Bt insect protection of crops and honey bees

re genetically modified crops to blame for the declining number of bees? This is the question many have been asking for the last few days. Some scientists from France have allegedly determined that Baccillus Thuringiensis, a bacteria normally found in the soil,and which has been widely used to develop various genetically modified crops, is behind deaths of honey bees in the United States and elsewhere. Not many people have bought their findings. In fact, today, GMO Pundit a.k.a David Tribe posted an article by three researchers -Eric Sachs, Yong Gao and Jian Duan - that argues to the contrary. Here is the full article, entitled, ” Bt insect protection of crops and honey bees.”

Summary

–Entomologists have not been able to determine the cause of CCD (colony collapse disorder) in honey bees. While the cause is not yet clear, there is strong evidence that the production of specific insecticidal proteins from the soil bacterium Bacillus thuringiensis (Bt) in crops to control targeted caterpillar pests and beetles does not pose a risk to honeybees.

–There is extensive information on the lack of non-target effects to diverse groups of beneficial insects including honey bees and other pollinators from Bt microbial preparations that contain Bt proteins.

–Bt proteins are ideal for use in organic production and in Bt crops because they bind specifically to receptors on the mid-gut of sensitive caterpillar pests and have no deleterious effect on beneficial/non-target insects under the conditions of use, including predators and parasitoids of targeted caterpillar pests and honeybees.

–Scientists perform extensive honeybee safety assessments on all insect-protected crops, including Bt corn and Bt cotton. The Bt proteins in these crops have been shown to have no adverse effect on the honeybee..

–EPA risk assessments have demonstrated that Bt proteins expressed in Bt crops do not exhibit detrimental effects to non-target organisms in populations exposed to the levels of Bt proteins produced in plant tissues.

–Specific studies involving Cry1Ab provide strong evidence of the safety of MON 810 Bt corn to the honeybee (similar studies have been conducted with other Bt proteins in genetically modified crops).

–The EPA concluded that based on the weight of evidence there are no unreasonable adverse effects of the Cry1Ab protein expressed in MON 810 Bt corn to non-target wildlife or beneficial invertebrates.

Colony Collapse Disorder in Honey Bees

Because honey bees play such a crucial role in agriculture, the recent news that large areas of the U.S. were experiencing a wide-spread sudden loss (or disappearance) of honey bee colonies caused alarm across the country. This phenomenon has been described by honeybee experts as Colony Collapse Disorder (CCD). Groups critical of the widespread adoption of biotech crops in the U.S. and globally have recently begun a campaign alleging that CCD may be caused by crops expressing one or more Bt proteins. Unfortunately, entomologists have not been able to determine the cause of CCD. While the cause is not yet clear, there is strong evidence that the production of specific insecticidal proteins from the soil bacterium Bacillus thuringiensis (Bt) in crops to control targeted caterpillar pests and beetles does not pose a risk to honeybees.

Safety of Commercialized Bt Proteins in Corn and Cotton

There is extensive information on the lack of non-target effects to diverse groups of beneficial insects including honey bees and other pollinators from Bt microbial preparations that contain Bt proteins. The Bt proteins produced in Bt corn and Bt cotton are present in microbial products used in agricultural systems to control targeted pests. Bt proteins are extremely selective and are toxic only to specific pests . A generalized mode of action for Bt proteins includes ingestion of the protein crystals by insects, solubilization of the crystals in the insect midgut and proteolytic processing of the released Bt protein by enzymes, and binding of the partially digested “activated” protein to specific high-affinity receptors on the surface of the midgut epithelium of target insects . Bt proteins are ideal for use in organic production and in Bt crops because they bind specifically to receptors on the mid-gut of sensitive caterpillar pests and have no deleterious effect on beneficial/non-target insects, un

Safety Assessment of Bt Crops

Scientists perform extensive honeybee safety assessments on all insect-protected crops, including Bt corn and Bt cotton. The Bt proteins in these crops have been shown to have no adverse effect on the honeybee. EPA evaluated studies of potential effects on a wide variety of non-target organisms that might be exposed to the Bt protein, e.g., birds, fish, honeybees, ladybugs, parasitic wasps, lacewings, springtails, aquatic invertebrates and earthworms. Such non-target organisms are important to a healthy ecosystem, especially the predatory, parasitic, and pollinating insects . These risk assessments demonstrated that Bt proteins expressed in Bt crops do not exhibit detrimental effects to non-target organisms in populations exposed to the levels of Bt proteins produced in plant tissues.

To illustrate how the different Bt proteins produced in Bt crops are evaluated for safety to the honeybee, two representative studies are described below for the Cry1Ab protein produced in MON 810 Bt corn. These studies with Cry1Ab protein were conducted with the trypsin-resistant core because this is the insecticidally-active portion of the Cry1Ab protein. Specific studies designed to assess the potential for adverse effects to developing larval and adult honeybees are described below.

