The second most widely grown transgenic crop in the United States are maize (Zea mays) cultivars that have been engineered to express genes for various insecticidal protein endotoxins (Bt toxins) from the soil bacterium Bacillus thuringiensis. The principal target species for Bt toxin-expressing maize (Bt maize) is the European corn borer (Ostrinia nubilalis), one of the most damaging pests of maize in North America. Losses attributable to European corn borer damage exceed over $1 billion annually in the United States alone. Bttoxins are widely believed to be selectively toxic, only affecting those insects (e.g. lepidopteran larvae) that have a gut alkaline enough to activate the Bt protoxin by enzymatic proteolysis. Receptor binding by the C-terminal domain of the active toxin is the major determinant of host specificity by the differentBt toxins.

Given the growing agricultural importance of Bt maize as well as Bt cotton (Gossypium hirsutum) and Bt potato (Solanum tuberosum), it is not surprising that a storm of controversy arose following the publication in Nature of a preliminary study by Losey et al. (1999). This paper raised serious concerns about the ecological safety of Bt maize cultivation to non-target lepidopterans, in particular the larvae of monarch butterfly (Danaus plexipus). On the basis of laboratory assays, the authors concluded that monarch larvae reared on milkweed (Asclepias syriaca) leaves dusted with pollen fromBt maize ate less, grew more slowly, and suffered higher mortality than those reared on leaves dusted with nontransformed maize or on leaves without pollen.

The conclusions of Losey et al. (1999) were challenged on three grounds. First, the pollen doses used by Losey et al. (1999) were not quantitatively measured but were gauged by eye to match pollen dustings on milkweed leaves collected in the field. This raised concerns about subconscious biases on the part of the researchers. Second, concerns, as it turns out, valid ones, were raised as to the validity of extrapolating from the results of Losey at al. (1999), which concerned only one type of pollen, to all types of Bt maize pollen. Third, the soundness of extrapolating from laboratory assays to the field was uncertain, although a subsequent field study by Jesse and Obrycki (2000) did seem to confirm the fears raised by the Losey et al. (1999) study...

FROM 2001

THE MONARCH BUTTERFLY CONTROVERSY http://www.plantphysiol.org/content/127/3/709.full

GM Corn Harms Monarch Butterflies

http://abcnews.go.com/Technology/story?id=120016

Iowa State University researchers said today they found more evidence that pollen from bioengineered corn could be deadly for Monarch butterflies, prompting environmentalists to renew demands for tighter restrictions on the crop.

The Iowa study published in the journal Oecologia comes at a time when the U.S. Environmental Protection Agency has launched its own review of the safety of corn and cotton plants modified to contain a pest-fighting gene.

The Clinton administration has faced growing pressure during the past year from consumer and environmental groups, as well as some U.S. trading partners, who say not enough is yet known about the long-term safety of biotech crops. The seed industry and agribusiness contend that gene-spliced crops have undergone thousands of tests and pose no more safety risks than conventional crops....AUGUST 2014

Toxic pollen from widely planted, genetically modified corn can kill monarch butterflies, Cornell study shows

http://www.news.cornell.edu/stories/1999/04/toxic-pollen-bt-corn-can-kill-monarch-butterflies

April 19, 1999

It takes a minimum of 60 days for seeds to have a plant large enough to support a caterpillars' food needs. You can raise our tropical Milkweed in pots inside your home or greenhouse, and it should survive the winter. If you live in a northern climate and see snow, then request the Speciosia variety of milkweed seed, as it survives the winter's cold. - LiveMonarch.com

Multiple Generations
Generation 1 monarchs are the offspring of the monarchs who overwintered in Mexico. Each successive generation travels farther north. It will take 3-4 generations to reach the northern United States and Canada.- USDA.GOV

Last year we commissioned the production of 25,000 milkweed plugs of some 15 species. It was a gamble (see monarchwatch.org/blog/2013/06/the-milkweed-gamble) but this program was wildly successful and we distributed 21 thousand of the plugs in late spring and later in the fall. We have a bigger target this season. We are presently overwintering 29 thousand milkweed plugs.
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Our mission is milkweed restoration and to that end we only ship plants to ecological regions from which the seeds were obtained. This project has been supported by a large number of volunteers who have supplied seeds of many milkweed species from most areas of the country. - Monarchwatch.org

Selecting and Finding
Milkweed Plants
We have listed milkweed species, for each region
of the U.S., that we know are both valuable to
monarchs and easy to establish. While any of
these will work well in garden settings, for larger
restorations please use species that are native in
your county, and plant materials sourced as
locally as possible. You can find this information,
together with a directory of native plant vendors
that we know sell milkweed plants and / or seeds,
on our website:
www.plantmilkweed.org ==> redirect to http://monarchjointventure.org - USDA PDF