FIGURE 2.2 Examples of pollen and gene dispersal as a function of distance from edge of crop. Dispersal distances are expected to depend on local conditions and relative sizes of donor and recipient groups of plants.

butterfly larvae. Laboratory studies showed that young monarch larvae were killed by ingesting high doses of Bt corn pollen that had been experimentally dusted onto milkweed leaves (Losey et al. 1999). Another study by Hansen and Obrycki (1999c) obtained similar results when monarch larvae were placed on milkweed leaves that had been collected at the edges of Bt and non-Bt corn fields in Iowa and brought into the laboratory. Although both studies should be viewed as preliminary and actual

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