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Bacillus thuringiensis (Bt) Plant-Incorporated Protectants - page 9 / 30





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Bt Plant-Incorporated Protectants October 15, 2001 Biopesticides Registration Action Document

Limited data do not indicate that Cry proteins have any measurable effect on microbial populations in the soil. Horizontal transfer from transgenic plants to soil bacteria has not been demonstrated. Cry1Ab protein bioactivity from Cry1Ab corn tissue added to the soil decreased with an estimated DT50 (Degradation Time) of 1.6 days and an estimated DT90 of 15 days. The bioactivity of purified C r y 1 A b p r o t e i n i n s o i l d e c r e a s e d w i t h a n e s t i m a t e d D T 5 0 o f 8 . 3 d a y s a n d a a n e s t i m a t e d D T 9 0 o f 3 2 . 5 d a y s . T h e b i o a c t i v i t y o f p u r i f i e d C r y 1 F p r o t e i n i n s o i l d e c r e a s e d w i t h a n e s t i m a t e d D T 5 0 o f days. 3 . 1 3

b. Bt Cotton

EPA has also reviewed the original data base and the new data, information, and comments regarding ecological effects for Bt cotton. EPA has reviewed the potential for gene capture and expression of the Cry1Ac endotoxin in cotton by wild or weedy relatives of cotton in the United States, its possessions or territories. EPA has concluded that there is a possibility for gene transfer in limited geographic locations where wild or feral cotton relatives exist. This transfer is of concern because 1) traits which enhance the survival, invasiveness or adaptability of a plant have the potential to increase the frequency of that trait (allele) in the recipient population and result in a shift in community dynamics (e.g., species abundance, distribution) for multiple species, 2) the native genome of any wild species is effectively altered by the introduction of an adaptive trait (e.g., resistance to insects, diseases, stress) and a net loss in the biodiversity of the recipient species may occur as alleles or even biotypes of the species are lost through this genetic introduction and selection, and 3) wild or feral species which are genetically compatible with crop plants and other non-domesticated plant species, and are recipients of novel traits, may transfer these traits in a reciprocal fashion to these related species in subsequent generations. Therefore, EPA has imposed restrictions on the planting of commercial cotton in southern Florida, Hawaii, Puerto Rico, and the U.S. Virgin Islands. In addition, restrictions to prevent gene flow have been imposed for test plots and breeding nurseries in Hawaii and Puerto Rico although the registrant may provide data which will allow EPA to ease or remove these restrictions in the future.

The Agency has concluded that the weight of evidence indicates no unreasonable adverse effects of Cry1Ac protein expressed in cotton to non-target wildlife or beneficial invertebrates. EPA further believes that cultivation of Cry1Ac cotton may result in fewer adverse impacts to non-target organisms than result from the use of chemical pesticides. However, EPA is requiring insect census estimates from representative fields to determine if there are long-term adverse impacts from the use of Bt cotton and field tests of Cry1Ac protein accumulation and/or persistence in soil under a range of conditions typical of Bt crop cultivation as confirmatory data.

In the ecological effects testing done, no treatment related effects were observed in Bobwhite quail fed Cry1Ac cottonseed meal as part of their diet. No measurable deleterious effects from the Cry1Ac protein on honey bee larvae, honey bee adults, parasitic wasps, Ladybird beetles, green lacewings and Collembola (springtails) were observed in submitted studies. The larvae of endangered Lepidoptera species in cotton growing counties (Quino Checkerspot butterfly, Saint


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