One of the most common pesticides in Brazil, the neonicotinoid imidacloprid, may be putting native bees at risk, suggests a study recently published in the journal Environmental Research. However, as they do not have a specific risk assessment protocol for these species, Brazilian scientists are unaware of the real dimensions of the problem.
The alert comes from preliminary results of studies being conducted at the Universidade Estadual Paulista (Unesp) and at the Federal University of São Carlos (UFSCar) with the aim 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 investigation is supported by Fapesp through two projects (17/21097-3 and 19/27863-5).
In laboratory tests, bees are exposed to pesticides, which are used in cotton, potato, sugarcane, beans and tomato crops, among others. Diluted in an 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 in clouds of spraying during application of the product on crops).
Then, factors such as insect behavior (eg, ability to perform habitual paths, 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 added challenge of a lack of knowledge about the animal’s biology.
“We still know little about their life cycle and habits and, therefore, it is necessary to first create the species in the laboratory and then propose an appropriate protocol”, explains Osmar Malaspina, professor at the Unesp Institute of Biosciences in Rio Claro.
Preliminary results of studies with solitary bees have indicated that they can be affected by pesticides even in low concentrations. “We can already observe worrying effects of poisoning, such as tremors and inability to fly”, says Rafaela Tadei, a doctoral student in biological sciences at Unesp under the guidance of Malaspina and co-author of the article. “If the bee were in the wild and not in the laboratory, it would be preyed upon and it would die.”
Evaluations made on the fat body of these solitary bees, part responsible for detoxification and which also serves as a nutrient reserve, 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 a 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 precautionary measure does not seem to be enough to guarantee the protection of insects, which reinforces the need for specific protocols and regulatory improvements.
“When we use a less sensitive model species as a standard, we assume that the bees are safe when, in fact, they may not be”, explains the researcher. “And, although more studies are still needed to know how much pesticides affect the reproduction of Brazilian bees and the pollination service performed by them, we know that the decrease in the population of pollinators will be reflected in the reduction of food diversity, affecting the system economy 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 to depend on manual pollination or other means that will make 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 environmental protection; government bodies to improve regulation based on scientifically
proven; and the scientific community, so that they work together and obtain the best answers for the environment.
The article “Are native bees in Brazil at risk from the exposure to the neonicotinoid imidacloprid?” (“Are Brazilian native bees at risk of exposure to neonicotinoid imidacloprid?”) can be read here.
