If the grain carries the Bt gene, many ear-feeding insects should be controlled and the chance for mycotoxin infection would be reduced. But Vincelli says success also depends on the insect. “The effectiveness of the Bt trait in reducing mycotoxin contamination depends on the insect pest present. For example, Bt corn is often effective at reducing feeding damage from the European corn borer, but not the corn earworm. Consequently, reductions in fumonisin contamination may occur if the European corn borer is the principal pest in a field, but not if the corn earworm is predominant.
But Vincelli also says not all hybrids will have the Bt genetics in the ear. “The Bt trait is not a “silver bullet”, eliminating all mycotoxin risk. However, reductions occur commonly enough, with no known “downside”, that the Bt trait is thought to contribute to food safety and livestock health in both developed and developing countries. While it is well-documented that the Bt trait can reduce mycotoxin contamination, it is best used wisely, and only in fields with a moderate to high risk of damage from the target insect pests.”
Some Bt hybrids will be able to shield themselves against mycotoxins that are produced in the fungus in droughty corn. The fungus typically attacks on the corn ear where insects have physically damaged the kernels. The Bt hybrid that carries the Bt gene into the grain will help prevent a mycotoxin infection, since it may be able to control ear-feeding insects. But not all Bt hybrids have that capability.
Source: FarmGate blog