Pellagra

When maize was first introduced into other farming systems than those used by traditional native-American peoples, it was generally welcomed with enthusiasm for its productivity. However, a widespread problem of malnutrition soon arose wherever maize was introduced as a staple. This was a mystery since these types of malnutrition were not normally seen among the indigenous Americans, to whom maize was the principal staple food.

It was eventually discovered that the indigenous Americans learned long ago to soak maize in alkali-water—made with ashes by North Americans and lime (calcium oxide) by Mesoamericans—which liberates the B-vitamin niacin, the lack of which was the underlying cause of the condition known as pellagra. This alkali process is known by its Nahuatl (Aztec)-derived name: nixtamalization.

Besides the lack of niacin, pellagra was also characterized by protein deficiency, a result of the inherent lack of two key amino acids in pre-modern maize, lysine and tryptophan. Nixtamalisation was also found to increase the availability of lysine and tryptophan to some extent, but more importantly, the indigenous Americans had learned long ago to balance their consumption of maize with beans and other protein sources such as amaranth and chia, as well as meat and fish, in order to acquire the complete range of amino acids for normal protein synthesis.

Since maize had been introduced into the diet of non-indigenous Americans without the necessary cultural knowledge acquired over thousands of years in the Americas, the reliance on maize in other cultures was often tragic. In the late 19th century pellagra reached epidemic proportions in parts of the deep southern U.S., as medical researchers debated two theories for its origin: the deficiency theory (eventually shown to be true) posited that pellagra was due to a deficiency of some nutrient, and the germ theory posited that pellagra was caused by a germ transmitted by stable flies. In 1914 the U.S. government officially endorsed the germ theory of pellagra, but rescinded this endorsement several years later as evidence grew against it. By the mid-1920s the deficiency theory of pellagra was becoming scientific consensus, and the theory was proved in 1932 when niacin deficiency was determined to be the cause of the illness.

Once alkali processing and dietary variety was understood and applied, pellagra disappeared. The development of high lysine maize and the promotion of a more balanced diet has also contributed to its demise.

Pests

Insect pests

· Corn earworm (Helicoverpa zea)

· Fall armyworm (Spodoptera frugiperda)

· Common armyworm (Pseudaletia unipuncta)

· Stalk borer (Papaipema nebris)

· Corn leaf aphid (Rhopalosiphum maidis)

· European corn borer (Ostrinia nubilalis) (ECB)

· Corn silkfly (Euxesta stigmatis)

· Lesser cornstalk borer (Elasmopalpus lignosellus)

· Corn delphacid (Peregrinus maidis)

· Western corn rootworm (Diabrotica virgifera virgifera LeConte)

· Southwestern corn borer (Diatraea grandiosella)

The susceptibility of maize to the European corn borer, and the resulting large crop losses, led to the development of transgenic expressing the Bacillus thuringiensis toxin. "Bt maize " is widely grown in the United States and has been approved for release in Europe.