Has The EPA Failed The Caddisfly With GMOs?

The caddisfly (Trichoptera order = hairy legged) are moth like insects, with long thin bodies and two equally long antennae protruding from its head (not to confuse it with a stonefly, another common aquatic insect, that has three antennae).

Like most insects, caddisflies are part of the world's giant, natural interconnected waste processing system - they munch on dead plant debris and turn it into smaller dead plant debris (and so on by other organisms).

According to a recently published article in PNAS, an unconsidered threat to the caddisfly has come to pass - genetically modified corn (i.e. a genetically modified organism, GMO).  The corn strain, called Bt corn, was genetically modified to contain a gene from the naturally soil-inhabiting bacterium Bacillus thuringiensis which kills lepidoptera larvae. [source]

The gene insert in Bt corn was originally targeted at the European Corn borer (for obvious reasons).  However, when the Environmental Protection Agency (EPA) assessed the environmental impact of Bt corn toxins (pdf here), they were primarily concerned with gene transmission of GMO strains to wild type strains, and effects of Bt corn toxins on land.


And so reads the EPA report, "...even though EPA knew that Bacillus thuringiensis var. kurstaki was toxic to Lepidoptera, EPA also concluded that threatened or endangered species of butterflies and moths would not be at risk because they would not be exposed to Bt Cry1protein in Bt crops." [source: page IIC32]

Furthermore,  "The major source of Bt Cry proteins in fresh water would be corn pollen" [page IIC32].  According to the EPA report, the amount of pollen that would enter freshwater systems would be ~100 times lower than any significant toxic effects observed in lepidptera thus far.

However, a significant portion of organic matter located within corn fields can move into the local freshwater systems via run-off and rain.  The result - Bt corn toxins killing non-target lepidopterans down stream.


The research team addressed three issues the EPA failed to:

• Entry of Bt corn plant parts EITHER than pollen into local streams - found them; storm surges carry Bt plant tissue farther down stream
• Is Bt pollen eaten by caddisflies in the field - yes
• Does the Bt toxin harm caddisflies in the lab? - yes

Thus, although direct evidence for the effect of BT toxins on non-target organisms remains to be observed (i.e. measuring the effects of Bt toxin naturally found in streams on naturally present caddisflies), the PNAS study stresses the importance of fully evaluating the impact GMO crops will have on the environment.

This is especially true, given ~35% of corn in the USA is currently Bt corn, and similar Bt strains have been created for cotton, potatoes, and sweet corn.

Interestingly, this study comes 6 years after a Canadian led team of scientists evaluated the potential impact of Bt corn on monarch butterflies (another lepidopteran).  However, the study focused on land-dwelling monarchs, and not aquatic lepidopterans, "This 2-year study suggests that the impact of Bt corn pollen from current commercial hybrids on monarch butterfly populations is negligible." [source]

So, has the EPA let down the caddisfly?  According to Jennifer Tank, a member of the aquatic research team, yes, ""As part of the licensing process for genetically modified crops, the U.S. Environmental Protection Agency (EPA) was responsible for testing and identifying potential environmental consequences from the planting of Bt corn," says Jennifer Tank..." [source]