Letter to seed companies (7/13/1999)

I.  Summary

A number of companies have genetically engineered corn to produce in its tissues insecticidal toxins from the bacterium Bacillus thuringiensis (Bt), primarily to control European corn borers – moth caterpillars that are pests of corn. Preliminary research shows that monarch butterfly caterpillars are killed by pollen from this "Bt corn." Corn plants produce copious amounts of pollen that are dispersed by wind, and the levels of Bt corn pollen found lethal to monarchs are similar to concentrations of pollen found on plants near fields planted with Bt corn. This research suggests that the widespread planting of Bt corn may threaten monarch butterflies and other lepidoptera (butterflies and moths), including endangered species, that feed on wild plants that grow within and adjacent to cornfields. Since about 20 to 25% of US corn acreage is now planted with Bt varieties – a percentage that has grown rapidly during the past few years and that is expected to continue to grow – the threat to monarchs and other lepidoptera from Bt corn pollen could be substantial.

This petition asks the Environmental Protection Agency (EPA) to immediately impose conditions on the further planting of Bt corn and to strengthen its programs identifying and assessing the environmental risks of genetically engineered crops regulated by the Agency under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). For all varieties of Bt corn that express Bt toxin in their pollen, we ask that EPA:

1. Require that a buffer zone of non-Bt corn at least 40 to 80 feet wide (generally 16 to 32 rows of corn) be planted around fields of Bt corn beginning with the year 2000 growing season. Because most corn pollen lands close to corn plants, this measure will greatly reduce the flow of toxic pollen from Bt corn into habitats of nontarget lepidoptera.

2. Deny the reregistration of all Bt corn varieties for more than one year at a time and the registration of new Bt pesticides that are produced in corn pollen, unless and until the Agency determines, based on experimental data, that pollen from Bt corn will not be a hazard to monarchs and other nontarget lepidoptera.

3. Consult with the U.S. Fish and Wildlife Service to determine whether butterflies and moths listed as endangered or threatened under the Endangered Species Act are likely to be adversely affected by toxic pollen from Bt corn.

4. Convene a Scientific Advisory Panel to advise EPA on the ecological risks associated with genetically engineered crops used for pest control. The issues considered by this Panel should include, but not be limited to, the ecological risks from toxic pollen from Bt corn.

II.   Scientific Basis for Petition

A.   Creation and Registration of Bt Corn

To control insect pests, scientists have spliced toxin genes from the soil bacterium Bacillus thuringiensis (Bt) into corn and certain other crops, causing these genetically engineered crops to produce insect poisons in their tissues, including their pollen. Since 1995 EPA has issued conditional registrations under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA)¹ for seven Bt-based pesticides produced in corn: five for use in field corn only, one for use in field corn and popcorn, and one for use in sweet corn (see Appendix 1).²

The primary target of Bt corn is the European corn borer, a moth which, at the caterpillar stage, can cause considerable damage to a corn crop. However, the types of Bt toxins that Bt corn is engineered to produce are also toxic to many other insects from the order Lepidoptera (butterflies and moths). Since 1996, companies have marketed a number of corn varieties that have been genetically engineered to produce Bt toxins as a control for European corn borers.

Farmers have rapidly adopted this new technology. EPA estimates that in 1999, 20 to 25 percent of total corn acreage in the United States – or about 16 to 20 million acres of corn – has been planted in Bt corn varieties (EPA and USDA, 1999).

B.   Potential Impacts of Bt Corn on Monarch Butterflies and other Lepidoptera

1. Impacts on Monarch Butterflies

New research indicates that pollen from Bt corn may be extremely harmful to populations of the monarch butterfly (Danaus plexippus). Monarch caterpillars depend on leaves from milkweed, particularly the common milkweed (Asclepias syriaca), as their only source of food. In a study published in the scientific journal Nature in May, Losey et al. (1999) demonstrated in the laboratory that monarch butterfly caterpillars are readily killed by ingesting milkweed leaves dusted with pollen from Bt corn.

