3 Pests and Pesticides


The danger of importing bumblebees for pollination
Neonicotinoids 29 April 2013
Honeybees entomb their food to protect against pesticides  April 2011
Genetic weapon for the fight against varroa mites December 2010


Asian Hornet

Potential threat to domestic Honeybees! Alien Invasive –  Spreading in France. Not yet present in GB, but it is considered likely to arrive soon.
The impact on honeybees can be slightly limited by reducing the hive entrance to a narrow slit but the hornet will pick off honeybees flying around the hive. The places it is most likely to be found are in southern parts of England. It may be able to cross the channel from France. It also could be accidentally imported amongst goods such as in the soil of pot plants, or cut flowers, fruit and timber.

Sightings should be reported, along with a photograph and details of where you saw it. Emailalert_nonnative@ceh.ac.uk
If possible, post a sample to the National Bee Unit for examination to confirm identity details at:

Do not under any circumstances disturb or provoke an active hornets nest.
This is a very defensive species, always ready to attack and sting in defence of its nest. And will chase intruders for long distances. Hornets can sting multiple times and do not die after stinging a human as is typical for a  worker honeybee, because a hornet’s sting is not barbed. They can also bite and sting at the same time.

They are difficult to confuse with any other insect. The hornet queens queens are up to 30 mm in length; workers up to 25 mm (slightly smaller than the native European hornet. This is the only hornet that has an entirely dark brown or black velvety body, bordered with a fine yellow band. There is only one band on the abdomen: 4th abdominal segment is almost entirely orangey/yellow. Legs brown with yellow ends and the head is black with an orangey/yellow face. As with other social wasps, the colonies last one season, and only the fertilised queens hibernate.

Habitat and threats:
This hornet is an invasive non-native species from Asia. It arrived in France in 2005 and has been is spreading rapidly.  It is thought to have arrived in a container from China. As a highly effective predator of insects, including honey bees and other beneficial species, it can cause significant losses to bee colonies, other native species and potentially ecosystems.
In France this hornet, so far, seems to only be attacking adult bees and not the brood. They nest in tall trees in urban and rural areas and nests are also found in garages, sheds, under decking and rarely, in holes in walls or in the ground.


Honeybees, wild species of bees and also insects pollinate many crops but certain crops can be pollinated more effectively and efficiently by bumblebees. Their use as pollinators was discovered in the 1980s. Nowadays between 40-50,000 commercially reared bumblebee colonies, each containing up to 100 worker bees are imported annually to the UK. Worldwide more than one million colonies are sold each year.

Some types of bumblebees have long tongues so they are well suited to pollinating crop flowers that other bees can’t reach into. The bumblebee also buzz pollinates by placing its upper body close to the anthers of a flower, vibrates its flight muscles and this vibration shakes the pollen from the anthers, enabling more efficient pollination.

Bumblebees are also very fast pollinators! Studies have demonstrated that 5 colonies of bumblebees produced yields equal to using 7.5 honey bee colonies per hectare, despite the significantly greater size of honey bee colonies. Bumblebees also work longer hours, not being affected by the cold as much as other bees. Typical bumblebee colonies may consist of as few as 40 workers, or reach around 120 workers. Honey bee colonies by contrast, are much larger, with 20,000 to 80,000 workers.

Soft fruit and vegetable growers are well aware of the efficiency and effectiveness of bumblebees for pollination. Some of the crops that they now use the bumblebees for are strawberries, cranberries, kiwi fruit and blueberries, peas and beans. Even where crops can be self pollinated (such as some tomatoes), nevertheless, they produce more and bigger fruits with the aid of bumblebees.

Imported bumblebees are essential; unfortunately, this trade is spreading diseases, with dire consequences for local populations of bees.

A study was published in the Journal of Applied Ecology. Researchers bought a small selection of colonies from three different suppliers in Europe. Some colonies were a subspecies native to the UK and others were non-native. All were meant to be disease-free but when they were tested 77% of the colonies were found to be carrying parasites. Parasites were also found in the pollen food supplied with the bees.
Testing revealed that the imported bumblebees carried a range of parasites – three main bumblebee parasites ‘Crithidia bombi, Nosema bombi and Apicystis bombi’, three honeybee parasites ‘Nosema apis, Ascosphaera apis and Paenibacillus larvae’, and two parasites which infect both bumblebees and honeybees ‘Nosema ceranae and deformed wing virus’.

