PARENT SESSION
TP4 Exposure assessment for aquatic and terrestrial risk assessment
3:00 PM to 6:30 PM, Tuesday, 08 May 2001
Session Chair: J. Gonzalez-Valero, J. Linders
Room 4

(248) Attempt to a risk assessment of spray drift in a field margin - a case study with grasshoppers.

Schenke, Detlef ¹, Kühne, Stefan¹, Kalthoff, Nina¹, Kaul, Peter¹, Gebauer, Sabine¹, ¹

ABSTRACT- Grasshoppers were caught in a 3-metre grass strip next to a wheat field treated with KARATE WG (7,5 g a.i./ha)2 and 3 days after treatment in 1998 and 1 day after treatment in 1999. The concentration of -cyhalothrin in grasshoppers determined after preparation and analysis using GC-MS²/NCI was a maximum of 4,4 x 10^-5 g a.i./g. When the values are referred to the area covered, it is possible to compare the measured exposure of the grasshoppers with the calculated basic drift values (Bundesanzeiger of 08.05.2000) used for estimation of exposure for authorisation purposes and with pesticide deposits in various heights in the field edge biotope. So the exposure of the grasshoppers to -cyhalothrin is by 10²-10³ less than the calculated basic drift values and the deposits measured with colour tracer (brilliant sulfoflavin) in these trials. We have no data on the toxic effect of -cyhalothrin on grasshoppers. But there are, however, laboratory LD₅₀ values for a number of organisms to which KARATE was topically applied in laboratory trials (Forster et al., Mitteilungen der Biologischen Bundesanstalt fuer Land- und Forstwirtschaft, Berlin-Dahlem 333). The maximum concentration measured in grasshoppers is still by 10² below the LD₅₀ of the most sensitive species studied. Knowing that the exposure of grasshoppers in field margins is very weak, and that only slight effect of spray drift on grasshopper populations has been estimated, a valid risk assessment still needs development of further basic toxicological data.

Key words: spray drift, field margin, grasshoppers, -cyhalothrin