Corn which has been engineered to make it resistant to insects also has lower levels of mycotoxins, which are potentially dangerous to humans and animals and are produced by the fungi that cause plant diseases.
Insects can exacerbate the problems.
When larvae chew on stalks and kernels, they create wounds where fungal spores can enter the plant. Once established, these fungi often produce mycotoxins. Some of these, such as fumonisin, can be fatal to horses and pigs, and are probable human carcinogens. Bt-corn has become very popular with American farmers. This makes the plant tissue toxic to the European corn borer, a significant pest that hides in the stalks of the plant, making it difficult to control with chemical sprays.