Bt pollen and the little guys

[Paul Cherubini]

Roger Johnsen wrote:

> The evidence appears to be that it's dangerous in the field planted with BT
> corn because the concentration of BT pollen on milkweed is very high, but not
> 10 m away from the field.

However, the EPA Fact Sheet on Monsanto's popular Yield Guard Bt corn 
indicates the actual concentration of Bt protein (the actual toxin) in the Bt corn
pollen is very low.

Dr. Sear's said in his report:  "The actual threat to the Monarch butterfly can only
be determined by assessing the dosage that affects the larvae and their 
degree of exposure to Bt-corn pollen in the field," 

Sear's study did a great job evaluating the dosage aspect, but did not address
the crucial question of real world field exposure. In other words, amazingly,
none of the researchers to date has documented whether or not monarch butterfly
caterpillars developing on Asclepias syriaca milkweed growing within corn
fields ever die from it.

I'm puzzled why Monsanto apparently didn't make real world exposure and mortality
measurements (if there is any mortality) tests a priority last summer.

Perhaps there were logistical difficulties involved; i.e. it might be tough to find
A. syriaca growing within a tall, dense stand of corn in mid-late July (the Bt corn 
pollen shedding period) because this milkweed is not common in corn fields
in mid-late summer. And it might be even tougher to locate monarch eggs and caterpillars
on that milkweed since female monarchs are not known to routinely crawl
down through a dense canopy of tall vegetation to lay eggs on buried milkweed plants.

Asclepias syriaca is abundant at the edges of cornfields, however, and Dr. Sear's
research has shown the amount of pollen on those milkweeds is low and rapidly
degrades or is blown away by the wind or washed off by the rain.

Paul Cherubini