A joint study between two faculties of the UBA found that the presence of this agrochemical in the food of the larvae had a negative impact on their survival by delaying their growth and reducing the size they reach as adults.
The honey bee is the main pollinator of many agricultural crops. In the fields, the insect must live with a large amount of agrochemicals in the environment. However, there is little research that addresses the impacts of these compounds on the pollinator. In this context, a study by the Faculties of Agronomy of the UBA (FAUBA) and of Exact and Natural Sciences of the UBA (FCEN) analyzed the effect of the herbicide most used in the world, glyphosate, on the development of the larvae of this bee.
“The herbicide is applied in agroecosystems to prevent weeds from reducing crop yields. When bees feed on flowers, they often carry glyphosate to the hive. So, the moment the larvae hatch inside the comb, they ingest honey with traces of this agrochemical. We wanted to see how this affects its development ”, explained Jorge Zavala, professor in the Chair of Biochemistry at FAUBA and researcher at the INBA institute (UBA-Conicet).
“For that, we raise bee larvae in the laboratory and feed them with glyphosate, a situation similar to what could occur in an agricultural environment. What we found was that the larvae developed more slowly; that is, many of them took longer to become adults and reached lower weights than those who did not ingest glyphosate. These results show that, even when the doses we used were not lethal, the long-term consequences would be negative for the survival of the bees ”, warned Walter Farina, professor at the Department of Biodiversity and Experimental Biology at FCEN and researcher at the Institute of Physiology, Molecular Biology and Neurosciences (FCEN-UBA / IFIBYNE-Conicet).
Based on the study published in the journal Plos One, which arose from Diego Vázquez's (IFIBYNE-Conicet) doctoral thesis, Walter pointed out that as they grow more slowly - up to 40% - some bees may not reach adulthood, and if they could, they would do it with a small size - up to 30%. This implies lower levels of reserves and an impoverished immune system, which reduces the probability that the hive will survive periods of low resources and can alter its population dynamics.
However, Zavala clarified that even though the genetic information within the hive was the same, the bees responded differently to the effects of glyphosate. This was related to the occurrence (or not) of previous stress situations from exposure to glyphosate. The toxic effect of this herbicide was also evaluated by genetic analysis of insects.
Zavala stated that all animals have the ability to reduce the impact of certain toxic substances that food contains. “For example, these mechanisms allow us to detoxify the caffeine in coffee. We can detect when they are working by looking at the 'activity' of certain genes. Insects also have these genes, which help them to reduce the toxicity of insecticides ”.
Jorge added that until a while ago it was believed that glyphosate only affected plants, but that in their research they looked at the genes of bees to confirm that it was toxic to them. "We were able to detect negative effects even though we used lower doses of glyphosate, even, than those we found in the hives in the field."
The future of bees
“From research similar to ours we know that bees exposed to glyphosate can have a difficult time perceiving the sweetness of a nectar and also learning the relationship between a floral scent and reward. This aggravates the situation of pollinators, since the native flora in agroecosystems is impoverished and more and more efforts must be made to find it, "said Farina.
In addition, to conclude, Farina indicated that hives suffer more complex negative impacts than those found in their laboratory studies, since there is greater complexity in the fields. “More than one agrochemical is applied and the hives suffer many other stresses that produce different responses in the bees. For this reason, in the future we will continue and deepen these joint investigations in productive batches ”.