A recent study to be published in June’s edition of Bulletin of Insectology has put the pesticide imidacloprid firmly centre stage as a leading cause of colony collapse disorder. The study shows that even very low levels of the pesticide can kill up to 94% of hives.
94% of hives succumbed to colony collapse disorder.
The research team from Harvard School of Public Health (HSPH), led by Alex Lu, associate professor of environmental exposure biology in the Department of Environmental Health, monitored 16 different hives over a 23 week period. Groups of hives were treated with imidacloprid at various levels – including levels below that used on crops. The results were remarkable. 15 of the 16 hives succumbed to colony collapse disorder – where adult bees abandoned their hives.
It apparently doesn’t take much of the pesticide to affect the bees. Our experiment included pesticide amounts below what is normally present in the environment.
The study showed that all the hives, no matter how high the concentration of imidacloprid was, were still operating as normal after 12 weeks but within 23 weeks the hive collapse had reach 94% or 15 of the 16 hives.
Signs from hives were typical of colony collapse disorder.
The hives with the highest levels of imidacloprid collapsed first. The signs found at the hives were typical of signs found in normal hives that had collapsed – the hives were empty except for food stores, some pollen and young bees. If a hive collapses due to parasites or disease then bee-keepers normally find dead adult bees in and around the hive.
“The significance of bees to agriculture cannot be underestimated,” says Lu. “And it apparently doesn’t take much of the pesticide to affect the bees. Our experiment included pesticide amounts below what is normally present in the environment.“
Bee-keepers could be inadvertently preparing their hives to collapse.
While many bees will come into contact with the pesticide during their nectar gathering activities in the wild there is also the concern that bee-keepers could be inadvertently dosing the hives with low levels of the chemical. Many bee-keepers will feed their bees corn-syrup as supplemental food when needed. With most US corn being treated with imidacloprid the corn syrup will also contain the chemical.
Imidacloprid is the most widely used insecticide in world.
Imidacloprid is a widely used pesticide – some estimates put it at the most widely used insecticide in the world – with licenses for use in over 120 countries. In the UK it was licenced for use in 1993. It is used to tackle pests in the soil, on the foliage of plants and also protection of seeds. In the UK it is used on a wide range of produce from apples through to sugar beet and potatoes.
But it’s not just commercial farmers that use imidacloprid. Many domestic gardening products use the insecticide as well as de-fleaing powders and treatments that pet owners will use.
Harvard School of Public Health. Use of common pesticide linked to bee colony collapse.
Harvard School of Public Health. Chensheng (Alex) Lu.