Dissipation kinetics and safety evaluation of tebuconazole and trifloxystrobin in tea under tropical field conditions

Integrated Transcriptome and Proteome Analysis Reveals that the Antimicrobial Griseofulvin Targets Didymella segeticola Beta-Tubulin to Control Tea Leaf Spot

Because effective control measures are lacking, tea leaf spot caused by Didymella segeticola results in huge tea (Camellia sinensis) production losses on tea plantations in Guizhou Province, southwestern China. Screening for natural antimicrobial agents with higher control effects against this pathogen and studying their modes of action may contribute to disease management. Here, Penicillium griseofulvum-derived antimicrobial griseofulvin (GSF) can inhibit the hyphal growth of D. segeticola strain GZSQ-4, with a half-maximal effective concentration of 0.37 μg/ml in vitro and a higher curative efficacy at a lower dose of 25 μg/ml for detached tea twigs. GSF induces deformed and slightly curly hyphae with enlarged ends, with protoplasts agglutinated in the hyphae, and higher numbers of hyphal protuberances. GSF alters hyphal morphology and the subcellular structure's order. The integrated transcriptome and proteome data revealed that the transport of materials in cells, cellular movement, and mitosis were modulated by GSF. Molecular docking indicated that beta-tubulin was the most potent target of GSF, with a binding free energy of -13.59 kcal/mol, and microscale thermophoresis indicated that the dissociation constant (Kd) value of GSF binding to beta-tubulin 1, compared with beta-tubulin 2, was significantly lower. Thus, GSF potentially targets beta-tubulin 1 to disturb the chromosomal separation and fungal mitosis, thereby inhibiting hyphal growth.

Dissipation rate and exposure risk of trifloxystrobin in dry climatic field environments

The investigation of the magnitude of residues after application of a pesticide is important to ensure consumer safety and is also a regulatory requirement to grant authorization. To address those issues, the behavior of trifloxystrobin residues was investigated in outdoor strawberry and cucumber cultivations, following the recommended and more critical agricultural practices under Egyptian dry climatic conditions. Fruits were collected at several pre-harvest intervals and analyzed with the Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) extraction protocol followed by liquid chromatography-tandem mass spectrometry. The limit of quantitation of the method was 0.001 mg kg−1. When trifloxystrobin was applied on the field, the half-lives were 2.4 days in cucumbers and 6.2 days in strawberries. Risk assessment showed that chronic and acute dietary exposure to residues following the investigated agricultural patterns are of no concern to consumers.

Index design and safety evaluation of pesticides application based on a fuzzy AHP model for beverage crops: tea as a case study

BACKGROUND

A fuzzy analytic hierarchy process (AHP) is shown to be an effective methodology for multiple criteria decision-making from various heterogeneous data. Despite application of AHP to some decision-making problems in agriculture, research on AHP utilization for screening the safe use of pesticides for tea plantations based upon multiple criteria has not been reported. The overall safety chain from tea plantation to tea manufacture to tea cup after pesticides had been sprayed on a tea plantation was considered and the AHP network was constructed at two levels with two categories, tea-related parameters and pesticide toxicity. Seven criteria were selected as safety indexes, half-lives of pesticides on the tea plant (T_1/2 ), water solubility (Ws), vapor pressure (Vp), acceptable daily intake (ADI), acute oral lethal dose of pesticides to rat (LD₅₀ ), and ecotoxicity of pesticides including LD₅₀ to bees and LD₅₀ to aquatic organisms.

RESULTS

According to the AHP, water solubility was the most important factor in the evaluation pesticide safety for use on a tea plantation, followed by the half-lives of the pesticides on the tea plant and the acceptable daily intake. Combined with the scale of seven criteria and relative weight (W), 48 pesticides with an overall score (S) < 25 could be regarded as relatively safe compounds when applied in tea plantations.

CONCLUSION

An AHP approach was suggested to evaluate the safe use of pesticides on tea plantations. This study provides a new idea for the evaluation of safety in beverage crops. © 2019 Society of Chemical Industry.

Determination, residue and risk assessment of trifloxystrobin, trifloxystrobin acid and tebuconazole in Chinese rice consumption

A simple and rapid analytical method for the detection of trifloxystrobin, trifloxystrobin acid and tebuconazole in soil, brown rice, paddy plants and rice hulls was established and validated by liquid chromatography with tandem mass spectrometry. Acceptable linearity (R²  > 0.99), accuracy (average recoveries of 74.3-108.5%) and precision (intra- and inter-day relative standard deviations of 0.9-8.8%) were obtained using the developed determination approach. In the field trial, the half-lives of trifloxystrobin and tebuconazole in paddy plants were 5.7-8.3 days in three locations throughout China, and the terminal residue concentrations of trifloxystrobin and tebuconazole were <100 and 500 μg/kg (maximum residue limits set by China), respectively, at harvest, which indicated that, based on the recommended application procedure, trifloxystrobin and tebuconazole are safe for use on rice. The risk assessment results demonstrated that, owing to risk quotient values of both fungicides being <100%, the potential risk of trifloxystrobin and tebuconazole on rice was acceptable for Chinese consumers. These data could provide supporting information for the proper use and safety evaluation of trifloxystrobin and tebuconazole in rice.