A single meal of pesticide-contaminated flowers is enough to seriously damage the health of solitary bees, reducing their longevity and compromising their reproductive capacity. This is the disturbing discovery made by an international study led by the University of Bologna
He is about to end up run over, his mother saves himA single meal of pesticide-contaminated flowers is enough to seriously damage the health of solitary bees, reducing their longevity and compromising their reproductive capacity. This is the disturbing discovery made by an international study led by the University of Bologna.
A single, single exposure, carried out at the end of the winter diapause, a state similar to hibernation, is enough to reduce the life span of these insects and to delay the development of the ovaries.
And the fault is not to be attributed to the single product but to the mix of pesticides today responsible for the frequent die-off of bees. According to the researchers, this should lead to rethinking the risk assessment system of these poisons: today, in fact, only the effects produced by single molecules are considered, but those related to multiple pesticides combined together are rarely considered.
The aim of the new research was therefore to analyze the possible effects produced on Osmia bicornis (also known as Osmia rufa) from two types of pesticides: an insecticide neonicotinoide it's a fungicide. The researchers created a mix containing the two substances in doses comparable to those found in the fields. At that point they fed the compound to the solitary bees. The latter, compared to their peers, do not live in colonies organized in hives, but each single female builds its own independent nest.
"Like the honey bee, solitary bees are also essential for pollination, and they too are disappearing," explains Fabio Sgolastra, researcher at the University of Bologna who coordinated the study. "These are particularly endangered species because, not being organized in numerous societies, the disappearance of a single individual automatically entails the end of an entire line of succession".
The result left no room for doubt. In fact, a single oral exposure to the pesticide mix was enough to significantly reduce the longevity of the insects and delay the development of their ovaries.
“What we have observed is a double negative effect. On the one hand, the life of the bee becomes shorter and on the other the times for the start of egg laying are lengthened: a dangerous phenomenon, which reduces the reproductive capacity of these insects and can end up endangering the survival of the populations of Osmie in agricultural environments, ”said Sgolastra.
Subsequently, the researchers also subjected solitary bees to solutions containing the two pesticides separated from each other, without finding any negative effects.
“The two pesticides, in those quantities and in a single dose, are not harmful. However, when they are together, only one meal at the end of wintering is enough to produce dangerous consequences ".
The die-off of bees
Unfortunately, a problem far from being solved and which worries scientists all over the world. In fact, bees are precious for plant biodiversity: moving from flower to flower to seek nourishment, they favor pollination, thus contributing to the survival and development of plants. Their disappearance, therefore, could have serious consequences on the balance of the ecosystem.
For its part, Europe has provided for the banning some pesticides harmful to bees but it is only a drop in the bucket since there were only 3 banned substances.
The research results were published on Proceedings of the Royal Society B.
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Francesca Mancuso
