Honeybees

Two studies published in Nature last week have raised more concerns about whether neonicotinoid pesticides adversely affect bee health. One study shows that bees are drawn to neonicotinoids, possibly because the insects catch a “buzz” from the pesticides similar to the one humans get from nicotine (2015, DOI: 10.1038/nature14414). The other study suggests that neonicotinoids affect bee behavior and growth under realistic conditions in a crop field (2015, DOI: 10.1038/nature14420).

We studied the effects of sublethal doses of imidacloprid on olfactory learning in the native honey bee species, Apis cerana, an important pollinator of agricultural and native plants throughout Asia. We provide the first evidence that imidacloprid can impair learning in A. cerana workers exposed as adults or as larvae. Adults that ingested a single imidacloprid dose as low as 0.1 ng/bee had significantly reduced olfactory learning acquisition, which was 1.6-fold higher in control bees. Longer-term learning (1-17 h after the last learning trial) was also impaired. Bees exposed as larvae to a total dose of 0.24 ng/bee did not have reduced survival to adulthood. However, these larval-treated bees had significantly impaired olfactory learning when tested as adults: control bees exhibited up to 4.8-fold better short-term learning acquisition, though longer-term learning was not affected.

The Ontario government has unveiled North America’s first agricultural restrictions on a widely used class of pesticides blamed for the decline in bees and other pollinators.The controversial regulations aimed at reducing the use of neonicotinoid insecticides made by Bayer AG and Syngenta AG by 80 per cent within two years goes into effect on July 1. The province said on Tuesday it wants to reduce the overwintering death rate of honey bees to 15 per cent from an average of 34 per cent by controlling the planting of seeds treated with the three most commonly used neonicotinoids. Glen Murray, Ontario’s Minister of the Environment, said the rules are “highly workable” and address farmers’ concerns while reducing damage from neurotoxic pesticides that are persisting in streams and soil and affecting everything from birds and bees to butterflies and aquatic life. The rules, which are intended to improve the health of insects responsible for pollinating about $900-million worth of crops, require that farmers who use neonic-treated seeds to grow corn and soybeans show they have insect problems, and that seed vendors be licensed. Vendors of other pesticides require licences, and the new Ontario rules simply add neonics to that regime, he noted. Establishing, administering and enforcing the licensing and planting system will cost $3-million to $4-million a year, said Mr. Murray, conceding there is little to prevent anyone from purchasing the treated seeds in the United States.

In a recent issue of the journal Science, Dave Goulson and colleagues presented a review entitled “Bee declines driven by combined stress from parasites, pesticides, and lack of flowers”. This stimulated Jaboury Ghazoul to submit a letter to Science criticising the Goulson et al. paper from a number of perspectives, but particularly the paucity of the evidence base for pollinator declines. Dave and his co-authors robustly responded to that letter, as you might imagine. In some respects this was an unsatisfactory exchange, however, as the focus was largely on agricultural pollinators, rather than pollinators of all plants (including the majority non-cultivated species) and I think that (perhaps with more space?) Dave could have outlined the evidence in more depth. The most striking statement in Jaboury’s letter was that the “evidence for pollinator declines is almost entirely confined to honeybees and bumblebees in Europe and North America”. Now, even given the fact that Jaboury was possibly referring specifically to agricultural pollinators, that is a very extreme statement to make. Underlying it is the suggestion that global concerns about declining pollinator biodiversity (a subject I’ve discussed repeatedly on this blog) is underpinned by a taxonomically and geographically thin evidence base. Is that really true? I don’t believe so and I think it’s worth presenting a brief overview of the evidence, not least because Dave’s review and the resulting correspondence is pay-walled at the Science site (though if you Google the titles you might, just might, find copies posted on the web…).

Thirty-two honeybee (Apis mellifera) colonies were studied in order to detect and measure potential in vivo effects of neonicotinoid pesticides used in cornfields (Zea mays spp) on honeybee health. Honeybee colonies were randomly split on four different agricultural cornfield areas located near Quebec City, Canada. Two locations contained cornfields treated with a seed-coated systemic neonicotinoid insecticide while the two others were organic cornfields used as control treatments. Hives were extensively monitored for their performance and health traits over a period of two years. Honeybee viruses (brood queen cell virus BQCV, deformed wing virus DWV, and Israeli acute paralysis virus IAPV) and the brain specific expression of a biomarker of host physiological stress, the Acetylcholinesterase gene AChE, were investigated using RT-qPCR. Liquid chromatography-mass spectrometry (LC-MS) was performed to detect pesticide residues in adult bees, honey, pollen, and corn flowers collected from the studied hives in each location. In addition, general hive conditions were assessed by monitoring colony weight and brood development.