Bee deaths: causes, distribution and consequences

Bee deaths: causes, distribution and consequences

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Bees are humming less and less

Do you wonder if it's quiet on your flower beds this year? In the winter of 2016/2017, many thousands of bee colonies died - up to 3,000 in the small Saarland alone, or 20% of the population. There are two reasons for dying: a mite and pesticides.

The Varroa mite

The Varroa mite is currently the mortal enemy of the bees. It originally came from Asia and had adapted to the bees there. About 40 years ago, imported bees brought the parasites to Europe. The mite attacks the brood of the bees, sucks the blood of the larvae and transmits epidemics. She doesn't like harsh cold or high heat. The mild December 2016 was ideal for the plague.

The beekeeper becomes a exterminator

Protection against the mite is possible, but it requires professional training: in Switzerland, for example, beekeepers give oxal every year in late summer and early winter - like bee acid to bee colonies.

Fall in wild bees

The population of wild bees is currently falling particularly dramatically. Above all, they are poisoned by pesticides. They also lose their habitat and food crops. Almost half of several hundred wild bee species are on the red list.

Habitat loss and the loss of food crops are indirect causes of this decline - the neonicotinoids are a direct killer. These pesticides destroy the bees' brain processes and their communication, navigation and ability to collect pollen.

If the bees are damaged by these poisons, they take fewer collecting flights and can hardly orient themselves. They take longer to reach the beehive. Even tiny amounts of these neonicotinoids, which are far below the limit values, disable bees, bumblebees and other insects, the Berlin neurobiologist Randolf Menzel found.

A French study led by Mickael Henry confirmed Menzel's result: the scientists exposed rape that they had stained with neonicotinoids. It was found that the number of workers' deaths skyrocketed.

However, the bee colonies can compensate for this: They then hatch more female bees and fewer drones, whose task is only to fertilize the queen. In the long run, however, this will lead to genetic impoverishment because fewer and fewer males can pass on their genes.

Not only do bees die

Long-term studies by the British Center for Ecology and Hydrology showed in 62 wild bee species in 2016 that the population shrank radically, since 2002 neonicotinoids have been approved. Wild bees specializing in oilseed rape treated with these pesticides suffered 20% losses.

A California study shows that the same applies to butterflies. Since the poisons were used there, the number of butterflies of various species has decreased significantly.

Bumblebees use fewer poisons to form queens, solitary bees do not build nests, and mating wasps stop working.

Addictive substance for bees

Bees don't avoid the poison, but prefer to seek it out. They even prefer sugar solutions containing these pesticides to pure sugar solutions.

Therefore, they absorb a disproportionate amount of the pollutants. The reason for this is that neonicotinoids act in a similar way to nicotine in humans in the nervous system of bees. In other words, the bees become addicted.

British researchers led by Geraldine Wright from Newcastle University therefore demand that the use of these pesticides must be controlled in order to protect the bees from harm.

An insect trap

The "neonis" have a half-life of 1000 days. The plants only absorb 5% of the toxins, the rest goes into the soil. In addition, these pesticides are water soluble. Therefore, they spread with the rain.

Even flower strips on the edges of fields, which are supposed to protect the insects, are poisoned in this way. Sometimes the pesticide values ​​are even higher than on the crops.

An issue for the EU

The topic of neonicotinoids has now reached the responsible EU Commission. Since valid studies by the EU's internal scientists are available, the corresponding products from Bayer and Syngenta can be banned. It would be Clothianidin, Imidacloprid and Thiamethoxam.

So far restrictions already apply, so the manufacturers have to provide evidence that justifies the approval. If stricter rules now came into force, the corresponding neonicotinoids would only be used in greenhouses.
Green MEP Martin Häusling says: "It is a milestone for bee protection if the EU Commission actually proposes a complete ban on neonicotinoids."

Exact proof from Poland

Polish veterinarians have been able to demonstrate which of the pesticides and bee treatment products cause bee death. Bee poisoning was mainly caused by chlorpyifos, dimethoat and clothianidin.

Complicit in antibiotics?

However, it is probably not only the pesticides alone that have caused bee mortality in recent years. American scientists found that the antibiotic tetracycline also killed the bees.

Nancy Moran of the University of Austin, Texas, suspects that this agent appears to kill beneficial gut bacteria that protect insects from the harmful Serratia bacteria. Because the number of Serratia bacteria was increased in the bees that were treated with the antibiotic. Beekeepers use tetracyclines to protect bee larvae from American foulbrood.

However, the remedy is not an explanation for the death of bees in Germany, because the use of antibiotics in beekeeping is prohibited in Germany.


The insects are also threatened by monocultures. The situation is best in the cities, where allotments, balconies and parks offer a variety. Maize, on the other hand, is as nutritious for the bee as the surface of the moon.

No apples without bees

In 1990 there were still around 1.2 million bee colonies in Germany - today there are 650,000. The wild bees also look grim: Around half are threatened or have disappeared. The extinction of bees has fatal consequences for humans, because 80% of all plants are pollinated by bees. No apples without a bee.

Pesticides and parasites

A study by the University of Vienna identified secondary infections, viruses, bacteria and parasites as responsible for the majority of deaths, for example a virus that causes wing deformation.

The pesticides are not innocent. The bee's immune system is weakened by plant toxins. The pathogens are transmitted from bee to bee, without adequate immune protection, they become ill and die

In Austria, for example, 95% of the toxins applied go into the soil, and these pesticides in particular have reduced the total population of insects by 80% in ten years. Instead of 58 wild bee species, there are now 14.

Bee pastures

If you have a small garden, you can help the bees and create a bee pasture. Flax, clover, bee lover, borage, cosmea, dyed chamomile and buckwheat are particularly suitable for this. Something always blooms from spring to autumn. Early bloomers like liverwort or dead nettle help insects before the fruit trees bloom.

Flowering shrubs are also ideal as a pasture for bees, and they not only feed bees, but also other insects and birds. They also offer birds nesting places. Home-grown plants for such a bee paradise are, for example, wild roses, elderberry, hawthorn, sloe, rock pear, rowan berry, quince, cornell cherry, sea buckthorn or goji berry. After flowering, birds eat the valuable fruit. (Dr. Utz Anhalt)

Polish study:
Tomasz Kiljanek et al. Multi-residue method for the determination of pesticides and pesticide metabolites in honeybees by liquid and gas chromatography coupled with tandem mass spectrometry — Honeybee poisoning incidents, Journal of Chromatography A (2016). DOI: 10.1016 / j.chroma.2016.

Author and source information

Video: Marla Spivak: Why bees are disappearing (August 2022).