April 05, 2020

An earful of questions about transgenic corn

On Dec. 12, Maine became the first state in the nation to deny registration of three varieties of genetically altered field corn designed to produce their own pesticide to control the European Corn Borer (ECB). This action by the Board of Pesticides Control was compelled by Maine statutes which place the burden on companies seeking to register a new pesticide to demonstrate that a need exists for the product and that the product will not cause “unreasonable adverse effects on the environment.” There is no doubt that the applicants, DEKALB Genetics and Novartis Seeds, failed to meet either of these burdens, after two appearances before the board, which I attended.

Douglas Johnson’s characterization (BDN commentary, Dec. 31) of those who raised questions about the transgenic products at these meetings as “Luddites,” and of the Board of Pesticides Control as “muddleheaded bureaucrats,” is neither constructive, nor accurate, nor good public relations (Johnson was identified as a partner in a biotechnology public relations firm in Stonington).

The opposition to the transgenic products in Maine has nothing to do with, as Johnson put it, “fanciful scenarios for genetic mayhem should the Bt gene somehow escape from the corn.” Johnson appears to be referring to the demonstrated risk of gene transfer through cross-pollination, causing wild, weedy relatives of the genetically modified plant to acquire some of the characteristics of the modified plant. This is indeed a concern, particularly in Mesoamerica, where weedy relatives of maize abound, and when transgenic crops are designed to be herbicide resistant, hence potentially transferring that resistance to weeds. The focus of the concerns here, however, was on quite a different issue: the impact of use of varieties of corn which produce their own Bt pesticide on the development of pest resistanct to Bt sprays.

Bt (shorthand for the aerobic, spore-forming bacterium Bacillus thuringiensis commonly found in soils) produces a number of insect toxins, which have been incorporated in foliar sprays for decades. Because these toxins are developed from a naturally occurring bacterium, and are very safe for human beings, animals and non-target insects, they are some of the few pesticidal products available for use by organic as well as conventional farmers. They are effective against a variety of pests, including the Cologado Potato Beetle. Because of Bt’s effectiveness and safety compared to the synthetic chemical pesticides it displaces, Bt was characterized as the “single most important insecticide ever discovered,” in the Sept. 16, 1997, EPA rulemaking petition filed by an international coalition of organic growers and environmental organizations, calling for the cancellation of registration of all transgenic Bt plant pesticides.

Johnson, who characterizes organic farmers as “Luddites,” might be surprised to learn that many Bt products used by organic farmers have in fact been produced through genetic engineering. It is not the use of genetic engineering per se which is opposed by many Maine organic farmers, but rather the risks presented by the release of live transgenic organisms in the field.

When Bt is used as a foliar spray, its application can be targeted to the appropriate parts of the plant, and it naturally degrades in a few days. It kills some, but not all, of the Bt-susceptible insects. By contrast, genetically engineered Bt plants express Bt throughout the plants for their full life cycle. They are designed to, and do, kill virtually all Bt-susceptible insects. The only insects which survive to produce new generations of pests are those which have the trait of resistance to the Bt. The threat of insect resistance, an ever present reality of the “pesticide treadmill,” is many times escalated. Such a threat is hardly “fanciful.” The tobacco budworm, a cotton pest, has been shown to become 10,000 times more resistant to Bt after three years of exposure to Monsanto’s transgenic Bt cotton Bollgard.

At the board’s first meeting on the transgenic corn applications, Novartis representative Jeff Stein acknowledged that if widespread use of Bt corn develops in the field, it is likely to place “high selective pressure” on the ECB to become tolerant to the Bt toxins. Stein also admitted that there were many unanswered questions about how to prevent the development of resistance. EPA has not yet approved a resistance management plan for the Bt corn, and EPA registration is conditional on development of such a plan by the year 2000. As Stein admitted, according to the EPA, “so much is not known that it would be premature to come out with a (resistance) strategy now.” The conditional registration is designed to “fill in the knowledge gaps” to study such issues as “insect growth, migration behavior, mating.” Stein also acknowledged that when a method to scientifically manage against resistance is developed, practical questions exist about how to ensure that all farmers carry out these measures.

Concerns about resistance management merged in the Board of Pesticides Control’s deliberations with serious doubts about the need for the transgenic field corn products in Maine. Unlike the transgenic “NewLeaf” potato previously approved in Maine, these products will not replace other, more hazardous pesticides currently used to control target pests. On the contrary, all indications are that no field corn growers in Maine use any pesticides to control the ECB. While the ECB may impair the quality and quantity of corn kernels on the husk, no one has yet demonstrated that it significantly impacts the overall yield of corn silage crops in Maine — where the entire plan is harvested and ground up for fodder.

The board challenged the applicants to produce evidence of such impact by the Dec. 12 meeting, and they failed to do so. The testimony of a certified crop advisor for an ag supply dealer that his certification “makes me a scientist, and I can tell you I have seen corn borer damage” referred to by the opponents. Of far more weight were the comments of the Cooperative Extension corn pest specialist Don Barry, who found the applicants’ claims of increased silage yield “hard to believe without any date,” and who opined that “the lover we can limit (transgenic Bt crops’) dissemination, the longer Bt’s going to be useful for everyone.

As a result of the biotech companies’ inability to produce the evidence required by Maine’s registration statute, in the words of Board of Pesticides Control member Alan Lewis, the board had “the luxury of making Maine not participate in this experiment.” That was the prudent, and the necessary, decision.

Sharon S. Tisher, who teaches environmental law at the University of Maine in Orono, has served as a member of Maine’s Commission to Study Biotechnology and Genetic Engineering and is chair of the Public Policy Committee of the Maine Organic Farmers and Gardeners Association.

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