Talyta Zortéa

Soil fauna and its relation with environmental variables in soil management systems

The present study aims to generate knowledge about the soil fauna, its relation to other explanatory environmental variables, and, besides it, to select edaphic indicators that more contribute to separate the land use systems (LUS). Five different LUS were chosen: conventional tillage with crop rotation (CTCR); no-tillage with crop rotation (NTCR); conventional tillage with crop succession (CTCS); no-tillage with crop succession (NTCS) and minimum tillage with crop succession (MTCS). The samples were made in the counties Chapeco, Xanxere and Ouro Verde located in the state of Santa Catarina, Brazil, and were considered the true replicates of the LUS. In each site, nine points were sampled in a sampling grid of 3 x 3. At the same points, soil was sampled for the physical, chemical and biological attributes (environmental variables). Pitfall traps were used to evaluate the soil fauna. Data were analyzed using principal component analysis (PCA) and canonical discriminant analysis (CDA). The soil fauna presented potential to be used as indictors of soil quality, since some groups proved to be sensible to changes of the environmental variables and to soil management and tillage. The soil management using crop rotation (NTCR and CTCR) presented higher diversity, compared to the systems using crop succession (NTCS, MTCS and NTCS), evidencing the importance of the soil tillage, independent of the season (summer or winter). The variable that better contributed to explain these changes were the chemical variables (potassium, pH, calcium, organic matter, available phosphorus, potential acidity), and biological variables (Shannon diversity index, Collembola, Pielou equitability index and microbial biomass carbon), respectively.

Influence of cypermethrin on avoidance behavior, survival and reproduction of Folsomia candida in soil.

Cypermethrin is a pyrethroid widely used in agriculture and in control of animal ectoparasites, being effective against a large number of insects. Therefore, this study aimed to evaluate the effects of cypermethrin on soil fauna using reproduction and behavior ecotoxicological tests with the springtail Folsomia candida. The surface layer of a soil characteristic of the western region of the Santa Catarina State, classified as Typic Dystrupept, was used as test substrate. The treatments on both tests consisted of five concentrations of cypermethrin (0, 7.5, 15.0, 22.5, and 30.0mgkg(-)(1)) corresponding to 0, 1.5, 3.0, 4.5, and 6.0gm(-2), respectively. This range was chosen according to technical instruction for the use of this product in broilers beds (that are used afterwards as organic fertilizer in soil) that recommends 15mgkg(-1) (3.0gm(-2)). The results obtained with tests for F. candida showed toxicity at all doses tested, following a dose-related response resulting in reduction in survival rate (LC50 of 18.41mgkg(-1), equivalent to 3.8gm(-2)), in the number of juveniles (EC50 of 15.05mgkg(-1), corresponding to 3.01gm(-2)), and an increase in avoidance response (AC50 of 29mgkg(-1), corresponding to 5.8gm(-2)). Although more studies are needed focusing on the fate of cypermethrin in soil when the poultry beds are used as fertilizer and how it may affect soil fauna, data obtained in this study, by showing effects within the range of the doses that are recommended implies that caution and possible mitigation measures should be taken when using this compound.

Melaleuca alternifolia Essential Oil against the Lesser Mealworm (Alphitobius diaperinus) and Its Possible Effect on the Soil Fauna

The aim of this study was to evaluate the in vitro bioactivity of tea tree (Melaleuca alternifolia) essential oil against larvae and adult forms of lesser mealworms (Alphitobius diaperinus) and its influence on the soil fauna. Tests were performed in triplicate using pure tea tree oil (TTO; 1, 5, 10, 25, 50, and 100%), TTO nanoparticles (1, 3, and 7.5%), or terpinen-4-ol, the main compound of the tea tree oil, at the same concentrations of TTO. Larvae and adult mortality occurred at concentrations up to 10 and 50% of TTO, respectively. No larvicidal or insecticidal effect of TTO nanoparticles was observed. Terpinen-4-ol showed insecticidal and larvicidal effect at concentrations higher than 25%. The evaluation of TTO effect on soil organisms was performed by standard ecotoxicological tests (ISO) with the springtail species Folsomia candida. Only TTO was used for ecotoxicological tests in doses of 1, 5, 10, 25, 50, and 100 mg kg-1 of soil. TTO had no negative effects on F. candida survival or reproduction. Therefore, it was concluded that M. alternifolia oil may be a new alternative for control of the lesser mealworm.

