Plant-Parasitic Nematodes (Nematoda: Tylenchomorpha) Associated with Different Crops in the Damavand Region, with Descriptions of Two New Records for Iran

Document Type : Research Paper

Authors

• Vahideh Mahdavi ¹
• Fatemeh Khelghatibana ²
• Ali Es-haghi ³
• Kasra Sharifi ⁴
• Mahdieh Hoseini ⁵
• Hosein Parsa ⁶
• Hooman Nankali ⁷

¹ Department of Pesticides Research, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

² 2. Department of Plant Diseases Research, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

³ 3. Department of Physical Chemistry, Razi Vaccine and Serum Research Institute, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

⁴ 4. Department of Plant Diseases Research, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

⁵ 5. Department of Pesticides Research, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

⁶ 6. Department of Pesticides Research, Iranian Research Institute of Plant Protection, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

⁷ 7. Qazvin Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Tehran, Iran

Abstract

Keywords

• Fungicide
• Kinetic
• Residue
• Pre-harvest interval

Extended Abstract

Introduction

Objective

     Today, there is an urgent need to investigate the rate of pesticides reduction and degradation in field settings and to assess safe pre-harvest intervals to ensure that pesticide residues in the crop remain within regulatory limits (safe). In this study, the residues and dissipation kinetics of difenoconazole + fluxapyroxad as Dagonis^® (SC 7.5/5) used to control powdery mildew on tomatoes, as well as the fungicides dimethomorph + cymoxanil as Pilarexanil^® (WG 70%) used to control internal powdery mildew on cucumbers, were investigated. The pre-harvest interval (PHI) for these pesticides in cucumber and tomato crops was estimated to be 3 days, derived from kinetic analyses of degradation and reduction under greenhouse conditions at optimum and maximum application rates.

Materials and Methods

 In this study, Certified Reference Materials (CRMs), acetonitrile and Poly Secondary Amin (PSA) were obtained from Sigma-Aldrich, Scharlau (Barcelona, Spain) and Agilent Technologies (USA), respectively. The pre-harvest interval (PHI) was evaluated at the optimal doses of the studied pesticides. Alverd^@ 240 SC insecticide at 1000 mL/ha and Proclaim Fit^@ UV 500 WG insecticide at 100 g/ha demonstrated the best efficiency. Consequently, residue analyses in tomato crops and the evaluation of the proposed PHI were conducted at these doses. A quick, easy, cheap, effective, rugged, and safe (QuEChERS)-based sample preparation method was employed. Pesticide analyses in cucumber and tomato samples were performed using liquid chromatography-tandem mass spectrometry (LC-MS/MS) Pesticide analyses in cucumber and tomato samples were performed. The separation was performed on a Zorbax Eclipse SB-C₁₈ column (3.0 × 50.0 mm, 1.8 µm) using a mobile phase of acetonitrile and water containing 0.1% formic acid. The gradient program started at 10% acetonitrile, increasing linearly to 100% by 13 minutes, and returned to the initial conditions by 20 minutes, at a flow rate of 0.4 mL/min. The optimum MS conditions were determined with respect to fragmentation voltage and the collision energies of each pesticide. The standard solutions of each pesticide (1 mg kg^-1) were separately prepared in acetonitrile and injected directly into the MS using a single-syringe infusion pump. 

Results and discussion

     The method underwent validation, revealing a linear dynamic range (LDR) for matrix-matched calibration curves of 0.01–0.5 mg/kg, with coefficients of determination (R²) exceeding 0.99. The limits of detection (LOD) and quantification (LOQ) were 0.003–0.005 mg/kg and 0.01 mg kg^-1, respectively. Accuracy and precision were evaluated at two concentration levels. Recoveries ranged from 75.2 to106.3%, with relative standard deviations (RSD%) for triplicate analyses below 14.2% for all analytes. The developed method was applied to tomato and cucumber samples collected from Alborz and Ghazvin province, and four pesticide residues were found at concentrations below their maximum residue limits (MRLs). Based on the residue results for difenoconazole and fluxapyroxad in tomatoes samples treated with these pesticides, the 3-day pre-harvest interval (PHIs) of Dagonis^® and the 3-day pre-harvest interval of Pilarexanile^®, dimethomorph and cymoxanile in cucumber samples were investigated and confirmed.

Conclusions

     In this study, the kinetics of degradation and reduction of difenoconazole plus fluxapyroxad as a SC 7.5/5 (Dagonis^®) for controlling powdery mildew on tomatoes, and fungicides dimethomorph plus cymoxanil as a WG 70% (Pilarexanil^®) for controling internal powdery mildew on cucumbers, were investigated. The pre-harvest interval (PHI) for these pesticides in cucumber and tomato crops was estimated at 3 days. This interval was derived from the observed kinetics of degradation and reduction at optimum and maximum application rates in greenhouse cucumber and tomato crops. Residual monitoring was conducted immediately after spraying and continued for 11 days, with three replicates. Residue levels were assessed against national maximum residue limits (MRLs), and for all compounds, residues remained below the national MRLs at all sampling times. Consequently, the 3-day PHI for both Dagonis^® and Pilarexanil^® is deemed acceptable. The first-order kinetic models fitted to the pesticides studied also confirm the 3-day PHI.

Based on the results, the following recommendations are presented:

• Use of registered pesticides
• Use of pesticides at an appropriate time
• Use of pesticides in appropriate doses and concentrations, with recommended spraying intervals
• Use of appropriate spraying methods (appropriate to the type of pesticide, target pest, host and production space)
• Avoid the use of unauthorized, counterfeit, unknown, suspicious, and poorly qualified pesticides
• Compliance with the expiration date of pesticides and paying attention to the warnings on pesticide labels
• More practical supervision for the import, production, and packaging of agricultural pesticides

Author Contributions

Vahideh Mahdavi: Resources, Funding acquisition, Validation, Visualization, Supervision, Writing-original draft; Fatemeh Khelghatibana: Conceptualization, Sample treatment, planning, Investigation; Ali Es-haghi: Formal analysis, Data curation, Methodology, Kasra Sharifi: Conceptualization, Sample treatment, planning, Investigation; Mahdieh Hoseini: Software, Formal analysis, Data curation, Methodology; Hosein Parsa: Extraction and Writing-original draft; Hooman Nankali: Supervision for real samples, Sampling. All authors have read and approved the published version of the manuscript.

Data availability statement

Data will be available upon request.

Acknowledgements

The authors greatly thank the Iranian Research Institute of Plant Protection (IRIPP) to provide the necessary facilities and equipment. 

Ethical considerations

Not applicable.

Conflict of interest

The authors declare that they have no conflict of interest.