A threat to bees

Contamination by pesticides puts native bees at risk

Por: PUCRS Magazine No.3 Annual Issue in English/2016

The populations of bees have been on a considerable decline all over the world. This is mostly due to human actions such as habitat fragmentation, the use of natural environments as agricultural or urban areas, and the use of pesticides, which compromise the abilities of feeding, navigation, memory and return to hives. This issue has been addressed and given proper attention by specialists and now unprecedented results from research carried out at PUCRS have been revealed: in addition to these known damages, pesticides may alter the castes in the colonies, as is the case with some Plebeia droryana stingless bees that were supposed to be queen but turned into workers. In the long run, this may lead to the extinction of some species.

The study coordinated by the director of the Institute for the Environment (IMA) and professor of the School of Biosciences, Betina Blochtein, in an initial stage, conducted tests using six different concentrations of pesticide Chlorpyrifos, used in Brazil to fight off insects considered to be agricultural plagues. The materials used in the dosage administered in the bees’ foods were collected from the nature, according to previous scientific publications. Every tested concentration was much smaller than the commercially recommended dosage for the product use, as it would only simulate residual contamination in plants visited by the bees rather than direct application.

 

The effect of pesticides

The concern with the effects of pesticides is due to the fact that this group of stingless native bees relies on only one queen per nest. The administration of higher dosages will cause death, and of lower, sub-lethal ones will cause damages that compromise future generations. In this group of stingless bees, natural reproduction is low, there are few colonies per hectare and the density of nests is low. “If a hive is not able to produce new queens, in the medium run, it will become extinct. In the absence of a queen to replace that one that is aging, or even queens that could form new colonies and reproduce, we are talking about damages to populations in the medium run, since they tend to decline or even die out”, claims Betina.

All tests were carried out in a laboratory, with bees bred at the Center of Experimental Biological Models of PUCRS (CeMBE). Another highlight of this study is the heterogeneity of the group, formed by an undergraduate research grantee, a doctoral student, a post-doc researcher and a professor, all of whom of distinct academic levels of the University, as well as a collaborator from USP.

 

Next steps

The initial stage of the study conducted tests with organophosphorates. Chlorpyrifos is widely used in Brazil, but has been banned in both the USA and Europe for the damages it causes to bees. Now, the team’s intent is to study the effects of another group of popular products, the neocotinoids. They have a different mechanism of operation and are more popular all over the world. They can be injected onto the plant’s seed, without the need for spraying. “We want to see the effects on adults, any behavioral alterations, and also whether the queen can mate, lay eggs and how long they will live”, explains Charles Fernando dos Santos, a post-doc grantee (PNPD/Capes) from the Graduate Program in Zoology. Some countries are trying to ban it.

To find out more about it, please visit PUCRS Magazine 2016 annual issue