Ecotoxicological effect of fipronil and its metabolites on Folsomia candida in tropical soils

The aim of this study is to evaluate the toxicity of the fipronil and its metabolites, fipronil sulfone and fipronil desulfinyl on Folsomia candida. Three types of soils were used to perform the ecotoxicological tests, two natural soils (Oxisol and Entisol), and an artificial substrate (Tropical Artificial Soil). The treatments consisted of increasing doses of a veterinary medicinal product with active ingredient based on fipronil, and of its two main metabolites, fipronil sulfone and fipronil desulfinyl. The doses of fipronil were 0.00, 0.02, 0.04, 0.08, 0.15, 0.30, 0.60, and 1.00 mg kg-1 of the active ingredient. For fipronil sulfone and fipronil desulfinyl the doses tested were: 0.00, 0.01, 0.02, 0.04, 0.06, 0.08, 0.15, 0.30, 0.60, 1.00, and 5.00 mg kg-1. The effects of toxicity on F. candida were evaluated by survival and reproduction tests, based on the methods described by ISO 11267. There was a completely randomized design, with six replicates for the fipronil tests and eight for the metabolites. We show that fipronil and its metabolites, even at very low concentrations, are toxic to F. candida. Reduction of reproduction can be observed at concentrations of 0.15 mg kg-1. There was little difference in toxicity (LC50 and EC50) between fipronil and its metabolites. Rather, differences were related more to soil type, where the artificial soil was more sensitive than the two natural soils (Oxisol and Entisol). We conclude that it is important to perform ecotoxicological tests in natural soils, in order to generate more realistic representations of veterinary drug toxicity on the environment.

Ecotoxicological effects of fipronil, neem cake and neem extract in edaphic organisms from tropical soil

Veterinary medicines are widely applied for the treatment and prevention of animal diseases. Consequently, animal manure contains significant amounts of environmental pollutants that are potential sources of environmental pollution when inappropriately applied in soils. This work aimed to evaluate ecotoxicological effects of doses of commercial fipronil, neem cake and neem extract in the survival and reproduction of earthworms (Eisenia andrei), enchytraeidae (Enchytraeus crypticus) and springtails (Folsomia candida) in Oxisol and tropical artificial soil (TAS). Applications of fipronil, neem cake and extract in soil were carried out according to standardized ISO methodologies by using a random experimental design with five replicates. Toxic effects of fipronil for springtails in Oxisol and TAS were observed with LC50 of 0.26 mg kg-1 (0.18-0.35 mg kg-1) and 0.29 mg kg-1 (0.22-0.37 mg kg-1), respectively. It was not observed significant toxic effects of fipronil for earthworms and enchytraeidae in both soils. However, significant amounts of juvenile earthworm and adult enchytraeidae decreased in fipronil doses higher than 10 mg kg-1. Neem cake and extract were not toxic for earthworms and enchytraeidae but, significant amounts of juvenile springtails decreased in neem cake doses from 500 to 1000 mg kg-1. It can be concluded that the use of veterinary medicines containing synthetic compounds for preventing diseases in animals needs to be controlled to avoid environmental pollution after applying manure in soil. Veterinary medicines containing natural compounds as neem cake and extract are eco-friendly and could be efficiently applied in soil in a sustainable way.

Insecticidal Action of Glycerol Monolaurate against the Lesser Mealworm (Alphitobius diaperinus) and its Ecotoxicological Effect on Enchytraeus crypticus

