While the discussion about GMO crops continues in India, in the US there’s a new factor in play: GMO weeds. Or, to be technically correct, weeds that develop resistance to Roundup. They’re Genetically Modified all right, but by Nature.

Monsanto has developed strains of “Roundup ready” (RR) seeds that are resistant to the weed-killer Roundup (also made by Monsanto). Farmers who plant RR crops can use large quantities of the herbicide, without killing their own crops.

This creates a strong evolutionary pressure on the weeds, so only those which can become resistant to Roundup survive.

One plant that’s met the challenge is a strain of  Amaranthus Palmeri, otherwise known as Pigweed. Ironically, this was a prehistoric crop species in the US (and related plants still are, including in India). But in modern over-fertilized farm conditions, it takes up too much nitrates, and its leaves become poisonous to livestock. It’s a very unpopular plant with US farmers.

As use of Roundup spreads, so does the Pigweed. It’s a pest in a number of crops, particularly cotton.

The kind of GMO crops being considered in India are not the “Roundup Ready” ones, which are resistant to herbicide, but rather the Bt crops that resist pests. Still, this is an object lesson in Unintended Consequences.