Larvae assessing risk

Effects assessment, by, as in the case of risk assessment for chemicals and pesticides, determining a set of marker organisms (including algae, zebrafish, insect larvae, benthic worm, water flea, etc.) that represent ecosystem components and food networks and are used to indicate acute and chronic effects. This step is also used to define the predicted no-effect concentrations (PNECs). 

In fliis paper, a weight-of-evidence approach is described for the risk of exposure of monarch larvae to Bt com pollen and the inq>act of such etqrasure on populations of the monarch butterfly in eastern Norfli America (2). Our conclusions are based on collaborative research by scientists in the United States and Canada (5-6). This approach to risk assessment has been performed for many non-target species in relation to pesticides (7-70), industrial by-products (77-75) and other potential toxicants found in the environment (7 ). The approach to fliis process is consistent, well documented and standardized. It requires consideration of both flie expression of a toxicant and the likelihood of... 

Exposure to Bt com pollen depends on 1) the phenological overlap between monarch populations and com anthesis, 2) the spatial overlap between milkweeds used by monarchs and cornfields, and 3) the pollen densities encountered on leaves of milkweed plants in and near cornfield. Pollen from com plants within a particular field is shed over a period of 7-15 days during the season, le larvae develop over a more prolonged period. Potential for exposure of susceptible stages of monarch larvae to com pollen depends on synchrony of their development with pollen shed of com plants. Locations in Iowa, Maryland, Minnesota/Wisconsin and Ontario were monitored for phenological development of monarch populations and anthesis (4). Overlap of the more susceptible stages of monarchs, primarily l" and 2" instars, with pollen shed was considered for purposes of risk assessment. 

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