permaculture

["Lawrence F. London, Jr." <lfl@intrex.net>]

-------- Original Message --------
Subject: [SANET-MG] Mystery of Disappearing Honeybees
Date: Thu, 26 Apr 2007 14:19:19 -0400
From: jcummins <jcummins@UWO.CA>
To: SANET-MG@LISTS.IFAS.UFL.EDU

ISIS Press Release 26/04/07
Mystery of Disappearing Honeybees
For some time now, honeybees have been disappearing from farmers’ hives
without a trace. Dr. Mae-Wan Ho and Prof. Joe Cummins on the trail of
possible culprits …


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Honeybees vanishing worldwide
The first alarm was sounded in autumn 2006. Honeybees are disappearing
across the United States, with half of the States affected and beekeeper
losing 30 to 90 percent of colonies; one beekeeper with 1 200 colonies
expected 9 to survive the winter [1]. The problem began more than two
years ago and has intensified in recent months [1-5]. The bees simply
vanish relatively suddenly, with little or no dead adults in or near the
colonies, leaving behind the queen and a few young. In cases where the
colony appears to be actively collapsing the workforce seems to be made
up of young adult bees, insufficient to feed the brood, but are
reluctant to consume provided feed [5]. This “colony collapse disorder”
(CCD) is particularly devastating for growers of fruits and vegetables,
as they depend on insect pollinators.

Since then, CCD has been reported from Germany, Switzerland, Spain,
Portugal, Italy, Greece, and the UK [6], where one of the biggest
beekeepers lost 23 of his 40 hives. But the Department of the
Environment, Food and Rural Affairs (DEFRA) said that “there is
absolutely no evidence” of CCD in the UK.

CCD has baffled scientists, because no one knows what causes it [5], and
ongoing efforts are being made to identify possible pathogens in the
bees and chemical residues in pollen, honey and bees. Viruses, fungal
diseases, parasitic mites, pesticides, or chemical designed to control
mites have considered by the authorities [7], as have GM crops [8-9],
and mobile phones [10] (Mobile Phones and Vanishing Bees, this series).
So how good is the evidence for the different suspects?

Extent and causes of decline both unknown
The United States National Research Council Committee on the Status of
Pollinators in North America published its report [7] in October 2006.
But the report was rather thin on data and information as to the precise
extent of the decline in honeybees or its causes.

The report discussed introduced parasitic mites, and the bacterial
pathogen that causes foul brood disease in detail, as there is extensive
scientific literature. But it barely touched on pesticides or GM crops,
and did not mention mobile phones at all.

Mites infestations
The introduced parasitic mites, Varroa destructor and Acarapis woodi,
began to cause infestation since the late 1980s, and mite infestation
became established in the US within a decade. Varroa destructor, an
external parasite of the honeybee, has caused dramatic declines in
honeybees in North America and throughout the world. During the winter
of 1995-1996, northern US beekeepers experienced their largest losses in
history; some states lost 30 to 80 percent of their colonies. These
losses have occurred despite heavy used of pesticides to control mite
populations. Pesticide resistance has become widespread and many
beekeepers are no longer able to use the few registered pesticides for
controlling Varroa.

The tracheal mite Acarapis woodi is an internal parasite of the
honeybee. It was first detected in the US in 1984, and initially caused
serious damage to colonies, but there appears to be heritable resistance
to the mite.

Parasitic mites cannot explain colony collapse disorder as there is no
evidence that mite infestation is directly involved, although it may
contribute indirectly by reducing the immunity of the bees to infections
by viruses, bacteria and fungi (see below).

Foul brood disease
Paenibacillus larvae is the most serious pathogen of honeybees. It
causes American Foul Brood disease (AFB), a disease of the honeybee
larvae. It is highly virulent and easily spread among colonies, and
generally fatal if untreated. During the first half of the last century,
AFB was the most serious threat to beekeeping, and caused tremendous
loss of colonies. The incidence of AFB was reduced dramatically by the
introduction of antibiotics, and by state inspection programme that
required the burning of infected hives. However AFB spores are
refractory to antibiotics and can persist on contaminated equipment for
more than 80 years. Treatment of colonies with active cases of AFB
eliminates disease symptoms, but withdrawal of antibiotics is generally
followed by disease recurrence. Resistance to antibiotics has also
become widespread since 1994.

As in the case of parasitic mites, foul brood disease is not associated
with colony collapse disorder.

Pesticides
The use of pesticides, especially insecticides on crops, is known to
kill or weaken thousands of honeybee colonies in the US each year, and
local bee kills have occurred sporadically for decades. However, the NAS
report considered it unlikely that this has “contributed significantly”
to the recent decline. The report stated [7, p. 79]: “Most
pesticide-caused honey bee kills are the result of accidents, careless
application, or failure to adhere to label recommendations and
warnings.” It has obviously ignored sub-lethal effects, particularly of
new pesticides that may turn out to be one of the most significant
single factors contributing to the current honeybee decline (see later).

