Pesticides cause of bee mortality

Insecticides cause disappearance of bee colonies

02/04/2012

Scientists and beekeepers have been observing massive bee mortality for years. There were already several triggers such as certain mites and parasites under suspicion. Now, Scottish researchers at the University of Stirling have found that pesticides used by humans appear to play a bigger role than previously thought.

Researchers from the School of Natural Sciences at the University of Stirling (UK) found that the presence of nectar and pollen in the so-called neonicotinoids (highly effective insecticides) also causes significant damage to the propagation of bumblebees. The animals were increasingly suffering from malformations, the affected colonies grew much slower and the production of new queens was reduced by 85 percent, report Dave Goulson and colleagues in the journal „Science“. In addition, French researchers have found that the applied pesticides also affect the sense of insect orientation, preventing them from returning to their canes.

Pesticides decide on bumblebee and bee mortality
Both the results of the French researchers and the results of Dave Goulson and colleagues suggest that pesticides play a much greater role in the bumblebee and bee deaths seen for years than previously thought. The two independent in the trade magazine „Science“ Presented studies show that the insecticides have a significant influence on the observed decline in bee and bumblebee populations. The Scottish researchers had studied the effect of pesticides on the development of bumblebees, exposing the animals to concentrations similar to those found in the pollen and nectar of sprayed crops. The researchers then let the bumblebee keep its nest for six weeks and then checked how much the nests weighed with the entire contents of bumblebees, wax, honey, larvae and pollen.

Pesticide contaminated colonies grow less
The researchers found that the colonies on pesticide-contaminated animals were on average 8 to 12 percent smaller than in the control group. In addition, the bumblebees tended to malform and the strained peoples produced 85 percent fewer queens, write Dave Goulson and colleagues. The queens are crucial for the reproduction of the bumblebee in the following years, so that the insecticides here also show a delayed effect, which becomes noticeable only one year after the actual pesticide load. The number of queens is directly related to the number of new nests in the coming winter, the Scottish scientists report. In Dave Goulson's view, insecticides have a massive impact on the observed decline in bumblebee populations worldwide. „Some bumblebee species have declined enormously“, stressed the expert, calling North America an example of where „some species more or less completely disappeared from the continent“ are. In the United Kingdom, three species have been eradicated, according to Goulson. „Given the extent of use of neonicotinoids“, It can be assumed that the pesticides have a significant share in the mass extinction of bumblebees and bees, so the assessment of the Scottish researchers.

Pesticides influence the sense of orientation of bees
The study of French researchers led by Mickael Henry of the National Agricultural Research Institute in Avignon also suggests that the pesticides have a serious impact on the bee and bumblebee populations than previously thought. As part of their study, Henry and colleagues attached tiny microchips to the bodies of bees to track the animals' flight-rod. After some of the experimental bees came into contact with the insecticide thiamethoxam, their sense of direction seemed to be significantly impaired, write the French researchers. The affected animals died two to three times more often far away from their nest than bees that did not come into contact with the insecticide, Henry and colleagues said. The flight paths determined by the data from the microchips showed that the contaminated bees eventually reached a distance from their nest that made their return difficult. Thus, the human-sprayed toxins could contribute to the fact that a growing proportion of the bee does not find its way back to his stick, so the conclusion of the French researchers.

Food crisis due to bee mortality?
The decline in bee and bumblebee populations has led to intense discussions over the possible causes and consequences of bee or bumblebee death in recent years. Because the beneficial insects play a crucial role in the ecosystem. They pollinate billions of plants and thus ensure that they can bear fruit or reproduce. Lacking the bees, this could trigger a global food crisis, according to the United Nations (UN). Also as an economic factor, the performance of insects is of considerable importance, as large parts of agriculture would not work without their contribution. In the long term, in the absence of bees, the plant's nutritional base could continue to dwindle, massively reducing the availability of food. An adequate supply of the population would not be guaranteed without the support of the beneficial insects.

Long-term yield losses through the use of pesticides
The search for the causes of the worldwide bee mortality is therefore in full swing, whereby in addition to the insecticides or pesticides especially the aggressive Varroa mites are suspected as triggers. The mites bite on the bees and can lead to the death of the animals. In the canes, the mites can easily multiply, which may involve the loss of entire peoples. As the mites stay active longer and spread better during the relatively mild temperatures, the weather also plays a role in the increased bee mortality, according to the experts. Furthermore, special parasite flies are suspected of favoring the dying of bees. However, the current study results suggest that the pesticides used by humans have a far greater share of bee mortality than previously thought. Here, for reasons of simple interest, a rethinking should take place as soon as possible. Because the yield increases that can be achieved in the short term with the help of pesticides can quickly lead to considerable yield losses if the bee populations continue to decline. (Fp)

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