The toxicity of Bt corn pollen for monarch caterpillars may be of considerable significance in nature. Corn plants produce copious amounts of pollen that typically coat the leaves of wild plants growing near corn fields³ at a time when monarch caterpillars are feeding on milkweed. Thus, Losey et al.'s results indicate that monarch caterpillars living on milkweeds growing near corn fields may be killed by Bt pollen.⁴

This conclusion is supported by preliminary results from a study in Iowa. Hansen and Obrycki (1999) found that monarch caterpillars fed leaves from milkweeds growing within or adjacent to fields of Bt corn had higher mortality rates than monarch caterpillars fed leaves from milkweeds growing within or adjacent to non-Bt corn.

Monarch butterflies are renowned not only for their beauty, but also for their stamina. Monarchs make the longest migration known for any insect, covering thousands of miles (Taylor, 1999). Monarchs in the eastern half of North America migrate annually from mountainsides in central Mexico, where they overwinter, to North America, where the next generations continue moving northward as far as the southern edge of Canada. Unfortunately, monarch populations have been declining in recent years, at least in part because of logging in the butterflies' winter range in Mexico.

Toxic pollen from fields of Bt corn has the potential to considerably further diminish populations of monarch butterflies in the United States. About half the population of monarchs in the United States spend their summers and reproduce in the midwestern corn belt, in a region a few hundred kilometers wide from eastern Nebraska to Ohio (Wassenaar and Hobson, 1998). Milkweed is common in this region – an area largely comprised of intensively managed agricultural fields of corn and soybeans. Milkweed occurs along roadsides, at field margins, and even within agricultural fields, since milkweed is relatively difficult to kill with chemical herbicides (Hansen and Obrycki, 1999; Taylor, 1999). Thus, a sizable fraction of the milkweed that grows in the midwestern corn belt may grow close enough to corn to have corn pollen land on it (Losey et al., 1999).

2. Potential Impacts on Other Butterflies and Moths, Including Endangered Species

Widespread planting of Bt corn also has the potential to diminish populations of other lepidoptera that are not targeted by Bt corn. We have identified populations of the following rare butterflies as living in areas where they may suffer mortality from Bt corn pollen:⁵

We have confirmed that caterpillars of these butterflies feed on their host plants at the time when corn plants may be "silking" (i.e., producing pollen), and thus are potentially vulnerable to Bt pollen. We do not know precisely how sensitive the caterpillars of these species are to Bt pollen. However, research indicates that the early instar larvae of most butterflies are highly sensitive to Bt toxins (Peacock et al., 1998).

Other rare butterflies and moths may also be harmed by pollen from Bt corn. Rare species that may live near midwestern corn fields include:

Butterflies:

Frosted Elfin (Callophrys [Incisalia] irus)
Northern Metalmark (Calephelis borealis)
Diana (Speyeria diana)
Tawny Crescent (Phyciodes batesii)
Leonard's Skipper (Hesperia leonardus (incl. pawnee)): Pawnee's skipper
Dukes' Skipper (Euphyes dukesi)
Linda's Roadside-Skipper (Amblyscirtes linda)

Moths:

Clemen's sphinx (Sphinx luscitiosa)
Sage sphinx (Sphinx eremitoides)

EPA should assess whether these butterflies and moths feed on host plants at the time when corn plants are silking, and thus are potentially vulnerable to Bt pollen. Of particular concern, at least one population of a butterfly that has been listed as endangered under the federal Endangered Species Act – namely the Karner Blue butterfly (Lycaeides melissa samuelis) – is documented as occurring adjacent to corn fields (Andow et al., 1995). There is a strong possibility that Karner Blue caterpillars are feeding on plants at the time when corn begin to silk.⁶ With populations in Minnesota, Wisconsin, Michigan, New York, and New Hampshire (D. Andow, pers. comm.), populations of the Karner Blue are potentially at risk from Bt corn pollen.

