# How do genetically modified crops affect honey bees?

This question is brought up in the CCD discussion enough to take a closer look at just how much do genetically modified crops/plants impact honey bees.

Many plants/crops today are modified to include pesticides within the plant itself.  First of all, do the toxins now produced by the plants get distributed into the pollen loads the bees pick up?

According to a study in 1999 by the Scottish Crop Research Institute, Invergowrie, Dundee, DD2 5DA, ROYAUME-UNI:

“The presence of GM pollen in largely non-GM Brassica pollen loads, and the generation of mixed GM and non-GM progeny following the pollination of male sterile plants with pollen from single bees, demonstrates directly that bees can readily spread OSR pollen around their foraging area.”

So, as of 1999, there is suggestion that bees can indeed carry toxin loaded pollen from genetically modified plants to the hives.  The next question then is, Is the pollen really toxin loaded?

Field Deposition of Bt Transgenic Corn Pollen: Lethal Effects on the Monarch Butterfly, by Laura C. Hansen Jesse and John J. Obrycki © 2000

Which is summarized here…

We present the first evidence that transgenic Bacillus thuringiensis (Bt) corn pollen naturally deposited on Asclepias syriaca; common milkweed, in a corn field causes significant mortality of Danaus plexippus L. (Lepidoptera: Danaidae) larvae. Larvae feeding for 48 h on A. syriaca plants naturally dusted with pollen from Bt corn plants suffered significantly higher rates of mortality at 48 h (20±3%) compared to larvae feeding on leaves with no pollen (3±3%), or feeding on leaves with non-Bt pollen (0%). Mortality at 120 h of D. plexippus larvae exposed to 135 pollen $\text{grains}/\text{cm}^{2}$ of transgenic pollen for 48 h ranged from 37 to 70%. We found no sub-lethal effects on D. plexippus adults reared from larvae that survived a 48-h exposure to three concentrations of Bt pollen. Based on our quantification of the wind dispersal of this pollen beyond the edges of agricultural fields, we predict that the effects of transgenic pollen on D. plexippus may be observed at least 10 m from transgenic field borders. However, the highest larval mortality will likely occur on A. syriaca plants in corn fields or within 3 m of the edge of a transgenic corn field. We conclude that the ecological effects of transgenic insecticidal crops need to be evaluated more fully before they are planted over extensive areas.

So we can see there is some suspected evidence that toxicity is transmitted into the pollen of the plants and that pollen is not limited to just the plants it is derived of, but in fact that pollen can be transported by wind or insects to other plants in which that same toxin loaded pollen can be further spread by pollinating insects to their nests.

The next question raised then is ” is the transmitted toxin lethal to honeybees as it seems to be to other insects?”

We find one answer in the 2007 article :

“A Meta-Analysis of Effects of Bt Crops on Honey Bees (Hymenoptera: Apidae)”

Jian J. Duan,1 Michelle Marvier,2* Joseph Huesing,1 Galen Dively,3 and Zachary Y. Huang4
Background
Honey bees (Apis mellifera L.) are the most important pollinators of many agricultural crops worldwide and are a key test species used in the tiered safety assessment of genetically engineered insect-resistant crops. There is concern that widespread planting of these transgenic crops could harm honey bee populations.
Methodology/Principal Findings
We conducted a meta-analysis of 25 studies that independently assessed potential effects of Bt Cry proteins on honey bee survival (or mortality). Our results show that Bt Cry proteins used in genetically modified crops commercialized for control of lepidopteran and coleopteran pests do not negatively affect the survival of either honey bee larvae or adults in laboratory settings.
Conclusions/Significance
Although the additional stresses that honey bees face in the field could, in principle, modify their susceptibility to Cry proteins or lead to indirect effects, our findings support safety assessments that have not detected any direct negative effects of Bt crops for this vital insect pollinator.
According to this study, Bt does not have a lethal effect on honey bees or honey bee larvae at the time of the study but does indicate that it is possible for bees susceptibility to such to change.
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