Monsanto

Bt Corn: Environmental Safety And The Monarch Butterfly

"Bt corn" refers to corn that has been enhanced, through plant biotechnology, by a trait that protects it from damage against specific insect pests. Due to a protective protein that the corn produces, it is not damaged by insects such as the European corn borer, which can have devastating and irreversible effects on corn crops.

Prior to the introduction of Bt corn, farmers typically controlled insect pests with conventional insecticides that killed damaging insects, as well as the beneficial and desirable insects (e.g., those that help control other pests that harm plants or spread plant diseases). An important advantage of Bt corn is that insecticide sprays are either reduced or eliminated; as a result, the effects on beneficial and other non-target insects also are dramatically reduced or eliminated. By reducing the use of broad-spectrum insecticides, Bt corn reduces the potential to harm non-target and beneficial species, and it reduces the impacts of agricultural inputs on the environment in general.

Nature article

The May 20 issue of the journal Nature reports on a laboratory study conducted by Cornell University researchers that asserts a negative impact of milkweed dusted with pollen from Bt corn on the growth and survival of the non-target Monarch butterfly.

Monsanto is very aware of the research on Monarch butterflies and other non-target species, as well as on beneficial insects that help control pests in fields. Considered in total, research conducted in the field supports the safety of Bt crops for beneficial and other non-target insects. The laboratory study in Nature provides interesting information, but reflects a situation very different than that actually prevalent in the natural environment. The principal author of this laboratory study has cautioned against drawing conclusions until more research and data have been collected and studied.

Monarch larvae feed almost exclusively on milkweed. The milkweed habitat preferred by monarchs is prairies, fields and roadsides, not the middle of full grown and pollinating corn fields. In real life situations, the exposure of monarch milkweed habitat to corn pollen is very low because only a very small portion of these milkweeds grow in close enough proximity to corn fields for exposure to corn pollen. And in the instances where pollen exposure occurs, experts predict little impact on monarch larvae beyond the edges of Bt corn fields. Most corn pollen remains within the corn field and monarch larvae can choose to avoid feeding on Bt pollen by feeding on the underside of leaves or on other milkweed leaves with little or no Bt pollen. In addition, there is little overlap between the periods during which pollen is shed from corn and the periods when monarch larvae are feeding. This information supports the conclusion of a very low likelihood of effect of Bt pollen on non-target insects like the Monarch butterfly in their natural habitats.

Monsanto is very supportive of initiatives that lead to better understanding of insect-protected crops and non-target and beneficial insects. To that end, we are participating in an industry effort to support additional field research on the impact of Bt crops on these insects in their natural environment. We will continue to cooperate with researchers and the industry to support studies aimed toward better understanding of insect-protected crops.