ABSTRACT: An important part of erosion control has been the implementation of low-till and no-till farming practices. These methods, however, have led to an increased reliance on herbicides to control weed populations. Glyphosate (a.k.a. RoundUp) is one of the most widely used herbicides, in part because of its low toxicity and its low persistence (rapid degradation) in the environment. Before RoundUp-resistant crops (or, RoundUp-Ready (RR) crops), it was standard practice to treat the entire field with herbicide to kill all weeds before planting. RR crops are designed to resist RoundUp so that herbicide can instead be applied to fields after crops have begun growing, only in those sections where weeds present a genuine problem, thus reducing the amount of herbicide required. The spread of RoundUp resistance beyond field boundaries, however, is a potential problem which needs to be addressed.

(Note: RoundUp-Ready crops (RR crops) are the only herbicide-resistant crop that I'm familiar with, so I will limit my discussion to this group of crops.)

Opponents to RR crops usually say that RR crops were designed so that farmers would have to spray more herbicides on their crops (and thus increase the profits of RoundUp manufacturers). But a quick look at the history of RoundUp and RR crops shows the opposite to be true:

It has long been recognized that preserving topsoil is one of the most important aspects of maintaining and sustaining fertile land. As a result, many farmers adopted low-till or no-till practices, in which plowing of the soil is kept to a minimum. This meant, however, that turning the soil over to bury and kill weeds before planting was no longer appropriate. So, many farmers turned to herbicides to kill the weeds before planting their crop. Basically, you would encourage the weeds to start growing in your field, then cover the entire plot in herbicide to kill them.

One of the most commonly used herbicides has been RoundUp, the brand name for the herbicide glyphosate. RoundUp became popular in large part because of its low toxicity toward mammals and because of its low persistence in the environment, meaning that it would break down quickly and reduce the risk of groundwater contamination.

When Monsanto's patent on glyphosate was set to expire (a few years ago), they developed RR crops in an attempt to preserve their share of the glyphosate market. These crops are resistant to RoundUp so that they may be used in the following way: Instead of growing up the weeds and then blanketing field in herbicide, you go ahead and plant the RR seeds; in the areas where weeds are a problem, you apply RoundUp to get rid of them, and in the areas where weeds are not a problem, you don't spray any herbicide. So instead of spraying the entire field, you spray only selected areas. Thus, RR crops are designed to reduce the amount of glyphosate used.

This raises the question, "Why would Monsanto develop a technology that reduces the need for herbicide?" The answer is that farmers who plant RR crops must agree to use only glyphosate purchased from Monsanto and not from a generic producer (since glyphosate is now off-patent). So even though the technology is supposed to decrease the amount of glyphosate purchased by the farmers, it is better for the company than losing the sales entirely.

The main concern with planting RR crops is the potential for RoundUp-resistant weeds. This can occur either through cross-pollination (if the crop is closely related to wild plants) or through accidental dispersal of seed.

Cross-pollination isn't a very likely problem except in the case of RR canola or rapeseed. These crops could potentially breed with wild Brassica species to produce weeds that are resistant to glyphosate. They would still be resistant to other herbicides or control methods (e.g., mechanical methods), but they could present problems if they become established in areas where RR crops are to be planted. RoundUp Read canola, then, is probably not a good idea.

Accidental dispersal of RR seed (e.g., by wind) is another problem that affects canola more than other crops. This is the type of situation that Terminator technology was meant to address, to prevent the unintended propagation of genetically engineered seed. Opponents have successfully blocked the adoption of this technology, so that the spread of, say, RR crops as weeds is now a potential problem.

On the whole, RoundUp-resistant crops seem to be a good idea, with the notable exception of RR canola. They can help reduce the amount of herbicide used to control weeds on the farm, but in certain cases the potential for spread of the resistance should be a matter of concern.

(October 2003)  

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