Does all Bt corn pollen kill Monarch butterfly larvae?

Our answer to this question:

Yes

No

There are different varieties of Bt corn. Some varieties have pollen that contains high levels of the Bt toxin, enough to kill caterpillars that eat the pollen. Other varieties have pollen that contains low levels of the Bt toxin, not enough to kill caterpillars. The chart below shows several kinds of Bt corn along with the levels of Bt toxin in their pollen. You can see that Bt corn variety 176 has high levels of Bt toxin in the pollen grains. A plant of this variety will kill pests that attack the corn plant, such as the European corn borer, and will release pollen grain that might kill harmless insects, such as Monarch caterpillars eating milkweed plants in the corn field. Bt corn varieties 11 and MON810 have low levels of Bt toxin in the pollen. Plants of these varieties will kill pests that attack the corn plant, but will release pollen that does not harm insects on nearby plants.

Bt event promoter element(s)

amount of Bt protein in pollen

Bt 176 1) A promoter derived from a pollen-specific protein kinase in maize, linked to the Bt CryIA(b) gene. This promoter causes the Bt protein to be produced in the pollen.
2) A promoter derived from phosphoenolpyruvate carboxylase in maize, linked to the Bt CryIA(b) gene. This promoter causes the Bt protein to be produced in green tissues such as stems and leaves. There is little or no Bt protein produced in the kernels.
1.1 to 7.1 micrograms per gram of pollen
Bt 11 The promoter from the cauliflower mosaic virus 35S gene, linked to the Bt CryIA(b) gene. This promoter causes the Bt protein to be produced in all tissues of the plant. 0.09 micrograms per gram of pollen
MON810 The promoter from the cauliflower mosaic virus 35S gene, linked to the Bt CryIA(b) gene. This promoter causes the Bt protein to be produced in all tissues of the plant. 0.09 micrograms per gram of pollen