More evidence against BT
“Genetically engineered corn could harm aquatic ecosystems.” Catchy title, right? In summary, the scientists found that caddisflies, a common prey of freshwater fish, can be killed when they eat parts of transgenic corn plants that are expressing the BT toxin. This is certainly a problem, but one that has solutions.
First of all, the actual BT protein comes in many varieties, as described in this article by Virginia Cooperative Extension. Changes in the protein can change the target organism. Some can kill all caterpillars, some kill only one species. So, the most simple solution is to use a version of BT that specifically targets corn pests and not non-target organisms like caddisflies.
The article didn’t mention which types of BT were tested on caddisflies, or which types of BT are most commonly used in the fields. It doesn’t matter as much as they imply in the article anyway, as there are lots of different types of caddisflies. They eat all different things from algae to plant matter to other insects. So it is highly unlikely that all caddisfly species will suddenly decide to start eating corn leaves, especially ones that kill them. Even if they did all decide to start eating corn leaves that floated down the river, farmers could be more careful about loose leaves blowing off their land during harvest.
The problem could also be alleviated by using tissue and time specific promoters. For example, if the larvae damage corn at a specific life stage of the corn, then use a promoter that is only on during that life stage. If the pests only eat the roots, then use a promoter that only produces the protein in the roots. Or, try less strong promoters that produce the lowest level of BT possible that will still be effective against the target pest.
Finally, the research didn’t consider that overall insecticide use is decreased when BT crops are used. What is the caddisfly death rate from insecticides running off of fields compared to the number of caddisflies that are killed by eating leaves from BT corn? How many other non-target insects are killed by that run off, how many other food webs are affected? How much ground and surface water is contaminated by insecticides, how many human children are affected by the pesticides? BT has no effect on mammals, but organophosphates and other insecticides do. Not to mention the fact that BT corn sustains less fungal damage than conventional corn, leading to fewer poisonings by mycotoxins and better yields.
I don’t deny that the system needs to be perfected, but to throw BT aside based on studies such as this would be folly.