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Herbicides Affecting Monarch Butterfly Migration
(Beyond Pesticides, October 19, 2004)
The number of monarch butterflies making the annual migration from Canada and the United States to Mexico is the lowest it has been in fourteen years, experts say. This drastic decrease is apparently due in part to herbicide use, according to The Houston Chronicle.

Each fall, hundreds of millions of monarch butterflies make the trip to the area near Mexico City. This year the butterflies are funneling through a narrow 300-mile-wide strip from Oklahoma City to Del Rio before going into Mexico. Mike Quinn, a biologist with Texas Parks and Wildlife Department, stated, “We've had very few reports outside that narrow band…The biggest single report was 5,000 in San Angelo. All along Interstate 35 from Dallas, we've primarily had reports of single ones.”

Of course, weather is a very important factor in the monarch migration. A freeze last February killed many monarchs in Mexico, decreasing their numbers this year.

In addition to weather, biotechnology and herbicide use also are affecting the monarch butterflies, according to Quinn. Monarchs feed on nectar from wild milkweeds, a plant that is being killed by farmers’ use of herbicides, which has become more abundant as they are growing bio-engineered herbicide-resistant crops.

Another type of genetically engineered crop can harm monarch butterflies: those that actually contain an insecticide. Bt incorporated plants can cause adverse effects to beneficial insects that consume them. In a study published in Nature, Cornell University scientists found that monarch butterfly caterpillars are harmed by consuming Bt corn pollen dusted on milkweed. European scientists have found that beneficial insects, such as ladybugs and green lacewings, are similarly harmed. A 1997 study published in New Scientist found that honeybees may be harmed from feeding on genetically engineered canola flowers.

TAKE ACTION: Protect our land and food from genetically engineered ingredients and crops by buying USDA certified organic products. Lobby your supermarket to label GM food. Support local efforts to prohibit growing GM crops. Contact your U.S. Senators and U.S. Representative, U.S.EPA Administrator Michael Leavitt, and USDA Secretary Ann M. Veneman. For more information, see Beyond Pesticides' Genetic Engineering Page.