Are the Monarch butterfly caterpillars likely to encounter these harmful levels under natural conditions in the corn crop?
Researchers tried to answer these questions one at a time. They found that Monarch caterpillars are likely to be present in corn fields when corn plants shed their pollen, which means they are likely to eat some of the pollen. Once researchers found that Monarch caterpillars are likely to be exposed to corn pollen, they tested three different GM corn varieties containing different Bt toxins for harmful effects on Monarch caterpillars. They found that pollen from one of the three varieties contained 40-50 times as much Bt toxin as the two other varieties, and significantly harmed Monarch butterfly caterpillars. It caused slower growth at low pollen levels and death at high levels. In contrast, pollen from the two other varieties of GM corn tested had very low levels of Bt toxin and caused almost no harm to the caterpillars, even when eaten in large amounts. The same results were found in several different studies. These results showed that pollen from one GM corn variety in particular i
