Bt transgenic crops were first registered in the USA by the United States Environmental Protection Agency (USEPA) in 1995. The first commercial plantings were made in 1996 with less than 1% being planted each to corn (aprox. 161, 943 ha) and potato (aprox. 4,049 ha) and 14% to cotton (aprox. 728,745 ha). By 1998 these numbers had grown to 17% for corn (aprox. 4,858,300 ha), 3% for potato (aprox. 20,243 ha), and 17% for cotton (aprox. 931,174 ha). USA Bt corn plantings for 1999 are projected at 20-25 (aprox. 6,283,400 - 7,854,251 ha) of the total corn plantings (31,417,004 ha). To date, three Bt toxins have been incorporated into commercial corn and registered in the USA by USEPA. These include Cry1Ab, Cry1Ac, and Cry9C. The events associated with these incorporations include Event 176 (Novartis, KnockOut^®; Mycogen, NatureGard^®), BT11 (Novartis, YieldGard^® and Attribute^®), MON810 (Monsanto, YieldGard^®), DBT-418 (DeKalb/Monsanto, Bt-Xtra^®), and CBH-351 (AgrEvo/PGS, Starlink^®).
One of the major issues associated with the extensive use of Bt corn is the potential for resistance to develop in the European corn borer (ECB), Ostrinia nubilalis Hübner, population. As a result of the recommendation of a Scientific Advisory Panel (SAP), the USEPA has instituted a 20% refuge requirement beginning in 2000 (50% if corn and cotton are planted in the same area, primarily for managing resistance in corn earworm/cotton bollworm, Helicoverpa zea (Boddie)). For ECB, Bt fields must have non-Bt corn within a 0.4 km according to these new regulations. This SAP panel was made up of individuals from registrants, academia, and public interest groups. Another issue of concern is the acceptance of Bt corn in foreign markets. It is still unclear as to how this will be resolved, but some markets are, and possibly will be closed to raw and processed commodities from these transgenics. Ethical issues associated with the broader area of genetically manipulated plants and animals (GMO’s) also bring a degree of uncertainty to the future of Bt and other transgenics. No doubt, Bt corn and on a larger scale GMO’s are and will change our lives. One can only hope that these will be positive changes and that these organisms will be developed and used responsibly. It is imperative that these be adequately tested/evaluated prior to their release and use.