jal_ut wrote:Unfortunately the caterpillars we want to keep off our plants are the immature stage of butterflies. Does that make butterflies the enemy?
About Monarch butterflies. The worms feed on milkweed plants. The problem seems to come when pollen from the Bt corn drifts over on some milkweed plants where the monarch's worms feed. In this area, I don't see that as any big problem since monarchs are not very common. Neither is milkweed. Nor is corn a major crop. For the small plot a home gardener may plant, it seems the risk to monarchs is nil. It may be a different in corn growing country? Bt is a naturally occuring organism. I would rather take my chances with that than some of the chemicals sprayed on corn on the large farms.
I did a report on whether or not Bt corn is having an effect on Monarch populations. And you're exactly right, the concern is about the protein being present in pollen that drifts and lands on milkweed plants, which Monarch larvae accidentally eat.
There was a huge concern about this in the late 90's and early 00's, and because of that, a national group was formed to study its effects. Of the dozen or so articles we read for the report, they all agreed that Bt pollen could in fact kill Monarch larvae.
However, the amounts it took to kill monarch larvae were incredibly high. We're talking the milkweed leaves would have to be literally covered in Bt pollen, like fuzzy yellow. None of these levels is even close to what is found in fields, even if the milkweed plant is growing between rows.
I would argue that Bt corn is actually safer than (organically certified) Bt dusting and granular formulas, as it can't be blown off the plants by wind onto surrounding plants. Housing the Bt within the plant selectively kills only the insects (like European Corn Borer) which feed on the plant, and the amount of pollen drift is negligible.
The report below documents another unintended consequence of the planting of GMO crops such as Bt corn - namely the contamination of waterways with the Bt protein (Cry1Ab) that is intended to kill insects, especially Lepidoptera that attempt to feed on the stems, foliage, roots or ears of the corn. The GM engineered protein, as you will see, has been found in waterways but how did it get there? Is it through direct runoff from fields that have been harvested? Is it from roots that extrude the protein in the process of controlling rootworms? Or, is it from the breakdown of corn tissues that results in the formation of a dust containing the protein that eventually makes its way to the water courses? All three avenues of contamination may be occurring. However, if the Cry1Ab protein is airborne and in sufficient quantities on the surfaces of foliage, it may well be contributing to mortality of Lepidoptera and in some cases beetles well outside the boundaries of the corn fields. Clearly, more work is needed to determine if the escaped Bt protein is a hazard to non-target insects, either in the aquatic habitats or on land.
To be fair, I've never seen a study on the Bt toxin protein leaching, so it could be possible. However, I think it's far more likely to break down quickly after it leaves the plant, since it is an organic compound and Bt toxin dusts break down fairly quickly as well.
And they need to check their facts, because I'm not exactly sure what this is talking about: "it may well be contributing to mortality of Lepidoptera and in some cases
beetles."
I'm pretty sure the Bt toxin inserted into Bt corn has zero toxicity against
Coleoptera (a completely different Order than Lepidoptera). Now, there are Bt toxins that kill Coleoptera, but none that I know of that are modified into corn genomes. Corn doesn't have a huge amount of pest pressure from beetles at least not on the scale of EAB. Big seed companies like Monsanto wouldn't find it profitable to spend the money inserting Bt toxin effective against Coleoptera, as far as I can guess.