III.   EPA has not adequately assessed the risks of Bt corn pollen to monarch butterflies and other lepidoptera

In the process of issuing conditional registrations for Bt pesticides used in corn, EPA has failed to adequately assess or address the risks of these pesticides to monarch butterflies and other lepidoptera. Although EPA discusses in documents supporting the approval of Bt pesticides (e.g. EPA, 1999) the possibility that toxin-laden pollen from Bt corn may harm Daphnia (an aquatic invertebrate), the agency fails to mention or assess the likelihood that pollen from transgenic corn would have an impact on monarchs or any other nontarget butterfly or moth species. Following extensive news coverage of the study by Losey et al. (1999), many scientists have said that the toxic effects of Bt pollen on monarch butterflies are not surprising, since the Bt toxins used in corn are known to be lethal to butterflies and to moths such as the European corn borer. EPA's failure to examine such an obvious risk is a major deficiency in a regulatory program billed around the world as thorough and comprehensive.

Particularly disturbing is EPA's apparent failure to consult with the U.S. Fish and Wildlife Service concerning the potential effects of Bt corn on lepidopteran species listed as endangered and threatened under the Endangered Species Act.⁷ Rather, EPA apparently has relied to date on a 1986 consultation with the U.S. Fish and Wildlife Service concerning the potential effect of Bt pesticide sprays⁸ on endangered and threatened species. In documents concerning conditional registrations of Bt pesticides for use in corn (e.g. EPA 1999), EPA concludes that:

A Biological Opinion was issued on December 18, 1986, concerning the possible effect of foliar spray of Bacillus thuringiensis subsp. kurstaki (Bt) on threatened and endangered species. Based on the difference in exposure scenarios between foliar Bt spray and Bt delta endotoxin expressed in corn plants, EPA believes that the Biological Opinion is not applicable and that reinitiation of consultation is not required.

EPA argues that because there are no reports of threatened or endangered insect species feeding on corn plants, the agency need not worry about the effects of Bt corn on endangered or threatened species. Obviously, this conclusion may not hold true, given the potential proximity of populations of the endangered Karner Blue butterfly to fields of Bt corn.

EPA's failure to properly assess the risks of Bt pesticides used corn is especially troubling given that Bt corn appears to offer relatively small environmental benefits. As noted previously, field corn is grown on the vast majority of U.S. corn acreage. Most field corn is not treated with insecticides for the European corn borer, the primary target pest of Bt pesticides used in corn. According to an industry plan for Bt "resistance management" for European corn borers, "[f]or the vast majority of corn acres (>90%) … growers are unlikely to treat with insecticides …."⁹ Moreover, since infestations of the European corn borer reach economic thresholds only episodically – roughly every five years – most field corn acreage is not sprayed with insecticides in most years. Thus, for the most part, Bt pesticides used on corn do not substitute for conventional chemical insecticides. This conclusion is borne out by a recent USDA Economic Research Service report (USDA ERS, 1999). This report shows that insecticide use¹⁰ against European corn borers in 1997 in the "Heartland" region of the United States (the only year and region for which data were published) was only slightly higher on non-Bt corn than on Bt corn. Insecticide use against other insect pests did not differ statistically on non-Bt and Bt corn.

In short, Bt corn has the potential to significantly reduce populations of monarch butterflies and other lepidoptera, including endangered species. However, EPA has not adequately assessed the risks to lepidoptera of Bt-pesticides that the agency has registered for use in corn.

IV.   Actions Requested by EDF

i)     Beginning with the year 2000 growing season, EPA should require the planting of a 40 to 80 foot (generally 16 to 32-row) buffer zone of non-Bt corn around all fields that are planted in corn varieties that contain Bt toxin in their pollen. This border would trap toxic pollen from Bt corn that would otherwise fall on milkweeds and other plants that serve as food sources for other butterflies and moths. As described below, certain types of Bt corn fields would be exempt from this requirement.

