Requiem for the Honeybee

includes the relationship between genetically engineered crops and 
Bayer's imidacloprid insecticides.

Neonicotinoid insecticides used both in sprays and seed dressing may 
be responsible for the collapse of honeybee colonies.
by Prof. Joe Cummins

eonicotinoid insecticides are harmful to the honeybee

There has been a great deal of concern over the decline of the 
honeybee across the US, Europe and Australia [1] (The Mystery of 
Disappearing Honeybees, this series). The United States National 
Research Council (USNRC) Committee of the Status of Pollinators in 
North America report [2] focused on the impact of parasites, fungi, 
bacteria and viruses, but did not pay much attention on the impact of 
pesticides and genetically modified (GM) crops, which may have lethal 
or sub-lethal effects on the bee's behaviour or resistance to 
infection. There have been strong responses to the report on that 
account. On the other hand, any suggestion that GM crops and 
pesticides may be causing the decline of honeybees is met with heated 
denial from the proponents.

Certainly, honeybees are declining both in areas where GM crops are 
widely grown, and in other areas where GM crops are released in small 
test plots. Is there a common thread that links both areas?  Yes 
there is, the universal use of systemic pesticide seed dressing in GM 
crops and conventional crops; in particular, the widespread 
application of a relatively new class of systemic insecticides - the 
neonicotinoids - that are highly toxic to insects including bees at 
very low concentrations. Systemic pesticide seed dressings protect 
the newly sprouted seed at a vulnerable time in the plant's 
development. Seed dressings include systemic insecticides and 
fungicides, which often act synergistically in controlling early 
seedling pests.

The neonicotinoid insecticides include imidacloprid, thiamethoxam, 
clothianidin, and several others. Imidacloprid is used extensively in 
seed dressing for field and horticultural crops, and particularly for 
maize, sunflower and rapeseed (canola). Imidacloprid was detected in 
soils, plant tissues and pollen using HPLC coupled to a mass 
spectrometer. The levels of the insecticide found in pollen suggested 
probable delirious effects on honeybees [3]. For several years since 
2000, French and Italian beekeepers have been noticing that 
imidacloprid is lethal to bees, and the insecticide is suspected to 
be causing the decline of hive populations by affecting the bee's 
orientation and ability to return to the hive.

Confused and disoriented bees

A team of scientist led by the National Institute of Beekeeping in 
Bologna, Italy, found that pollen obtained from seeds dressed with 
imidacloprid contains significant levels of the insesticide, and 
suggested that the polluted pollen was one of the main causes of 
honeybee colony collapse [4]. Analysis of maize and sunflower crops 
originating from seeds dressed with imidacloprid indicated that large 
amounts of the insecticide will be carried back to honey bee colonies 
[5]. Sub-lethal doses of imidacloprid in sucrose solution affected 
homing and foraging activity of honeybees. Bees fed with 500 or 1 000 
ppb (parts per billion) of the insecticide in sucrose solutions 
failed to return to the hive and disappeared altogether, while bees 
that had imbibed 100 ppb solutions were delayed for 24 h compared 
with controls [6]. Imidacloprid in sucrose solution fed to the bees 
in the laboratory impaired their communication for a few hours [7]. 
Sub-lethal doses of imidacloprid in laboratory and field experiment 
decreased flight activity and olfactory discrimination, and olfactory 
learning performance was impaired [8].

Bayer corporation scientists reported that neither honeybees exposed 
to imidacloprid in sunflower seeds dressed with the insecticide [9] 
nor maize seeds dressed with the insecticide or released from the 
seeds during planting [10] were detrimental to honeybees. The Bayer 
studies did not deal with sub-lethal behaviour of intoxicated bees. 
An independent study found that imidacloprid was released to the 
environment from treated maize seeds during seed planting [11]. Bayer 
eco-toxicologists directed harsh criticisms at reports showing lethal 
or sub-lethal toxic effects of imidicloprid seed dressing and 
concluded that imidacloprid does not pose any significant risk to 
honeybees in the field [12], without, however, disproving the 
findings. It is simply yet another case of the anti-precaution 
principle being applied [13] (Use and Abuse of the Precautionary 
Principle, ISIS News 6)

Turning to GM crops such as maize, canola, cotton and soybean it is 
clear that all of these GM crops, with or without Bt genes, use seeds 
most of which are coated with neonicotinoid pesticides highly toxic 
to honey bees.  For example, Herculex maize with Bt genes to control 
rootworm, like Yieldgard corn borer resistant maize, is planted with 
seeds dressed with a neonicotinoid insecticide and a fungicide. 
Furthermore, the GM planting requires setting aside plots of non-GM 
maize making up 20 percent of the planted area as a "refuge" to 
discourage the evolution of resistant insects.  But the "refuge" is 
sprayed with neonicotinoid pesticide to protect its yield [14], and 
is more like a death camp for insects. Monsanto's US Patent 6,660,690 
provides for coating GM seeds with chemical pesticides [15].

Toxicology known

The toxicology of neonicotinoid insecticides is well known. The 
insecticides are inhibitors of acetycholine receptors (i.e., they are 
nerve poisons).  They have low toxicity for mammals, birds and fish, 
and are used to control fleas on dogs and cats [16]. The nicotinic 
acetylcholine receptor gene family of the honeybee has been studied; 
it has 11 subunit members, a larger number than the fruit fly or 
mosquito. The genes for the subunits employ alternatively spliced 
transcripts to increase receptor diversity, and the messenger RNAs 
are edited to replace specific A bases with I bases. Information on 
the receptor should allow for development of insecticides that are 
not harmful to bees [17].

In conclusion, the US NRC Committee did not deal with the heated 
debate over neonicotinoid pesticides and honeybee decline. Instead, 
that it seemed to suffer from tunnel vision and to be overcautious 
about matters that threaten large corporations.

We urgently need a thoroughly independent committee to consider the 
full range of factors that may be contributing to the decline of 
bees, including pesticides, GM crops and electronic devices, before 
the bees become extinct.