The Truth About Honey Bees and Neonicotinoids.
How these systemic pesticides are decimating honey bee populations.
There are two types of adult honey bees; summer bees and winter bees. Summer bees have a short life span of only 40 days, their role is to gather food and feed the larvae. These larvae will eventually become the winter bees, who thrive from September throughNovember and who enjoy a six month lifespan. These bees are responsible for colony overwintering.
However, large numbers of overwintering bees are dying in the U.S., with beekeepers experiencing losses of 30% in managed honey bee colonies each year, over the last five years (van Engelsdorp et al. 2012). These bees are suffering due to pathogens, pests, poor nutrition and pesticides. Summer and winter bees are physiologically different from one another. The winter bees longer lifespan means they experience more frequent exposure to pesticides and pathogens. They are often more sensitive to pesticides than summer bees, possibly due to their greater fat deposits, which allow pesticides to accumulate. Added to that, colder temperatures make pesticides more toxic to bees (Decourtye et al. 2003; Johansen 1975; Belzunces et al. 2001b).
How Neonicotinoid Insecticides Threaten Bee Populations.
Analysis of overwintering honey bee hives has brought to light a high level of contamination from pesticides (Mullin et al. 2010). While these are killing bees from inside the hive, bees are also dying while foraging in fields (Krupke et al. 2012). A big part of the problem is systemic insecticides called neonicotinoids, which are always present in the plant. This means that the mitigation strategies sometimes applied to minimize the negative impact on bees are not successful. Around 45% of U.S. crops have been treated with systemics, a number that continues to rise (Mullin et al. 2010; Stokstad 2012; Spivak et al. 2011).
There are two ways that pesticides can affect bee populations: by killing them directly, and by causing sub-lethal effects such as impaired memory, learning and foraging, which can lead to nutritional deficiencies. Pesticides can also weaken bee immune systems, affect brood development and decrease lifespans (Henry et al. 2012; Pettis et al. 2012; Wu et al. 2012; Desneux et al. 2007).
Today's Bees Are Exposed to More Pesticides Than Ever Before.
Bee exposure to pesticides is widespread. Hives can be treated with pesticides to kill mites and bees can come also into contact with pesticides while foraging, bringing contaminated pollen and nectar back to the hive. A study by Mullin et al. (2010) discovered 121 different pesticides and metabolites present in 887 wax, bee and pollen samples. This averaged at about six pesticides in each sample. It is important to understand this as a negative factor on honey bees, pesticide mixtures have been shown to be more toxic to bees than individual products (Johansen 1977; Atkins 1992; USHR 2008; Pilling and Jepson 1993; *** et al. 2003; Isawa et al. 2004).
How Sub-lethal Doses of Pesticides Affect Bee Larvae.
Larvae are fed pollen by nurse bees that has been collected by forager bees. A study by Krupke et al. (2012) found concentrations of clothianidin and thiamethoxam in pollen used in sick hives. These sub-lethal doses can cause delayed development of adult bees, which can in turn make bees more susceptible to mites. Pesticides in the brood comb can also shorten lifespans of adult bees (Wu et al. 2011).
A study by Lu et al. (2012) ascertained that feeding neonicotinoids to bees can kill entire colonies at sub-lethal concentrations of 20 ppb. This is a similar dose to that found in the field.
How Neonicotinoids Impair Bee's Internal Navigation Ability
In a study by Henry et al (2012), equal numbers of treated and untreated bees were release 0.6km away from the hive. Some were released in familiar surroundings and others were released in unfamiliar surroundings. From the group of treated bees released in familiar surroundings, 10% of them didn't find their way back to the hive. Even more unfortunate, 32% of treated bees released in unfamiliar surroundings didn't make it back.
As most commercial honey bee hives are moved from place to place and released in unfamiliar environments, it makes the results of this study especially important. Constant movement increases the rate at which hives are decimated when bees are unable to navigate their surroundings.
Honey bees are being subjected to increased levels of pesticides, which is having a devastating on their populations. Widespread use of neonicontinoids play a large role in this problem, but the mixture of pesticides that bees are subjected to are also to blame. Pesticides can negatively impact bees' immune systems, interfere with brood development and are a catalyst for poor nutrition caused by impaired foraging and tainted food supplies. The sub-lethal doses of pesticides found in hives are affecting bee health and behavior like never before, leading to shortened life spans, increased vulnerability to pathogens and in many cases, complete colony collapse. Given that pollinators such as bees, birds and bats affect up to thirty five percent of the earth's production of crops and are directly responsible for the increased output of eighty seven of the world's leading crops, it should be self evident that what is bad for bees is bad for everyone.
*Image courtesy of Dollar Photo Club
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