Nontarget Effects of Bt Corn Pollen on the Monarch Butterfly

EPA Grant Number: U915536
Title: Nontarget Effects of Bt Corn Pollen on the Monarch Butterfly
Investigators: Hansen, Laura C.
Institution: Iowa State University
EPA Project Officer: Smith, Bernice
Project Period: September 1, 1999 through May 1, 2001
Project Amount: $60,405
RFA: STAR Graduate Fellowships (1999) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecological Risk Assessment


The objectives of this research project are to: (1) determine the levels of transgenic pollen on Asclepias syriaca plants placed within and adjacent to plots of transgenic Bacillus thuringiensis (Bt) corn; (2) assess mortality of Danaus plexippus (Lepidoptera: Danaidae) larvae exposed to field-deposited pollen; (3) quantify the effects of exposure of D. plexippus larvae and adults to a range of transgenic pollen densities that would likely be encountered in the field; and (4) quantify the use of milkweeds by monarchs, and survival of monarchs on milkweeds adjacent to Bt and non-Bt corn fields.


Field deposition of pollen was assessed by placing potted milkweed plants within and around a corn field. Circles of leaf were removed from the milkweed plants, and the pollen grains on the circle of leaf were counted. To assess mortality of monarch larvae from field-deposited transgenic and nontransformed pollen, leaf disks (0.79 cm2) were removed from milkweed plants located within and at the edge of non-Bt and Bt corn plots. A first instar monarch larva was placed on each leaf disk for 48 hours. To assess the effect of pollen densities similar to those observed in the field, three densities (14, 135, and 1,300 pollen grains/cm2) of transgenic (MAX 454, 7333Bt) and nontransgenic (4494) pollen were placed on a disk of Asclepias curassavica. One 12- to 36-hour-old monarch larvae was placed on each leaf disk. Following the 48-hour exposure to pollen, each larva was fed clean A. curassavica leaves daily, until pupation. To assess the use of milkweeds in the field, six sites with a high concentration of milkweeds adjacent to corn fields will be chosen—three planted with non-Bt hybrids and three with Bt hybrids. Monarch larvae, using milkweeds located within 100-m transects at three locations adjacent to the field edge (0, 5, 10 m) and within the field, will be counted, and instar will be noted once a week to determine the use of these plants by monarch larvae.

Supplemental Keywords:

fellowship, Danaus plexippus, Bacillus thuringiensis, Bt corn, transgenic pollen, pollen deposition.