The results suggest that current regulations and protocols governing bumblebee imports are not effective. Although the licences require colonies to be disease free, colonies arriving in the UK are not screened to ensure compliance and the regulations do not apply to imports of the native subspecies.
Stricter controls over bumblebee imports to the UK are urgently required to prevent diseases spreading to native bumblebees and honeybees, scientists have warned.
Producers need to improve disease screening and develop a parasite-free diet for their bees. Regulatory authorities need to strengthen measures to check bees on arrival in the UK and extending regulations to cover imported colonies of native subspecies. Unless this is done then potentially tens of thousands of parasite-carrying bumblebee colonies may be imported into the UK each year, and hundreds of thousands worldwide.

This is the first study of its kind in the UK but research in North America, South America and Japan suggests that parasites introduced by commercial bumblebees may be a major cause of population declines of several bumblebee species.

Many bee species already show significant population declines due to multiple factors. The introduction of more or new parasite infections will exacerbate this and could quite possibly further drive declines.


29 April 2013  The European Commission acknowledged that pesticides have been identified as one of several factors which may be responsible for the decline in number of bees and has put a two year restriction on the use of three neonicotinoid pesticides – clothianidin, imidacloprid and thiametoxam.
This will come into force on 1st December 2013 and will be reviewed after two years. Fifteen countries voted in favour of a ban. The UK did not support it, arguing that the science behind the proposal is inconclusive. Nearly three million signatures were collected in support of a ban and protesters against these pesticides recently rallied in Westminster. Eight countries voted against, while four abstained. Some restrictions are already in place for these pesticides in France, Germany, Italy and Slovenia.

These three neonicotinoid products are used in seed treatment, soil application and foliar treatment on plants that are attractive to bees. It will not apply to crops non-attractive to bees, or to winter cereals. There will also be a ban on the sale of neonicotinoids to amateur growers. The remaining authorised uses are available only to professionals, with exceptions limited to possible treatment of bee-attractive crops in greenhouses and open-air fields only after flowering.

Neonicotinoids are nicotine-like chemicals which act on the nervous systems of insects. They have been in use for more than a decade and represented an improvement on earlier pesticide sprays particularly because they were thought to be a lower threat to humans and other mammals than many older sprays. They are now the world’s most widely used group of pesticides. They are used prophylactically instead of reactively which is rather like us taking antibiotics throughout the year just in case we are exposed to someone with a chest infection in December.
Imidacloprid is possibly the most widely used. It is applied to the soil and taken up by the whole plant. It is systemic, meaning it turns the plant itself into a poison factory, with toxins coming from roots, leaves, stems and pollen to provide protection from insect pests as the plant grows. It is also used for coating seeds before planting to stop insects in the soil attacking them. It is used on timber, animal pests and as a foliar treatment for crops including: cereals, cotton, grain, legumes, potatoes, apples, pears, rice, turf and vegetables.

The scientific basis for the ban was a report published by the European Food Safety Agency (EFSA) which concluded that the three products pose a high risk to honey bees in crops producing nectar and pollen.

Other scientific studies
One study suggested that neonicotinoids affected the abilities of colonies of bees to produce queens. More recent research indicated that the pesticides damaged bee brains.
The American Bird Conservancy In March 2013, published a review of 200 studies on neonicotinoids including industry research obtained through the US Freedom of Information Act, calling for a ban on neonicotinoid use as seed treatments because of their toxicity to birds, aquatic invertebrates, other wildlife and (indirectly) bats, amphibians and insect eating birds.
Another study conducted on rats suggests that these pesticides may adversely affect human health, especially the developing brain.
A study by the Sussex University has claimed the water soluble pesticides accumulate in the soil and water, potentially damaging a wider range of wildlife and the soil itself. Prof Dave Goulson, who led the study, said harm to bees may be just the tip of the iceberg as 90 per cent of neonicotinoids go into the soil and leach into groundwater, where they persist for years resulting in a sustained exposure to these pesticides. They can be absorbed by hedgerows and plants that wildlife relies on. Mice and other mammals eat the seeds, while butterflies and moths survive on nectar and pollen from plants absorbing the chemicals. This is likely to have effects far beyond the pest insects they intend to target. For example, less than one part per billion of imidacloprid in streams is enough to kill mayflies. The study also highlights risks for grain-eating birds such as partridge, which need eat only a few neonicotinoid-treated grains of crop to receive a lethal dose.

Chemical companies and pesticide manufacturers and even the UK Government argue that the science is inconclusive, and that a ban would harm food production. They argue that food production could slump. But there is little evidence of this from countries like France and Italy which already have partial bans. Chemical companies also warn of a return to older pesticides that are even more harmful to bees, but again there is little evidence for this and recent farming trends are towards using natural predators and crop rotation to control any pests.

