RESUMO
Currently, only Apis mellifera is used in environmental regulation to evaluate the hazard of pesticides to pollinators. The low representativeness of pollinators and bee diversity in this approach may result in insufficient protection for the wild species. This scenario is intensified in tropical environments, where little is known about the effects of pesticides on solitary bees. We aimed to calculate the medium lethal dose (LD50) and medium lethal concentration (LC50) of the insecticide dimethoate in the Neotropical solitary bee Centris analis, a cavity-nesting, oil-collecting bee distributed from Brazil to Mexico. Males and females of C. analis were exposed orally to dimethoate for 48 h under laboratory conditions. Lethality was assessed every 24 h until 144 h after the beginning of the test. After the LD50 calculation, we compared the value with available LD50 values in the literature of other bee species using the species sensitivity distribution curve. In 48 h of exposure, males showed an LD50 value 1.33 times lower than females (32.78 and 43.84 ng active ingredient/bee, respectively). Centris analis was more sensitive to dimethoate than the model species A. mellifera and the solitary bee from temperate zones, Osmia lignaria. However, on a body weight basis, C. analis and A. mellifera had similar LD50 values. Ours is the first study that calculated an LD50 for a Neotropical solitary bee. Besides, the results are of crucial importance for a better understanding of the effects of pesticides on the tropical bee fauna and will help to improve the risk assessment of pesticides to bees under tropical conditions, giving attention to wild species, which are commonly neglected. Environ Toxicol Chem 2023;42:2758-2767. © 2023 SETAC.
Assuntos
Himenópteros , Inseticidas , Praguicidas , Feminino , Abelhas , Animais , Inseticidas/toxicidade , Praguicidas/toxicidade , Dimetoato/toxicidade , Medição de RiscoRESUMO
All across the world, different countries use Ecological risk assessments (ERA) of pesticides to pollinators as a regulatory tool to understand the safety of pesticide use in agriculture. However, pesticide application is still recognized as one of the main stress factors causing a decline in the global population of bees. In all ERA procedures, the effects of pesticides on the honey bee species Apis mellifera are used as a reference for the effects on all different bee species. To evaluate if tropical native bees are protected by the current risk assessment procedures and to propose improvements to the methods, we assessed the ecological risk of the neonicotinoid imidacloprid posed to native and exotic bee species. The risk was assessed through a low (TIER I) and an intermediate (TIER II) level of analysis. For TIER I the USEPA BeeREX model was used and for TIER II the Species Sensitivity Distribution (SSD) approach was adopted. For the imidacloprid exposure conditions, four different crops were taken into consideration; bean, passion fruit, sunflower and tomato. The imidacloprid risk on native species was assessed both by extrapolating the effects obtained to Apis species, and by using ecotoxicological data from tests performed with native species. In TIER I, the risks calculated through empirical data showed that more than 50% of the non-Apis species presented risk levels of 28-180% higher than those obtained with the extrapolation factor used in the Brazilian pesticide regulation. In TIER II, the SSDs showed that most of the native bees are more sensitive to imidacloprid than the Africanized A. mellifera. This is the first study in which an ERA of a pesticide was conducted on tropical bee species. Here we also present some gaps and perspectives for future studies aiming to improve the risk assessment of pesticides in terrestrial environments.
Assuntos
Inseticidas , Praguicidas , Animais , Abelhas , Brasil , Inseticidas/análise , Inseticidas/toxicidade , Neonicotinoides/toxicidade , Nitrocompostos/toxicidade , Praguicidas/análiseRESUMO
Essential to the provision of important ecosystems services, i.e., food production, soil is suffering great pressure. The degradation of natural areas in order to turn them into croplands has been causing severe effects to the soil quality, including the maintenance of their biodiversity. Soil physical disruption reduce the soil biodiversity and, consequently, may cause negative effects to the supporting services, i.e., organic matter degradation and nutrient cycling, which will directly or indirectly impact agroecosystems. In this study, the influence of three different types of land uses (native forest (NF), conventional agriculture (CA), and organic agriculture (OA)) to the soil mesofauna (emphasizing collembolan and mites) were assessed under real scenarios in the southeast part of Brazil. Both conventional and organic fields were of strawberries, and the greatest difference in their processes was the use of synthetic fertilizers and pesticides, performed at CA. Soil fauna organisms were collected and identified to main groups, except the collembolan species which were further separated into four main groups/family. Results showed that not only the physical changes due to soil tillage caused negative effects to soil fauna. In the field where the use of agricultural products was allowed, organisms were much more severely affected. Hence, the conversion of natural forested areas to agricultural lands may harm soil fauna communities through biodiversity loss. This study not only adds significant information to the knowledge regarding the relation between biodiversity loss and agricultural practices worldwide, but it also helps to improve Brazilian knowledge of the edaphic fauna in agroecosystems.