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(246) Exposure of non-target-organisms on crop and off crop . Koch, Heribert1, Weisser, Peter1, 1 ABSTRACT- Spray deposits of plant protection products on cultivated plants present a potential hazard to non-ta get arthropods. This hazard is considered in the risk assessment procedure when such products are registered. The results of deposit measurements in the laboratory and field, including mean spray deposits on plant surfaces, their variability and their relation to the delivered dose are presented. Initial deposits expressed as ng/cm2 plant surface were measured on individual leaves of various plant species using a fluorescent tracer. The results show that the mean deposit is plant-specific but with a high degree of variability. Mean deposits on field-grown cereals were 0,19 (growth stage BBCH 10) and 0,23 - 0,7 ng/cm2 (growth stage BBCH 29 - 63) per g delivered per ha. On apple leaves, mean deposits varied between 0,9 and 2,5 ng/cm2 per g delivered per 10 000m2 fruitwall. Coefficients of variation of leaf deposits ranged between 30 % and 90 %. Other investigated plants were oats, onions and kohlrabi. In addition to the leaf-to-leaf variability, there was a notable variation of the deposit on individual leaves themselves as shown for wheat. Data from field measurements were supported principally by data from tray-grown plants on a laboratory spray track which gives information on targets positioned in a more or less two-dimensional system. There is need to reconsider the methodology of laboratory tests on beneficial organisms. In order to base risk assessment on more realistic parameters tests in the laboratora should be carried out with the dose that represents the exposure found in the field situation. The role of the variability of depsosits and thus exposure from leaf to leaf and on the leaf itself should be discussed. Recently started activities to develop an appropriate methodology for measurements of spray drift deposits in off-crop vegetation are also reported. It can be stated that the formation of "spray deposits" is very different compared to the processes that lead to a "drift deposit". Key words: exposure, risk assessment, ecotoxicology, pesticide registration |
