Temporal and spatial overlap between monarch larvae and corn pollen
Authors: Oberhauser, K.S., Prysby, M.D., Mattila, H.R., Stanley-Horn, D.E., Sears, M.K., Dively, G., Olson, E., Pleasants, J.M., Lam, W.F., Hellmich, R.L.
Journal, Volume, Year: Proceedings of the National Academy of Sciences, volume 98:11913-11918, 2001
Milkweed and monarch densities in habitats available to monarch breeding were studied to determine the likelihood that monarch larvae will be exposed to Bt pollen. The authors concluded that a portion of monarch populations are exposed to and probably consume corn pollen that has collected on milkweed plants growing in cornfields. However, it is unlikely that the Bt corn hybrids most commonly planted produce sufficient levels of toxin in their pollen to cause adverse effects to monarchs. The authors also concluded that regardless of risks imposed by Bt corn, other agricultural practices (e.g., weed control and insecticide use) could have major impacts on monarchs.
Very good study assessing the possibility of hazards of Bt pollen to monarchs in the field.