Parasites reduce bee immunity
Varroa mites infestation reduces the immune response of the bees,
causing them to be prone to infection with virus, bacteria or fungi [11,
12]. A number of viral diseases are enhanced in the parasite-infested
bee colony, particularly the deformed wing virus disease that causes
crippling deformity in the bees [13]. Multiple viruses frequently infect
bees attacked by Varroa parasite. These viruses are spread not only by
the parasite, but also vertically from queen to brood [14, 15]. The
parasite-infested colonies are frequently treated with a pyrethroid
insecticide, fluvalinate, but the parasite has grown resistant to the
insecticide [16], and the insecticide may adversely influence the
behaviour of the honeybee (see below). Honeybees have 17 gene families
involved in immunity [17], roughly one-third the number of immunity
genes in Drosophila and Anopheles mosquitoes. Honeybees seem to have
limited immune flexibility, which may make them more sensitive to
devastating pathogens.

Pesticides disrupts bee behaviour at sublethal levels
Numerous pesticides have been found to disrupt bee behaviour following
sub-lethal exposures [18]. A wide array of pesticides including
fluvalinate (the chemical used to treat hives to eliminate parasites)
disrupted the behaviour of honeybees leading to feeding and navigation
problems [19]. Bees suffering from sub-lethal pesticide intoxication
resembled the behaviour of bees described by observers of the colony
collapse disorder. Sub-lethal doses of fipronil (a veterinary
insecticide) impaired the olfactory memory process of honeybees [20].
Spinosad, a prominent and much used natural insecticide fed to bumble
bees in pollen slowed down their foraging behaviour while a higher dose
of the insecticide caused colony death within two to four weeks [21].
See Requiem for the Honeybee [22] for more evidence that sub-lethal
effects of pesticides may be the single most important factor
contributing to disappearing honeybees.

Genetically modified (GM) crops may have sub-lethal effects on bees
The possibility that GM crops in North America is contributing to the
decline in honeybees was given little consideration by the NRC Committee
[7] even though the timing of the honeybee decline appears to coincide
with the widespread deployment of GM crops. GM crops are engineered to
tolerate herbicides, especially gyphosate, or to contain biopesticides
(the Bt Cry toxins from Bacillus thuringiensis), or both. The
biopesticide toxins produced in Bt crops are not highly or acutely toxic
to bees, but are toxic to butterflies, moths and beetles. Nevertheless,
in some instances, the toxins can kill bees or modify their behaviour.

The Bt toxin Cry1Ab caused reduced foraging activity in bees after they
were fed with syrup containing the toxin. However, the Bt toxin produced
less pronounced impacts on bee behaviour than the chemical pesticides
deltamethrin or imidacloprid [23]. Bt bacteria caused mortality in bees
when fed in broth cultures or sugar solutions [24]. A number of purified
Bt Cry toxins have been studied in the laboratory to determine their
toxicity to honey bees and bumble bees. For the most part, those studies
showed little threat from the Cry toxins. But sub-lethal effects on the
bees were not recorded in those experiments [25].

In a series of experiments in Jena, Germany, bees were found not to be
affected when fed on a diet of pollen doped with 100 times the
concentration of toxin found in the Bt maize pollen; and feeding trials
on larvae also showed no effects. In the field, bee colonies in flight
tents were fed with Bt maize pollen to which a 10-fold concentration of
Bt toxin had been added. Again, no negative effects were detected. But a
chance infestation by the parasite microsporidia resulted in
significantly more damage to the Bt-fed colonies compared with controls
[26]. Another limitation of the experiments so far is that they were
carried out with toxins derived from bacteria, not transgenic toxin
derived from the Bt crops, which are known to have very different
properties, as we have pointed out repeatedly, most recently in GM Maize
59122 Not Safe [27] (SiS 34).

Transgenic glyphosate-tolerant canola pollen was reported to pose no
threat to honeybees [28]. However, when organic, conventional, and
herbicide-tolerant canola were compared with regard to pollination by
wild bees in Alberta, Canada, the herbicide tolerant canola plots had
the greatest pollination deficit, while conventional and organic plots
were equally well served by the wild bees [29].

Clearly, the existing evidence calls for much fuller investigations on
the sub-lethal impacts of GM crops on bees, such as learning and feeding
behaviour, and immunity to disease. The potential consequences of
pollinator decline on food crops can be staggering, and the impact on
biodiversity may be irreversible [30].

Mobile phones and bee decline
There has been widespread report in the mainstream media that mobile
phones may be responsible for the decline of honeybees [for example, 6,
31]. The results are indeed startling. For details see Mobile Phones and
Vanishing Bees [10], and should be considered in the context of the
increasingly clear evidence that weak radiation from mobile phones and
base stations do have harmful effects on the health of human beings and
wildlife [32] (Drowning in the Sea of Microwaves, SiS 34).

The mystery remains
The mystery of disappearing honeybees is far from solved. The greatest
suspects so far are pesticides and radiation from mobile phone base
stations. However, it is likely that sub-lethal effects due to GM crops,
mites infestations and other factors which alter the bees’ behaviour,
affect their memory and learning process or compromise their health and
immunity will all have a role to play.

Honeybees may be our most sensitive indicator species for all the
environmental pollution and dangerous technologies we perpetrate. When
honeybees disappear, we too, shall follow shortly.



Mystery of d