One third of global food production relies on pollinators to some degree, while 80% of flowering crops are pollinated by honey bees and other insects, according to the US Honey Bee Health Coalition. The current challenge, says the coalition, is that 28-33% of the US honey bee population is now lost each winter, compared with a historical level of 10-15%. The causes of these increased losses are said to include lack of genetic diversity in bees, due to modern management and selective breeding practices; lack of a varied diet and malnutrition, due to declining wild spaces and increased monocultures; pests and diseases, including increased susceptibility to Varroa mites, due to intensification of commercial beekeeping and miticide resistance; and incidental pesticide exposure, due to intensified agriculture and beekeeping.
Pesticides can find their way into hives through pollen, which contains on average nine different pesticides – and sometimes as many as 21 pesticides, according to the US Pollinator Stewardship Council. At the 1st US Agchem Summit in Washington DC in December 2015, the Council’s Michelle Colopy highlighted research by Penn State University entomologist Chris Mullin that showed almost 60% of 259 wax and 350 pollen samples tested contained at least one systemic pesticide and 47% contained the fungicide chlorothalonil. Also, almost all comb and foundation wax samples were contaminated with an average of six pesticide detections per sample and a high of 39 (PLoS One, doi: 10.1371/journal.pone.0009754).
’We need to understand the total chemical burden on pollinators, whether deliberately introduced into hives or brought back from the environment,’ Mullin said. ‘Although 70% of 230-240 pesticides are found in hives, no individual pesticide correlates with bee decline, therefore there is a need to look at ingredients other than the active ingredients.’
Research at his university has found the formulated fungicide chlorothalonil is more toxic than the active ingredient alone, resulting in six times more bee deaths, while formulated amitraz was four times more toxic than the active alone. Other formulations, particularly fungicides, can be up to 26,000 times more toxic than the active ingredients. Other research, meanwhile, had shown that pesticide spray tank adjuvants, like organosilicons, interfere with the learning abilities of honey bees, Mullin pointed out. ‘Higher surfactancy would appear to increase toxicity. There seems to be a synergistic impact when more than adjuvant is used,’ he said. ‘We need to share information regarding toxicity in formulations.’
While neonics are not banned in the US, some concern was expressed by Reed Johnson, from Ohio State University, about their use for corn seed treatments, and the possible impact on pollinators from drifting dust from the seeds as they are planted. Bee forage ranges can be up to 10km in diameter, thereby increasing their exposure potential, and statistically one treated seed could kill a whole colony. ‘Despite this, bees still exist,’ he added, noting, however, that it is ‘now rare to see massive colony deaths’. Seed treatments are over-used and integrated protection should be encouraged, he said.
Ron Biever, a consultant with Smithers Viscient, emphasised the unreliability of research into pesticide impact, due to four main causes: poor study design; inadequate lab protocols; data analysis and reporting problems; and improper use of biological reagents and reference materials. The result, said Biever, is that ‘consumers don’t know who to believe and trust – government, NGOs, academia or industry’.
Ann Bartuska, deputy undersecretary for research, education and economics at the US Department of Agriculture, went further, saying that ‘publications do not want to accept [research] papers with ‘null’ results’.
The US regulatory process includes the conduct of studies at varying levels of environmental control, ranging from Tier 1: highly controlled laboratory studies, involving acute bee toxicity and larval dietary test; through semi-controlled Tier 2 semi-field studies, including pollen and nectar residue studies involving a number of crops, as well as bee colony feeding studies; to non-controlled ‘real world’ Tier 3 field studies. While Biever admitted that laboratory studies have concluded that sub-lethal dietary doses of neonics are capable of harming individual bees, he also emphasised that when examining ‘eusocial’ insects, such as bees, it is important to establish whether the effects translate into effects on the whole colony in the field.
US government action
Bartuska outlined the US government’s strategy, based on President Obama’s memorandum of June 2014, aimed at improving pollinator health by the reduction of bee colony losses during winter by more than 15% within 10 years; an increase in the eastern population of Monarch butterflies to 220m by 2020; and the restoration or enhancement of 7m acres of land for pollinators by 2020.
The American Honey Producers Association believes farmers should be able to protect their crops against pests, just as beekeepers must protect bees from harm caused by pesticides. ‘We believe in the judicious use of crop protection products.’
And as Bartuska pointed out: ‘Pesticides will continue to be part of the toolbox but how do we persuade farmers to get involved in an integrated pest management approach that continually improves and reduces risks to pollinators?’
In a final twist on the pollinator and pesticide story, factory-farmed bumble bees could be used to deliver a biological fungicide to crops, such as strawberries, rapeseed and apples, and even antibiotics to trees, according to Canadian start-up company, Bee Vectoring Technology. The company has been researching the concept for 20 years, and has developed Vectorite, a mixture of products that allow the active ingredient to become attached to the bee’s hairy legs and body as it walks through a special tray as it leaves the hive. It is possible to include one or several actives mixed together to control a range of pests. The company says it has conducted eight years of successful field trials, and has seen increased crop yields coupled with greater pesticide effectiveness.