Background: Alphitobius diaperinus, known as the lesser mealworm, is recognized as a problem for the poultry production sector. Several chemical methods have been employed in an attempt to control it, without successful results. Thus, alternative methods should be considered as an interesting approach to control this type of infestation. A recent study showed that glycerol monolaurate (GML) possesses insecticidal effect against bees. Therefore, the aim of this study was to evaluate, for the first time, the effect of GLM against the larval and adult forms of the lesser mealworm in vitro, and to verify whether GLM treated poultry litter used as soil fertilizer exerts any negative effect on its fauna. Materials, Methods & Results: In vitro tests were performed using three concentrations of GLM: 0.2, 0.4 and 1 mg mL-1, and the number of dead larvae and adults of A. diaperinus was counted on days 0, 2, 5 and 8 post-treatment. Poultry litter was pulverized with 1 mg mL-1 of GML, maintained under controlled conditions for 20 days and revolved every two days. Two ecotoxicological tests were performed using Enchytraeus crypticus. In the first test, GML was applied directly into the soil at doses of 0.5, 1 and 2 mg kg-1 of soil, while the second test used poultry litter as soil fertilizer at concentrations of 0, 2, 4 and 8 tons per hectare. Insecticidal action of GML against larvae and adults of A. diaperinus where only the 1 mg mL-1 concentration showed positive effect. GML caused 100% mortality of larvae two days after the beginning of treatment. Similarly, GML showed high efficacy to control adult forms of A. diaperinus, causing 83 and 90% of mortality on days 5 and 8 post-treatment, respectively. No difference was observed while applying GML directly at doses of 0.5, 1 and 2 mg kg-1 in the TAS when compared to the control group, similarly to what was observed using poultry litter containing 1 mg/m2 of GML at concentrations of 0, 2, 4 and 8 tons per hectare compared to the control group. Discussion: GML treatment exerted larvicidal and insecticidal action in vitro against A. diaperinus, similarly to what was observed by researchers against bees, where this product was able to eliminate 55% of the bees after 120 h of treatment. GML insecticidal mechanism of action is poorly investigated and remains unknown. However, there are evidences regarding its antimicrobial property using Staphylococcus aureus, Streptococcus spp., Enterococcus faecalis, as well as its capacity to inhibit some virulence factors linked to antimicrobial resistance. Some tests have been performed in order to reduce the use of chemical products, as Melaleuca alternifolia (tea tree oil), Ocotea odorifera (popularly known as sassafras) and Eucalyptus viminalis (popularly known as eucalypt) essential oils exerts insecticidal action against the larvae and adults of mealworms. The main chemical used to control A. diaperinus is cypermethrin, a chemical product that can damage the soil fauna due to its intensive utilization. The use of GML did not cause negative effects in the soil fauna, in disagreement other study with GML at concentrations of 50 and 100 µg mL-1 and found negative effects on the soil fauna using adults and juvenile forms of springtails (Folsomia candida) as biomarkers, showing a LD50 of 41 µg mL-1. Based on these evidences, we can suggest that the toxicity of GML to soil fauna is related to the biomarker used to determine the toxicity. Therefore, it is possible to conclude that GML possesses insecticidal action without toxic effects for the soil fauna, demonstrating potential as an alternative method to control the lesser mealworm.

AVALIAÇÃO DA TOXICIDADE DO COBRE EM DOIS SOLOS NATURAIS COM DIFERENTES FAIXAS DE pH – Uma abordagem com plantas e organismos edáficos

O objetivo do trabalho e avaliar os efeitos da calagem na toxicidade do cobre, sobre a germinacao de plantas e na biota do solo. Foram realizados testes ecotoxicologicos de germinacao de sementes, nos quais foram utilizadas as especies Avena sativa e Vicia villosa , bem como teste de fuga com organismos testes da especie Enchytraeus crypticus. Os tratamentos consistiram em doses crescentes (0; 10, 40, 80, 160 e 320 mg kg -1 ) de sulfato de cobre (CuSO 4 ), em Latossolo e Neossolo com pH corrigido e nao corrigido. A exposicao de sementes de A. sativa e V. villosa a doses crescentes de CuSO 4 nao expressou efeito toxico na taxa de germinacao (P>0,05), independente da correcao do pH. Foi observado fuga significativa para o Latossolo ja na primeira dose avaliada, enquanto no Neossolo tambem houve fuga significativa, porem, com variacao das doses de acordo com a correcao do pH. Deste modo, a contaminacao de diferentes tipos de solos naturais com CuSO 4 nao afeta a taxa de germinacao das sementes, mas apresenta alta toxicidade para enquitreideos E. crypticus .