Yet another study is blaming neonicotinoids for causing bee deaths. But it’s not from direct contact with the world’s most widely-used agricultural chemical, it’s because neonic exposure leaves bees vulnerable to parasitic infections and viruses.
The international review by Francisco Sánchez-Bayo at the University of Sydney and Nicolas Desneux of INRA in France looked at the correlation between bee deaths and a world-wide increase in neonicotinoid use. In some countries like the USA, bee colony loss is around 40% per year, as against a normal loss of 10-15%. Although exactly how neonics cause bee death is still unclear, the neonic use also correlates with a much higher incidence of parasitic infections from Varroa mite and also Nosema ceranae and a higher rate of viral diseases like deformed wing virus.
Although its true that there have been other insecticides used before neonics, these were typically fat soluble and killed insects only by contact, which did result in many deaths among non-target insects when they were sprayed. In contrast, neonics are water soluble and are translocated around the plant but this means that insecticidal residues end up everywhere, including the pollen and nectar which bees both consume on the plants and also take back and store in the hive as honey.
What the research review also identifies is that sub-lethal doses of neonics like imadacloprid (banned in several USA states and across Europe but still sold and used by home gardeners in Australia) suppress a bee’s immune systems leaving it very vulnerable to virus attack.
The study co-author Francisco Sánchez-Bayo is unequivocal:
“systemic insecticides are the ultimate cause of this complex crisis of honey bee health”
Neonicotinoids and the prevalence of parasite and disease in bees
Francisco Sánchez-Bayo and Nicolas Desneux, Bee World, Volume 92, Issue 2, 2015.
* Read the full article online:http://tandfonline.com/doi/abs/10.1080/0005772X.2015.1118962