Honeybees

Recent declining numbers of honeybees, Apis mellifera, in colonies threatens crop production as well as feral plant community biodiversity. Chemicals applied in agroecosystems are regarded as one of primary causes of the decline. In Japan, the heavy loss of honeybee colonies associated with pesticide use has been reported from beekeepers recently, leading to lessened use of honeybee colonies to facilitate pollination of cultivates. Nevertheless, no study has quantitatively examined the damage to honeybee colonies caused by the pesticide application in Japanese agricultural fields to date.

Researchers from Mainz University Medical Center and Goethe University Frankfurt discovered that the use of active systemic insecticides called neonicotinoids causes the alarming bee mortality. The study was published in the journal PLOS ONE. It is led by Professor Ignatz Wessler of the Institute of Pathology at the University Medical Center of Johannes Gutenberg University Mainz and collaborated with Professor Bern Grunewald of the Bee Research Institute at Goethe University Frankfurt and other colleagues.

While pesticide companies and some researchers say the tiny Varroa mite is the main culprit in declining honeybee health, new Dutch research concludes that bees are more vulnerable to mites and other stressors because of their constant diet of neonicotinoid insecticides. The debate about what's killing honeybees and other pollinators has continued for several years, with Varroa mites largely taking the blame for colony collapse disorder.

Neonicotinoids are implicated in the decline of bee populations. As agonists of nicotinic acetylcholine receptors, they disturb acetylcholine receptor signaling leading to neurotoxicity. Several behavioral studies showed the link between neonicotinoid exposure and adverse effects on foraging activity and reproduction. However, molecular effects underlying these effects are poorly understood. Here we elucidated molecular effects at environmental realistic levels of three neonicotinoids and nicotine, and compared laboratory studies to field exposures with acetamiprid.

A strong immune defense is vital for honey bee health and colony survival. This defense can be weakened by environmental factors that may render honey bees more vulnerable to parasites and pathogens. Honey bees are frequently exposed to neonicotinoid pesticides, which are being discussed as one of the stress factors that may lead to colony failure.

The decline of pollinators worldwide is of growing concern and has been related to the use of plant protecting chemicals. Most studies have focused on three neonicotinoid insecticides, clothianidin, imidacloprid and thiamethoxam, currently subject to a moratorium in the EU. Here we focus on thiacloprid, a widely used cyano-substituted neonicotinoid thought to be less toxic to honey bees and of which use has increased in the last years. Honey bees (Apis mellifera carnica) were exposed chronically to thiacloprid in the field for several weeks at a sublethal concentration.

In a new study that would seem to complicate the problem of saving honeybees and other pollinators, Indiana researchers have found that bees get only a minor part of their big pesticide burden from crop treatments — even in landscapes dominated, like Minnesota’s, by corn and soybean fields. Although neonicotinoid insecticides have received the most attention as a driver of beekeepers’ colony losses, it has long been known that honeybees examined post mortem are carrying a host of other pesticides.