Ecol. aspects of transgenic crops summary (fwd)

[Jim Steffens]

 I would prefer to see the data from a refereed journal than one of these
press releases.  Furthermore, I would like to see replicated studies from
more than one lab.

I suspect that Bt corn will show lower levels of postharvest infection by
Aspergillus and Fusarium than traditional corn varieties without insecticide
treatment. But that isn't what the farmer is doing.  He's either growing
corn and spraying it or growing Bt corn.

What obviously doesn't concern the American Phytopath Society is the
potential for resistance to Bt when corn borer is being challenged with
millions of acres of Bt corn.  There is already resistance to Bt in certain
lepidopterous spp., and it will not be that simple to replace the present Bt
genes with others which overcome the resistance.

Jim Steffens

> Threats To Human Health Reduced With Bt Corn Hybrids
>
> St. Paul, MN (October 18, 1999) -- The recent approval and commercial
> release of geneticallymodified, insect-resistant corn hybrids (Bt corn)
represents
> the culmination of decades of research.This innovative technology has a
distinct
> health benefit of discouraging the build up of mycotoxins in corn,
potentially
> dangerous human and animal toxins produced by fungi that cause plant
disease.
>
> Mycotoxin build up is directly related to certain fungal plant diseases,
> which can be increased by insect damage in crops. Insect larvae chew on
stalks
> and kernels, creating wounds where fungal spores can enter the plant. Once
> established, these fungi often produce mycotoxins. Some mycotoxins such as
> fumonisin, can be fatal to horses and pigs, and are probable human
carcinogens.
> "Lower mycotoxin concentrations in Bt corn hybrids clearly represent a
benefit to
> consumers," says Gary Munkvold, plant pathologist at Iowa State University
> and American Phytopathological Society member. "Studies show Bt corn
> hybrids that control European corn borer damage to kernels usually have
very little
> Fusarium ear rot, and consequently, lower fumonisin concentrations."
>
> Bt corn hybrids control feeding by the European corn borer and to some
> extent closely related insects such as the corn earworm, common stalk
borer,
> armyworm, and Southwestern corn borer. All of which cause mechanical
damage
> to the corn which influences the development of several
> crop damaging diseases including ear rots, kernel rots and stalk rots.
>
> Kernel rot caused by the fungus Aspergillus is also associated with insect
> damage to ears. Several species of this fungus produce the most notorious
> mycotoxins found in corn, the aflatoxins. "The economic impact of
aflatoxins
> has been greater than that of other mycotoxins in corn because aflatoxins
can be
> passed into milk if dairy cows consume contaminated grain," says Munkvold.
>
> Bt corn hybrids can be an important tool in the integrated management
> of corn ear and stalk rots and a boon to the environment as well. "Using
> genetically modified hybrids to control insects and diseases offers an
> alternative that is much more effective, consistent, economic and
environmentally
> sound than foliar insecticides. For example, non-Bt hybrid sweet corn
> can require 12 or more insecticide applications in a single season for the
> production of sweetcorn for fresh market sales."
>