The sexual reproduction of the nontarget planarian Girardia tigrina is affected by ecologically relevant concentrations of difenoconazole: new sensitive tools in ecotoxicology.

The fungicide difenoconazole, widely used to reduce the negative impacts of fungi diseases on areas with intensive farming, can reach freshwater systems causing deleterious effects on nontarget organisms. The acute and chronic toxicity of a commercial formulation containing 250 g L-1 of difenoconazole (Prisma®) as the active ingredient was assessed in the freshwater planarian Girardia tigrina. The endpoints evaluated were feeding rate, locomotion, regeneration, and sexual reproduction of planarians. The estimated 48 h LC50 of the commercial formulation on planarians expressed as the concentration of the active ingredient difenoconazole was 47.5 mg a.i.L-1. A significant decrease of locomotion (LOEC = 18.56 mg a.i.L-1), delayed regeneration (LOEC = 9.28 mg a.i.L-1), and sexual reproduction impairment, i.e., decreased fecundity and fertility rates (LOEC ≤ 1.16 mg a.i.L-1) were observed on planarians exposed to sublethal concentrations of the formulation. This study demonstrated the importance of using reproductive, physiological, and behavioral parameters as more sensitive and complementary tools to assess the deleterious effects induced by a commercial formulation of difenoconazole on a nontarget freshwater organism. The added value and importance of our research work, namely, the impairment of sexual reproduction of planarians, contributes to the development of useful tools for ecotoxicology and highlights the fact that those tools should be developed as guidelines for testing of chemicals. Our results showed that the use of reproductive parameters of Girardia tigrina would help to complement and achieve a better assessment of the risk posed by triazole fungicides to freshwater ecosystems.

Comparative Performance of Fungicides and Biocontrol Products in the Management of Fusarium Wilt of Blackberry.

Fusarium wilt of blackberry (FWB) is an emerging disease caused by a Fusarium oxysporum species complex. More than 3,000 ha of blackberry (Rubus spp.) crops have been lost in Mexico since 2011. The objectives of this research were: to evaluate the sensitivity of pathogenic F. oxysporum isolates recovered from symptomatic blackberry plants to fungicides with different modes of action; to assess the potential of these fungicides and plant resistance inducers against FWB in the greenhouse; and to determine the effects of commercial biofungicides and two indigenous strains of Trichoderma spp. on the incidence of FWB. The EC50 values of the fungicides prochloraz, thiabendazole, azoxystrobin, thiophanate-methyl, difenoconazole, triflumizole, and potassium phosphite for six pathogenic F. oxysporum isolates were determined. In a separate experiment, the fungicides acibenzolar-s-methyl (ASM), potassium phosphite, and commercial biofungicides, as well as two soil microbial inoculants and two indigenous Trichoderma strains, were tested for protection against wilt development in blackberry plants in the greenhouse. Prochloraz showed an average sensitivity for EC50 of 0.01 µg ml-1 for the tested F. oxysporum isolates, followed by difenoconazole and thiabendazole. Prochloraz and ASM proved to be the most effective treatments in the greenhouse. In contrast, potassium phosphite was ineffective in both the in vitro and in vivo experiments. The soil bioinoculants MicroSoil, Baktillis, T. koningiopsis, and T. asperellum significantly reduced the incidence of disease in the greenhouse. These results provide evidence for the potential of the various tools as useful components of integrated FWB management in the field.

Endpoints as human biomarkers in exposure assessment of triazoles fungicides.

Potential endpoint biomarkers were evaluated in the assessment of exposure to triazoles, in the southern region of Minas Gerais, Brazil. Volunteers were divided into three groups: occupationally exposed and rural residents (n = 21), non-occupationally exposed and rural residents (n = 35) and non-occupationally exposed and urban residents (n = 30). Of all endpoints evaluated, plasma concentration of androstenedione (p < 0.001) and glycine-conjugated bile acids presented statistical differences in the three studied groups (p < 0.05). However, our findings concerning oxidative stress and testosterone levels, plus that related to unconjugated and taurine conjugated bile acids, suggested that more studies are necessary to evaluate their potential as biomarkers for triazole exposure, as statistical significance was not attained between the groups. Our human population data contributes to the development of triazole exposure risk assessment with respect to these potential effect biomarkers, in potentially vulnerable groups and individuals.

Lethal and sub-lethal effects of cyproconazole on freshwater organisms: a case study with Chironomus riparius and Dugesia tigrina.

The fungicide cyproconazole (CPZ) inhibits the biosynthesis of ergosterol, an essential sterol component in fungal cell membrane and can also affect non-target organisms by its inhibitory effects on P450 monooxygenases. The predicted environmental concentration of CPZ is up to 49.05 µg/L and 145.89 µg/kg in surface waters and sediments, respectively, and information about CPZ toxicity towards non-target aquatic organisms is still limited. This study aimed to address the lack of ecotoxicological data for CPZ, and thus, an evaluation of the lethal and sub-lethal effects of CPZ was performed using two freshwater invertebrates (the midge Chironomus riparius and the planarian Dugesia tigrina). The estimated CPZ 48 h LC50 (95% CI) was 17.46 mg/L for C. riparius and 47.38 mg/L for D. tigrina. The emergence time (EmT50) of C. riparius was delayed by CPZ exposure from 0.76 mg/L. On the other hand, planarians showed higher tolerance to CPZ exposure. Sub-lethal effects of CPZ on planarians included reductions in locomotion (1.8 mg/L), delayed photoreceptors regeneration (from 0.45 mg/L), and feeding inhibition (5.6 mg/L). Our results confirm the moderate toxicity of CPZ towards aquatic invertebrates but sub-lethal effects observed also suggest potential chronic effects of CPZ with consequences for population dynamics.