The Commision’s restriction marks another milestone towards ensuring a healthier future for our honeybee, bumble bees and solitary bees. About 80 % of all pollination is due to the activity of bees. Without bees, there would be little food, as everything from corn and tomatoes to apples and almonds grow from flowers that need pollinating. Declining populations of pollinators have been identified as a serious risk to global food production.

Comments from the public
If we wait until it’s proved one way or the other it could be too late for the bee population. There are people who hire out bee hives to apple growers in a kind of pollinators business because there aren’t enough bees around to do the job. Better to exclude these chemicals now and look at the results in a couple of years, than do nothing and find we’ve lost bees altogether.
The onus should be on the manufacturers to prove there isn’t an effect before they release these chemicals for sale/use. And massive fines if they get it wrong! It shouldn’t be up to others (including, indirectly, the taxpayer) to prove there *is*. Who pays when all the bees die? Not the manufacturers, they’ve banked all their profits. We pay with a degraded environment and rocketing food costs! 
Without bee pollination many UK grown crops would fail. Loss of bees would be far more expensive than banning these pesticides until we know they are responsible.


The pollen entombing phenomenon was first noted in an obscure scientific paper in 2009. Since then further research, conducted by Jeff Pettis, an entomologist with the US Department of Agriculture, has been finding the behaviour more frequent.

Honeybees appear to be taking emergency measures to protect their hives from pesticides by sealing up cells full of contaminated pollen to put them out of use, and protect the rest of the hive from their contents. Pollen is the protein food used to feed growing young bees.
The bees that entomb cells of pollen are the housekeepers, different from the bees that go out to collect pollen from plants (foragers). It seems that foragers cannot detect high levels of pesticides but that the pollen underwent subtle changes when stored. These changes a lack of microbial activity compared with pollen that has fewer pesticide residues seemed to be involved in triggering the entombing effect. Bees would not normally seal off pollen. Entombed pollen is identified as having sunken, wax-covered cells amids’t normal, uncapped cells. The implication is that the bees are recognising that something is wrong with the pollen and encapsulating it. This is an extraordinary example of the natural world adapting swiftly to our depredations.

Pollen stored in the sealed-up cells has been found to contain dramatically higher levels of pesticides and other potentially harmful chemicals than the pollen stored in neighbouring cells. Bees are also sealing off pollen that contains substances used by beekeepers to control pests such as the varroa mite and these substances may also be harmful to bees. It’s a balancing act if the parasite is not controlled then bees die. If you control the parasite, bees will live but there are side-effects.

But the bees last-ditch efforts to save themselves appear to be unsuccessful. Entombing behaviour is found in many hives that subsequently die off. The presence of entombing is the biggest single predictor of colony loss. It’s a defence mechanism that has failed. These colonies were likely to already be in trouble, and their death could be attributed to a mix of factors in addition to pesticides.

There could be many reasons for the bees dying. Entombing is yet another indication that a combination of stress factors is contributing to the plight of our bees.
Other factors are bee pests, genetic inbreeding, pollution, substitute feeding, globalisation spreading bee diseases around the world, unseasonable weather and mono agriculture. The latter reduces bee habitat and replaces multiple food sources with single, less nutritious, sources. Bees in areas of intensive agriculture were suffering from poor nutrition compared with bees with a diverse diet. Pesticides are not likely to be the biggest single cause of bee deaths but they don’t help.

The decline of bee populations has become an increasing concern in recent years. Colony Collapse Disorder is the name given to the unexplained death of bee colonies. This is affecting hives around the world.


Scientists have developed a genetic technique which could be used in the fight against the honeybees worst enemy – the parasitic varroa mite (varroa destructor). This technique is at an early, experimental stage but could be developed over the next few years into a medicine which can target the mites in the hive without damaging the bees. The technique would fool the immune system of the mite into attacking itself and therefore self destruct. The treatment would not affect any other pollinating insects.

These mites are considered the biggest global killer of honeybees contributing to the decline of these important pollinating insects. They were first found in the Southeast Asia in the early 1900’s and have now spread worldwide.

Female mites lay eggs on honeybee larvae which, when developed into adult bees, will have misshapen wings or none at all. Because these bees are unable to fly they will not be able to forage for the colony. If there are severe infestations of varroa there will be too many damaged bees and the colony would die out.

Over the past ten years or so many mites have developed resistance to some of the chemical treatments that beekeepers use to try to control the spread of this parasite.
Beekeepers also use other ways to control these mites e.g. essential oils, trapping or dusting the bees with icing sugar (because mites do not like this desiccant and also the bees groom each other, the mites drop off).

Unfortunately these methods are not quite so effective so this promised new medicine would be a massive help in slowing the decline of honeybees.

Mites on bee                    Deformed wings

Licence for photographs  http://www.nationalarchives.gov.uk/doc/open-government-licence/