One of the most common pesticides in Brazil, imidacloprid neonicotinoide, may be endangering native bees, suggests a study recently published in the journal Environmental Research. However, because it does not have a specific risk assessment protocol for these species, Brazilian scientists are unaware of the real dimensions of the problem.

The warning comes from preliminary results of studies being conducted at the Paulista State University (Unesp) and the Federal University of São Carlos (UFSCar) with the objective of understanding the specific sensitivity of native social bees (Melipona scutellaris and Scaptotrigona postica) and solitary (Tetrapedia diversipes and Centris analis) to these compounds.

The research is supported by FAPESP through two projects (17/21097-3 and 19/27863-5).

In laboratory tests, bees are exposed to pesticides, used in cotton, potato, sugarcane, beans and tomatoes crops, among others. Diluted in environmentally relevant concentration, that is, similar to what would be found in nature, the chemical is applied orally (simulating the collection of food resources such as pollen, nectar, floral oils and resins) and by contact (as happens in spray clouds during the application of the product in crops).

Then, factors such as insect behavior (e.g., the ability to perform habitual pathways, response to light and level of disorientation), cell markers, and mortality are evaluated.

In the case of solitary bees, the authors say, the studies are even more incipient and include the extra challenge of lack of knowledge about the biology of the animal.

"We still know little about their life cycle and habits, so it is necessary to first create the species in the laboratory and then propose an appropriate protocol," explains Osmar Malaspina, professor at the Institute of Biosciences at Unesp in Rio Claro.

Preliminary results of studies with solitary bees have indicated that they may be affected by pesticides even at low concentrations. "We can already see worrying effects of poisoning, such as tremors and flight inability," says Rafaela Tadei, a doctoral student in biological sciences at Unesp under the guidance of Malaspina and co-author of the paper. "If the bee were in nature and not in the lab, it would be preda and die."

Evaluations made on the fatty body of these solitary bees, part responsible for detoxification and which also serves as a reserve of nutrients, indicate that this structure is being affected, which can compromise physiological functions.

Lack of protocol

Today, worldwide, the risk assessment of pesticides for bees uses as reference one of the most common species in the world, the honey producer Apis mellifera. In Brazil, where there are about 3,000 native species, for which there are no specific models, the international standard is extrapolated with a safety factor of ten, which is also based on non-Brazilian species. However, according to studies by Unesp and UFSCar, even this extra measure of caution does not seem to be sufficient to ensure the protection of insects, which reinforces the need for specific protocols and improvements in regulation.

"When we use a less sensitive model species as the default, we assume that bees are safe when, in fact, they may not be," explains the researcher. "And although further studies are needed to know how much pesticides affect the reproduction of Brazilian bees and the pollination service carried out by them, we know that the decrease in the pollinator population will be reflected in the reduction of food diversity, affecting the economic system and, consequently, society," says Tadei.

"Studying the effects of pesticides on bees allows us to look for ways to preserve our biodiversity and identify what is happening to these populations so that it is not too late to recover them and we start relying on manual pollination or other means that will greatly enlivece our food resource."

According to Tadei, the next step in the studies will be the inclusion of three spheres in this debate: civil society, so that it understands the need for research and protection of the environment; government agencies to improve regulation based on scientifically proven data; and the scientific community, so that it works together and obtains the best answers for the environment.

The paper Are native bees in Brazil at risk from the exposure to the neonicotinoid imidacloprid? can be read here.

Source: Um só Planeta