Enzymatic effects of pesticides on Apis mellifera colonies placed in a pulverized soybean field

MICHLIG, MELINA P.; BRASCA, ROMINA; DEMONTE, LUISINA D.; MAGNI, FLORENCIA V.; RAATS, DAIANA; BLETTER, DIEGO; ATTADEMO, ANDRÉS M.; REPETTI, MARÍA ROSA

Panamá

Workshop; 9TH Latin American Pesticide Residue Workshop (LAPRW); 2023

Ministerio de Desarrollo Agropecuario de Panamá (MIDA)

The increasing loss of pollinators is a worldwide concern, because it affects not only the maintenance of natural ecosystems, but also crop production. The close relationship that bees have with agricultural areas leaves them exposed to a significant load of agrochemicals in those environments. Forager bees can come into contact with different agrochemicals on their collection trips by flying through polluted particle clouds, by contacting treated plants or near a treated crop, or by collecting water, nectar, or pollen with pesticide residues. The objective of this study was to determine the effect of pesticides of common use on soybean crops on A. Mellifera under real field conditions. For that, three hives were placed on a 10 hectares lot of soybean during the blooming season. Ten days after placing the hives, lambda-cyhalothrin, methoxyfenozide and glyphosate were sprayed. The sampling of the three hives was carried out in three periods regarding the pulverization 48 and 1 hour before the pulverization (pre-pulverization), immediately after pulverization (during pulverization), and 48 and 96 h after pulverization (post-pulverization). The bees were subjected to pesticide residue analysis and their enzymatic (AChE; Acetylcholinesterase, CbE; Carboxylesterase and GST; Glutathione S-transferase) activities were determined. The results showed that lambda-cyhalothrin residues in the bee bodies did not vary between the different sampling days. In fact, 73 percent of samples were not detected and the positives were lower than the limit of quantification of 4 µg kg-1. Among the remaining pesticides under study, methoxyfenozide residues were detected in the bee samples taken during pulverization, where the maximum concentration was of 50 µg kg-1 of bee. Both glyphosate and its principal metabolite, AMPA, were detected in most bee bodies (87 % and 100 % of samples were positive for glyphosate and AMPA, respectively). Pulverization had a significant impact on enzymatic activity, both AChE and GST activity were reduced in the post-pulverization samples. Instead, CbE activity increased 250 and 166 % during and after pulverization, respectively. The increased activity of CbE observed immediately after and post-pulverization suggests this key metabolic detoxification enzyme contributes to bee tolerance to the applied pesticides. Overall, this study has shown not only the complex pollutant load that bees may be subjected to in a typical agroecosystem, but also how it affects key biochemical parameters. In this sense, the levels of enzymatic activities of AChE, CbE and GST resulted in useful biomarkers to evaluate bee exposure to the compounds, and to understand the effects they can have on the physiology and ecological performance of these essential pollinators.