Rationale:

Pollen from Bt corn may pose an imminent hazard to monarchs and other lepidoptera, including rare, threatened, and endangered species. The only sure way to fully protect these creatures would be for EPA to cancel registrations of Bt pesticides produced in the pollen of corn varieties. However, EPA could greatly reduce the risk of Bt corn pollen to lepidopteran insects by requiring that a buffer zone or border of non-Bt corn be planted around the margins of corn fields. Although corn pollen can travel up to 2 miles under favorable wind conditions (EPA, 1999), about 70% of corn pollen falls within 8 meters (approximately 26 feet) of corn plants (Rice, 1999). Thus, a border of non-Bt corn would serve to "trap" toxic pollen coming from Bt corn in the center of corn fields. Pollen falling on wild plants growing near corn fields would largely come from the non-Bt corn planted in a frame around the edges of the field.

Planting such a border would not cause undue inconvenience for farmers, given the way that most corn fields are planted. Many midwestern corn farmers already plant two circles of corn around fields to create tractor turning areas. Since many farmers now use 16 row planters,¹¹ and corn rows are commonly centered at 30 inches, these borders are typically 32 rows or 80 feet wide.

Particularly in the Midwest, corn fields tend to be quite large. Fields are usually 40 acres (known as a quarter-quarter section, or a quarter mile by a quarter mile), 80 acres (a half-quarter section, or a half mile by a quarter mile), or 160 acres (a quarter section, or a half mile by a half mile). Thus, 16 to 32 row borders around midwestern corn fields would be wide enough to protect lepidoptera feeding on plants growing near corn fields, but small enough to allow farmers to plant considerable acreage in Bt corn should they wish to do so.

Moreover, the non-Bt borders could count towards farmers' "refuge" requirements – areas of non-Bt corn that farmers will need to plant in the year 2000 growing season to comply with resistance management plans for Bt corn. (EPA and the Bt corn industry have not yet finalized the specifics of these resistance management plans.)

For reasons of practicality, Bt corn in Natural Resource Conservation Service-approved contour strip cropping systems should be exempt from planting borders of non-Bt corn. In addition, small corn fields for which a 40 foot border would exceed the refuge requirement for Bt corn should be exempt from planting borders of Bt corn,¹² unless endangered, threatened, or rare butterflies inhabit the area. These exemptions would mean that many farmers outside the midwestern corn belt – where corn is often planted in far smaller fields and a smaller percentage of land is planted with corn – would be exempt from planting borders of non Bt corn.

ii)     EPA should not extend registrations of existing Bt pesticides for use in corn for more than one year at a time, or register any new Bt pesticides that are produced in corn pollen, until the agency determines, based on experimental data, that the pollen produced by fields of corn containing Bt pesticides will not pose a danger to monarch butterfly populations or populations of rare, threatened, or endangered lepidoptera.

Rationale:

All of the Bt-pesticides now used in corn varieties currently on the market were approved under temporary registrations that will expire in either the years 2000 or 2001 (see Appendix 1). EPA should not renew these registrations for more than one year at a time or issue new ones until the agency can be confident that these pesticides will not harm populations of nontarget lepidoptera.

iii)    EPA should enter into consultation with the U.S. Fish and Wildlife Service to determine whether any butterflies or moths protected under the Endangered Species Act as endangered or threatened are likely to be adversely effected by toxic pollen from Bt corn.

Rationale:

EPA apparently has not complied with the Endangered Species Act's requirement to consult with the U.S. Fish and Wildlife Service when federal actions affect populations of federally listed threatened or endangered species. Based on the information set forth in this petition, EPA should promptly initiate consultation with the U.S. Fish and Wildlife Service with regard to impacts of Bt corn on Karner blue butterflies, and should review whether any additional endangered or threatened species may be affected by Bt corn.

iv)     EPA should convene a Scientific Advisory Panel to advise EPA on the ecological risks associated with genetically engineered crops used for pest control. This Panel should be composed largely of experts on conservation biology and ecological risk assessment. The issues considered by this Panel should include, but not be limited to, the ecological risks from toxic pollen from Bt corn. The Panel should also consider risks associated with other types of genetically engineered crops and advise EPA on how to improve the agency's protocols for assessment of ecological risks.

