Around this time last year in Germany a catastrophic error was being made during the treating of maize seed with the insecticide clothianidin.

A failure to use the glue that sticks the pesticide to the seed led to the chemical getting into the air during drilling, and resulted in millions of honey bees dying in the Baden-Wurttemberg region that runs alongside the Rhine in Germany (see panel).

The approval for some of the Poncho products has since been reinstated in the country. In the UK existing approvals in sugar beet and oilseed rape were not affected, and the product, albeit at a lower rate than in Germany, is also now approved in maize for the first time this spring.

But it wasn’t the first time neonicotinoids have been implicated in bee problems. France banned the use of another neonicotinoid, imidacloprid (Gaucho), in sunflowers in 1999 after heavy bee losses in 1997. Beekeepers in other countries, particularly the USA, have also sent accusatory glances towards pesticides.

With that background it is probably not surprising that last month the Co-operative Group became the first UK retailer to temporarily, at least, prohibit the use of eight insecticides for use on its own brand fresh produce, as part of its “radical” 10-point plan to reverse the decline in British honeybees.

Launching “Plan Bee“, the Co-op said the chemicals had been implicated in honeybee colony collapse and as a precautionary measure it would engage with suppliers to eliminate their usage where possible, and until such time as they were shown to be safe.

One third of the average diet relies on honeybees, Paul Monaghan, head of social goals at the Co-op, says. “But nature’s number one pollinating machine appears to be breaking down and no one for sure knows why. The government has accepted there is a problem, however, we are still not seeing any real recognition that pesticides could be a contributory factor.”

Not surprisingly Julian Little, Bayer CropScience‘s communications and government affairs spokesman, has a different view – one where pesticides are not a main contributory factor.

“There are other problems,” he says. “The primary one is verroa mite, a parasitic mite, which left unchecked means you can lose a colony quickly.

“Unfortunately it has grown resistant to the major treatments, such as, our Bayvarol strips, which are impregnated with insecticide that control mites but is harmless to the bees.

“Resistance is now endemic, which means there is no standard way of controlling verroa.”

Colonies weakened by verroa are also more susceptible to the other main problems for bees, bacterial, viral and fungal diseases, according to Dr Little. “They are also becoming endemic, partly because of climate change.”

Together those issues make up 90-95% of the reasons why bee numbers have declined, he claims.

Pesticides are less of an issue, he reckons. “Of course, if you apply clothianidin directly onto a bee it is not going to be very happy. That’s why you cannot spray clothianidin in the UK – it is only available as a seed treatment.

“But PSD has said when it is applied appropriately there is no hazard to non-target organisms.”

Simon Press, the Co-op’s senior technical manager, agrees there are other factors contributing to colonies collapsing, but says the German incident focused attention on the neonicotinoid insecticides.

In addition, some French research suggested imidacloprid affected communication between bees at sub-clinical levels.

“So we decided partly due to the issues in Germany and because of this research we wanted to take the extra step.”

The Co-op’s policy doesn’t mean growers cannot use the products, he points out. “It is a prohibition, not a ban. We don’t want growers to use them, but if growers do find they have to use them because there are no other chemicals around or for proven resistance management strategies, then they have to ask for a derogation.”

The restrictions also only apply to crops that bees pollinate or forage upon, he stresses. For most mainstream arable growers it would only affect those growing vining peas or potatoes for the retailer.

Dr Little points out the decision to blanket prohibit neonicotinoids is too wide-reaching. “For example, it includes thiacloprid (Biscaya), which is incredibly safe to bees. It even has a label approval for spraying when bees are foraging and flowers are in full view.

“We wouldn’t necessarily encourage that – as a good agricultural practice is it not particularly clever – but the Co-op decision not to allow its use, the chances are the farmer will have to use a more bee-toxic product instead.

“It is unfortunate the Co-op made such a sweeping decision.”

As part of Plan Bee the Co-op has allocated £150,000 for bee research – part of it going towards researching whether neonicotinoids do affect bee communication, Mr Press says. Favourable research could allow the restrictions to be lifted, he stresses.

Dr Little suggests the research could have been targeted better. “Any money going into bee health is a good thing. Good bee health is important for crops – we’re dependent on bees for breeding new oilseed rape varieties, for example.”

“But it is disappointing that the Co-op hasn’t targeted its research at the bigger problems.”

According to Dr Little the Co-op has stipulated the research must be in three areas: Changing agricultural practises, increasing the genetic diversity in bee populations and the impact of pesticides. “At best it is targeting some of the smaller problems. I just feel it is somewhat misdirected.”

DEFRA has also pledged to spend over £4 in trying to improve bee health in the next five years.

What happened in Germany?

The use of treated seed is obligatory over an area of 4000ha in the region affected to prevent western corn rootworm from spreading further.

Maize sowing last spring had largely been finished when the reports of bee losses started coming in. According to Manfred Herderer, the president of the German Professional Beekeepers’ Association, around 50-60% of bees died on average, with some beekeepers losing all their hives.

Not surprisingly the German pesticides approval authority, BVL, reacted swiftly by suspending registration for eight insecticidal seed treatments used in oilseed rape and maize in mid-May.

Investigations found that along with the abrasion of incorrectly treated seed during sowing, the problem was exacerbated by the use of certain types of pneumatic drills and strong winds. The high doses of clothianidin required to control western corn rootworm also contributed, according to Dr Little.

Despite the problem being human error, so far, the German authorities have not re-instated the approval for Poncho Pro in Germany. “We hope it will come in time,” Bayer’s Nigel Adam says.

But Bayer does have approval for a lower dose Poncho for use in the UK on maize. “Its dose is half that of Poncho Pro because we don’t have western corn rootworm.”

Even so, strict stewardship guidelines have been put in place including a stipulation that the correct sticker must be used, which is supplied to the seed treater with the active.

Bayer is also providing help modifying older maize drills to prevent seed dust being from vented into the air. “The drills work on a suction/vacuum system to place the seeds accurately, which means air needs to be extracted and then released through an exhaust system.

“In all but very new drills it is vented upwards, so we are instructing growers and contractors how to modify the drill cheaply to vent the air downwards instead.”

Combining that measure with using the right sticker should reduce dust, in theory, by 100-fold, he says.

German research

A four-year study conducted by German Bee Research Institutes has found that there is significant correlation between winter bee losses and varroa and virus infestations in the autumn.

The study, done in collaboration with bee farmer and keeper organisations and major agchem firms, conducted comprehensive tests of over-wintering losses with around 120 beekeepers and 1200 bee colonies.

Among the factors recorded were apiary site and management details such as colony formation, migration and varroa control, colony size in autumn and spring, honey yield, pest and disease infestation and pesticide residues in bee bread – the main source of food for honeybees and their larvae and made from pollen and nectar collected by worker bees.

Winter bee losses in the study were between 8-16% on average, with marked regional variations – well below losses shown by surveys.

The key finding was that the larger the verroa infestation in the autumn the more likely the hive was to suffer losses.

Trace levels of around 55 different active substances, mostly fungicides, acaricides used to control varroa and herbicides, were found in the 215 analysed bee breads.

But clothianidin was not detected, and imidacloprid only found in one sample close to the level of detection. The study concluded that the data did not indicate any direct harmful effects on bees was to be expected.

It did, however, recognise a suitable method was needed to assess sub-lethal and long-term effects from bees feeding on bee bread with pesticide residues.