES-Meeting), Landau, Germany (more info).

Rebecca Bundschuh, Juliane Schmitz, Mirco Bundschuh, Carsten A. Brühl (2012) Does drift of insecticide adversely affect grasshoppers (Orthoptera: Saltatoria) in field margins? A case study combining laboratory acute toxicity testing with field monitoring data. Environmental Toxicology and Chemistry. Vol. 31 (8), 1874–1879, DOI: 10.1002/etc.1895.