Rationale:

EPA has clearly failed to adequately assess the ecological risks associated with Bt corn. The agency should convene a Science Advisory Panel to advise the agency on the magnitude of the risks associated with Bt corn and on ways to avoid or mitigate these risks.

Although the risks associated with Bt corn pollen should be the Panel's first priority, EPA should also use the Panel to consider other ecological risks from crops genetically engineered for pest control. For example, some experts believe that corn and soybeans genetically engineered to tolerate applications of synthetic chemical herbicides may pose a threat to populations of monarch butterflies (Taylor, 1999; Wassenaar and Hobson, 1998). Milkweeds plants are now relatively common in corn and soybean fields because they are relatively resistant to herbicides. However, the more aggressive weed control made possible through use of herbicide-tolerant crops may allow farmers to kill milkweeds growing in agricultural fields, thus reducing considerably populations of host plants in the Midwest available for monarch butterflies.

EPA's failure to consider the effects of toxic pollen from Bt corn on lepidoptera indicates serious flaws in the agency's protocols for assessing ecological risks associated with genetically engineered crops. For example, EPA considered the effect of Bt pollen on Daphnia (an aquatic invertebrate unlikely to be affected by Bt toxins) but failed to consider the effects of Bt corn pollen on the most obvious category of potential victims – nontarget lepidoptera. EPA should obtain advice on how to improve the agency's ecological risk assessments.

Endnotes

1. 7 U.S.C. 136 et seq.

2. Field corn, which is used for animal feed and processed corn products such as corn syrup and ethanol, constitutes the vast majority of corn planted in the United States. In contrast, sweet corn and popcorn – types of corn consumed directly by humans – account for a very small percentage of US corn acreage. In 1992 (the latest year for which USDA posts final acreage estimates), about 80 million acres of field corn were planted in the United States, compared to only 250,000 acres of sweet corn (http://usda/mannlib.cornell.edu/data-sets/).

3. Corn produces copious amounts of pollen because it is a wind-pollinated plant. In other words, corn plants depend on the vagaries of the wind to carry pollen from one plant to another. In contrast, insect-pollinated plants (including cotton and potatoes, some varieties of which have also been genetically engineered to produce Bt) produce much less pollen because insect pollinators carry pollen directly from flower to flower.

4. Most of the Bt-pesticides used in corn are produced in corn pollen. However, according to company data submitted to EPA, at least one Bt pesticide – Cry1Ac registered by DeKalb Genetics – is not produced in corn pollen (EPA, 1998).

5. These species are classified as critically imperiled, imperiled, or vulnerable throughout their range by The Nature Conservancy and the Natural Heritage Network.

6. See http://www.fws.gov/r3pao/eco_serv/endangrd/news/karnerbl.html

7. 16 U.S.C. 1536

8. Non-genetically engineered Bt toxins used in topical sprays have been registered as pesticides for several decades.

9. Monsanto et al., "Industry insect resistance management plan for Cry1A plant-expressed protectants in field corn," submission to EPA, April 19, 1999. The prospect that insect pests will evolve resistance to Bt toxins used in Bt crops is a grave concern, since Bt toxins are among the safest insecticides to humans. A major component of the strategy to slowing the evolution of resistance pests is to have farmers planting Bt corn also plant of "refuges" of non-Bt corn. These refuges produce insects pests that are susceptible to Bt toxins and can mate with any resistant pests that emerge from Bt corn fields. Monsanto et al. argue that "refuge" sizes for Bt corn need not be especially large, because farmers generally do not use insecticides on field corn and thus refuges would be unlikely to be treated with insecticides that would kill Bt-susceptible insect pests.

10. Insecticide use was measured in acre-treatments. An acre-treatment is the number of different pesticide active ingredients applied per acre times the number of repeat applications.

11. Some farmers use four-row planters.

12. Of course, farmers would still be required to plant refuges for resistance-management purposes.

Appendix 1. Bt Pesticides for Use in Genetically Engineered Corn*