New US research project
German agchem major Bayer and Project Apis m, a non-profit organisation dedicated to pollination research, are sponsoring a five-year $1m research initiative, developed out of Bayer’s Healthy Hives 2020 initiative launched in 2015, to improve the health of US bee colonies. Project Apis m will oversee the administration of Bayer-funded research grants with a number of objectives including an economic assessment of the ‘true’ cost of commercial beekeeping operations; the creation of a set of Best Management Practices based on definitive colony health performance data; an evaluation of ‘smart hive’ technology to monitor colony health during commercial migratory operations; and an assessment of honey bee genetic traits relevant to colony resistance to pests and diseases as well as pollination efficiency and honey production in the US.
UK farmers – bee aware
The debate over the two-year Europe-wide ban of neonicotinoid seed treatments clothianidin, thiamethoxam and imidacloprid rages on. The ban, which began on 1 December 2013, was brought in because the chemicals were considered a risk to wild bees and the honey bee – pollinators of a variety of crops and plants, worth some £510m to the UK agriculture and horticulture sector. But many UK scientists and farmers believe the scientific evidence surrounding the decision is ambiguous.
Guy Smith, an arable farmer in Essex, and vice president of the National Farmers’ Union (NFU), addressing the question, Are farmers ‘bee’ aware?, at SCI HQ in London in March 2016, said: ‘We felt that the EU ban was done on a rather populist platform rather than on any sound scientific evidence, and we are increasingly worried about the way pesticides are regulated in the EU. Farmers in Britain are being placed at a disadvantage with greater levels of regulation than their competitors in different parts of the world.’
As a result of the ban, many famers growing oil seed rape (OSR) have witnessed considerable damage to their crops, and according to the NFU, the planting of oilseed rape was 10-20% down in 2014. In response, in 2015, NFU applied for, and received, a derogation to use the insecticides in counties where the damage was most pronounced, ie in 5% of OSR crops.
OSR is a small seed, sown late August to early September when the ground is dry, making it very difficult to establish. It is prone to attack from slugs, which are controlled by metaldehyde; and cabbage stem flea beetles, which are controlled by neonicotinoids. ‘Farmers use neonicotinoid seed treatments as an insurance. Experience suggests that one in three years they will lose the crop if it is not protected from the flea beetle,’ explained Smith. ‘It is very difficult to grow OSR without chemical control.’
Once the plant is growing, the beetles may still pose a problem – the neonicotinoid seed treatment is not foolproof, and the beetles remain active, laying their eggs in the stem of the plants. Farmers may then use pyrethroids to control the pest; however, with growing pyrethroid resistance, they are increasingly looking to a combination of insecticides to ensure a healthy crop.
By late April, the oil seed plant is in full flower, producing pollen and attracting bee activity – though oilseed rape does not need bees for pollination, as it is wind-pollinated. Farmers may spray selective insecticides, but according to Smith: ‘The majority of British farmers are bee aware, and will only spray their crops in the evening when the bees have returned to their hives – this is standard practice for flowering crops in the UK today.’ Currently, the NFU is developing a notification strategy: through social media, farmers can alert bee keepers when they intend to spray their crops with a particular product.
There are also several environmental schemes in UK where farmers are paid to treat part of their farm as a conservation zones away from the production zone. Smith, for example, has an area of marshland on which he plants pollen-rich nectars or plants that are good for wild birds, and also provide habitat for ground nesting birds. ‘I believe in using intensive conservation on the 5% margin and intensive production on 95% on my land – to achieve a good balance between biodiversity and crop production,’ he said.
Nevertheless, colony collapse disorder (CCD) in honey bee populations is a problem. And the number of wild bee species have declined in the UK over the past few decades. Research increasingly points to several contributing factors, including climate change, intensive farming and loss of habitat, the Varroa mite – a particular parasite of the honey bee – and pesticides, though as yet there is no frontrunner. The only place in the world where they have not seen significant CCD is Australia, pointed out Smith – where they use neonicotinoids and do not have the Varroa mite. ‘But the Australians have very strict phytosanitary control at their borders,’ he added.
‘Simply banning a class of insecticide is not going to deal with the problem,’ said Julian Little from Bayer CropScience, adding: ‘The fact that Australia has the healthiest bees on the planet despite using large amounts of neonicotinoids is the clearest indicator yet that not having Varroa is the biggest thing that we can do for bees. Likewise the partial bans on neonicotinoids in France for nigh on 10 years has had zero impact on bee health – there, Varroa is rampant.’
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