Consumer Concern #4 - Environment
A study conducted at Cornell University raised concerns about the effects on Monarch butterfly larvae. Researchers reported that when butterfly larvae eat only pollen from Bt corn, many of them died or failed to thrive. In response to that laboratory study, more assessment was done.
This close look indicates that in nature, most milkweed doesn’t grow close enough to cornfields to be exposed to significant amounts of corn pollen. Also, Monarch larvae feed primarily on milkweed & preferentially eat milkweed without corn pollen. Furthermore, the vast majority of Bt corn now grown in the U.S. does not produce pollen that kills Monarch butterflies, so experts conclude that the risk to Monarch populations from Bt corn is low.
Greater threats to Monarch butterflies are the use of externally applied Bt and destruction of wildlife habitats by humans. Pesticides are also more likely to harm non-target insects besides the Monarch butterfly because they get into the soil and may be carried by water to non-farmland areas (2).
Resistance to Changes by 'Pests'
Through the natural process of genetic change and adaptation, it is always possible for an insect population or a plant disease strain to build up resistance to a chemical insecticide or fungicide, to a protective trait in a plant, or to any number of the techniques used to fight plant pests.
Gene products for pest control are usually more target-specific than pesticides - like vaccines compared to antibiotics. For example, Bt corn kills almost 100 percent of the corn borer and corn earworm, but traditional pesticides do not because these pests burrow into plants, where sprays cannot penetrate. The greater the number to pests that survive exposure to a pesticide, the greater the chance they will develop resistance. The pest-control mechanisms provided by genes tend to kill only insects that chew on the plant, not those in the plant’s vicinity. Externally applied pesticides kill both pests and innocent and often beneficial insects that are in the field.
Traditional pesticides have been brought to market for decades without plans in place to delay resistance. By contrast, years of research to minimize resistance has accompanied the introduction of plants modified through biotechnology.
Weed Resistance to Biotech Crops: 'Super-weeds'
The likelihood that transgenes will spread can be different for each crop in each area of the world. Gene movement depends on several factors:
- The pollination strategy of the crop
- The presence of compatible crop plants or wild relatives in the area
- The overlap of flowering times
Self-pollinating plants, such as soybeans and wheat, are less likely to spread their transgenes than cross-pollinating plants such as corn and beets. Gene movement from crop to weed through pollen transfer has been demonstrated for both wild mustards in canola and jointed goatgrass in wheat. To reduce the risk of creating 'super-weeds' it has been proposed to include linking herbicide-resistance genes to other genes which are harmless to the crop but damaging to the weed, so that the offspring of the weed that acquired the herbicide-resistance gene would not survive. Thus, spread of the herbicide resistance gene through the weed population would cease.
Outcrossing, the unintentional breeding of a domestic crop with a related plant, is considered by the USDA’s Animal and Plant Health Inspection Service (APHIS) during review of new plant varieties. The agency ensures that herbicide-tolerant or pest-resistant plants do not become plant pests themselves by outcrossing to weedy relatives. New transgenic crops will need to be evaluated on a case-by-case basis, with respect to the potential for crop-to-weed gene flow for each species in each geographical location.
Like traditionally bred plants, genetically modified plants cannot transfer traits into unrelated species in nature. If transfer of the new trait to the weed could be problematic, APHIS has the authority to halt field trials or further development of the proposed new variety. It is also important to remember that traditionally bred plants also have the potential to create weeds (2).
It is important to remember that crops produced through biotechnology are also regulated by the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA). The EPA has oversight for pesticidal properties of plants developed through biotechnology. EPA has also implemented insect resistance management requirements for biotech crops, and are required for approvals of insect-protected plant varieties(2, 9). So biotech crops, foods, and products are subjected to a wide array of environmental laws, as well as state and local regulations and standards.
What is one consumer concern regarding the environment, and how has the EPA addressed that concern?