Honeybee Larva.

The primary route of exposure for honey bee larvae to the Cry1Ab protein is ingestion of pollen collected by foraging adults from genetically modified plants. Therefore, honey bee larvae were exposed to Cry1Ab protein in their natural diet by including a maximum hazard dose (20 parts per million in distilled water mixed with honey) in developing brood cells. This maximum nominal concentration of 20 ppm was approximately 100 times greater than the maximum expected Cry1Ab protein level in MON 810 pollen. In addition to this treatment group, a negative control group was treated with distilled water. Another control group was treated with heat-attenuated (inactivated) Cry1Ab protein (20 ppm), and one set of larvae received no treatment (untreated control). At least 50 bees (1 to 4 days old) were in each replicate, and there were three replicates for each group. The treatments were administered to each larval cell through an electronic micro-applicator, which delivered 5 microliters (?L) of the test diet.

There were no statistically significant (P>0.05) differences in honeybee larval survival to adult emergence among the four treatment groups. The mean adult survival rates after emergence ranged from 91.7% to 96.0% across all groups, including the controls and Cry1Ab-treated groups. This study demonstrates that honeybee larvae were not adversely affected after being exposed to Cry1Ab protein at a concentration of 20 ppm in their diet.

Adult Honeybee.

Adult bees reared in bee hives were immobilized using CO2. The test diet was prepared by mixing the appropriate amount of the insecticidally-active Cry1Ab protein with a honey-water (50-50) syrup to a concentration of 20 parts per million (?g protein/g diet; ppm). The negative control group was fed the same diet with the exception that no Cry1Ab protein was added to the honey-water mixture. A second control group was fed heat-attenuated (inactivated) Cry1Ab protein at the same concentration (20 ppm) as the treatment group. A fourth test system was an empty cage to measure the amount of diet loss due to evaporation. All diets were presented to the bees in a 6 ml shell vial inserted through a cork in the holding cage lid. Three replicates of four test groups of at least 40 adult honeybees were selected and placed in each holding cage. Two observations were made the first day and were made daily for the duration of the 9-day study. At the time of the daily observation, the test diets were replaced with fre

Adult honeybees exposed to the Cry1Ab protein in a honey-water solution for 9 days at a concentration of 20 ppm showed no signs of treatment-related mortality or toxicity. At the end of the testing period, the mortality percentage was calculated for each group. Mortality in the treatment and the negative control groups was 16.20% and 22.28%, respectively. The heat-attenuated control group mortality was 32.59%. Mortality showed a sharp increase in all three groups from days 6 through 9. At the termination of the test, the highest mortality was observed in the group that was fed the heat-attenuated Cry1Ab protein diet, while the lowest mortality was observed in the group that was fed the Cry1Ab protein diet. The mortalities in the treatment group are not considered to be treatment-related because the two control groups showed a higher percentage of mortality over the same time interval. There was no significant statistical difference (P>0.05) in mortality patterns between any of the groups.

The EPA concluded that based on the weight of evidence there are no unreasonable adverse effects of the Cry1Ab protein expressed in MON 810 Bt corn to non-target wildlife or beneficial invertebrates . They reported no measurable deleterious effects were observed in submitted studies of the Cry1Ab protein administered to honey bee larvae, honey bee adults, parasitic wasps, Ladybird beetles, green lacewings, Collembola (springtails), and Daphnia.

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1. Wolfersberger et al., 1986; Hofmann et al., 1988a; Hofmann et al., 1988b; Van Rie et al., 1989; Van Rie et al., 1990

2. Dulmage, 1981; Klausner, 1984; Aronson et al., 1986; Whiteley and Schnepf, 1986; MacIntosh et al., 1990

3. Hoffman et al., 1988a, Hoffman et al., 1988b; Van Rie et al., 1989; Van Rie et al., 1990; Wolfersberger et al., 1986 ; English and Slatin, 1992

4. Wolfersberger et al., 1986; Hofmann et al., 1988a; Hofmann et al., 1988b; Van Rie et al., 1989; Van Rie et al., 1990

5. Cantwell et al., 1972; Krieg and Langenbruch, 1981; Flexner et al., 1986; EPA, 1988; Vinson, 1989; and Melin and Cozzi, 1990

6. US EPA. Bt Plant-Pesticides Biopesticides Registration Action Document. http://www.agbios.com/docroot/articles/2000264-A.pdf

7. US EPA. Bt Plant-Incorporated Protectants October 15, 2001 Biopesticides Registration Action Document. http://www.epa.gov/pesticides/biopesticides/pips/bt_brad2/1-overview.pdf