Brazilian bees are more sensitive to pesticides – 03/30/2023 – Environment

The native uruçu northeastern bees (Melipona scutellaris), jataí (Tetragonisca angustula) and Mandaguari (Scaptotrigona postica) are more sensitive to the pesticide TMX (thiamethoxam) than to Apis mellifera —species with sting introduced in the country and adopted as a model for toxicological tests for the approval of agricultural pesticides.

This is what a study carried out by researchers from UFSCar (Federal University of São Carlos) in partnership with Unicamp (State University of Campinas) and Unesp (São Paulo State University) showed. By evaluating, for the first time, the impact of TMX on the three native and stingless species, the study offers subsidies for the elaboration of public policies aimed at the protection of pollinating insects in Brazil.

The reduction in bee populations, in addition to being a serious environmental problem, has negative repercussions on agricultural productivity.

“Brazil has more than 2,000 species of bees. Among the stingless bees, there are almost 500 species. It is an enormous diversity”, says Osmar Malaspina, professor at the Institute of Biosciences at Unesp in Rio Claro and coordinator of the Research Group on Ecotoxicology and Bee Conservation and the Working Group for the Development of Methods for Toxicity Testing in Brazilian Native Bees with the International Commission for Plant-Polinator Relations (ICPPR).

“Of course, it is not possible to carry out a toxicological test on all of them and with all the pesticides, but it is necessary to select some species, in addition to the Apis melliferato understand how it is possible to create a better configuration for the protection of these insects in the country.”

The study, supported by Fapesp under the Biota Program and published in the journal Environmental Pollution, is part of a larger project whose objective is to broaden understanding of the impact of the use of pesticides on the population of native stingless bees (also called indigenous bees) and support the creation of new protocols and laws related to the use of agricultural pesticides in the country.

This is because, currently, the toxicological tests that are part of the risk assessment of pesticides follow the guidelines established by the Organization for Economic Cooperation and Development (OECD) and are practically restricted to the species A. mellifera as a biological model.

However, the debate about the need to reassess the environmental risk of pesticides has grown in recent decades, especially in tropical and subtropical regions, where there is a greater diversity of bee species.

“Stingless bees are highly affected by pesticides, but tests are usually done only with the A. mellifera, which is a stinging species that was introduced in Brazil. It is a species of European origin”, explains Roberta Cornélio Ferreira Nocelli, professor at the Center for Agricultural Sciences at UFSCar in Araras, coordinator of the Working Group for the Development of Methods for Toxicity Tests on Brazilian Native Bees at ICPPR.

In the recently published study, the researchers performed a sensitivity curve to compare the impact of the pesticide in different scenarios, in addition to assessing the sensitivity to TMX per bee gram, since the size varies between species.

“The results showed that the A. mellifera is more tolerant to TMX than the three stingless bee species in all the scenarios we evaluated”, explains Ana Paula Salomé Lourencetti, first author of the article.

“Since we created a sensitivity curve, it is possible to analyze different scenarios as well, as we take into account the weight of the bee and other parameters related to pesticide consumption. This is because there are some differences in toxicity when only consumption is taken into account or consumption and the weight,” she says.

Thus, in relation to the average lethal concentration determined for the three species of stingless bees, TMX proved to be more harmful to uruçu, followed by jataí, mandaguari and finally the A. mellifera.

Already the analysis of the average lethal dose and taking into account the weight of the bees (dose per microgram), M. scutellaris was the most sensitive, followed by S. postica, T. angustula It is A. mellifera.

In the average lethal dose analyzes without taking into account the weight of the bees, the T. angustula was the most sensitive, followed by M. scutellaris, S. postica It is A. mellifera.

“The results of the work show that, for some species, the A. mellifera may be considered a good parameter, but not for others. Therefore, it is an indication that we need to evaluate more carefully the toxicity tests aimed at releasing pesticides, as they are not being 100% efficient in protecting Brazilian native bees”, says Nocelli.

Public policy

Previous studies had already shown that the sensitivity of bees to pesticides varies according to size, life cycles, metabolism, behavior, biology and routes of exposure. For this reason, the researchers point out, the extrapolation of toxicity data referring to the A. mellifera for other species of bee social and solitary behavior has been questioned for years.

In relation to stingless bees, in addition to these issues that confer greater sensitivity, the risk occurs because they are abundant species in crops and extremely exposed to pesticides.

For these reasons, the group of researchers is developing a new protocol (in the process of being standardized) for stingless bees, which contains possible biological models for the environmental risk assessment process.

The work, coordinated by the researchers and funded by CNPq (National Council for Scientific and Technological Development), is intended to expand toxicological tests on a greater number of bee species to subsidize the approval and renewal of registration of pesticides.

“IBAMA [Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis] has a risk assessment system that is unique for bees in Latin America. However, it is very similar to the one adopted in Europe and the United States for registration of pesticides”, says Nocelli.

“That’s why we are working together with environmental agencies to create a protocol that covers toxicity tests on native stingless bees. Public policy has to be based on a standardized protocol and we didn’t have that yet for native species .”

The researcher explains that, currently, in addition to A. melliferathere is a protocol for three other species (terrestrial bombs, Osmia cornuta It is osmia lignaria).

“However, these are also from the Northern Hemisphere. Of the three species included in the protocols, none is native to Brazil. And one of our major questions is whether these tests carried out with the A. mellifera guarantee the safety of our bees”, he says.

The initiative to develop new protocols that consider native species is a pioneer in Latin America. “This is a complex problem that needs to be resolved. In this case, Brazil is at the forefront. Even the legislation that requires testing with A. mellifera is the only one in South America. This only exists in the United States and Europe”, emphasizes Malaspina.

“Now it is necessary to move forward in this issue of native stingless bees, because most of these species are native, they do not exist in the northern hemisphere. It is in our interest, as they are extremely important in terms of pollination. We need legislation to protect them” , concludes the researcher.

The article Surrogate species in pesticide risk assessments: Toxicological data of three stingless bees species can be read here.