Residue and dissipation dynamic of spinetoram insecticide in pear fruits

Cacopsylla pyri (Linnaeus, 1758) is the most significant and widespread pear pest. It attacks the pear only, causing direct and indirect damages. This study was conducted in order to evaluate the efficacy of insecticide spinetoram in the control of C. pyri. The experiment was set up according to EPPO methods, at the locality Kula (Republic of Serbia) in a pear orchard (Williams variety). Spinetoram (250 g/kg a.i., WG) was foliar applied in the amount of 0.3 kg/ha, during overlapping pest generations, when pear was on BBCH 75 scale. The efficacy was evaluated through the number of larvae aged L₁–L₃ and L₄–L₅. Spinetoram has shown satisfying efficacy, especially in the control of L₁–L₃ larvae (81.6%). In a dissipation study, spinetoram residues in pear fruits were determined using QuEChERS method followed by HPLC-DAD. The method was validated to fulfill SANTE/12682/2019 criteria. Three days after the application, spinetoram residues in pear fruits were below the MRL (0.2 mg/kg). The results have shown that spinetoram dissipation pattern followed the first-order kinetics (R²= 0.979) with a half-life of 2.17 days, in pear fruits. This study suggests that spinetoram could be safely used in pear, and it could take an important place in insecticide resistance management.

The Study of the Kinetics of Metalaxyl Accumulation and Dissipation in Durian (Durio zibethinus L.) Leaf Using High-Performance Liquid Chromatography (HPLC) Technique

Metalaxyl is an effective approach to control Phytophthora palmivora infection in durian plantation. However, inappropriate metalaxyl usage may increase production cost, pathogen with fungicide resistance, and environmental toxicity. This study established and validated a simple and reproducible procedure to measure metalaxyl concentration in the durian leaf using HPLC. Linearity of the detection ranged from 1–100 µg/mL. The limits of detection (LOD) and quantification (LOQ) were 0.27 and 0.91 µg/mL, respectively. The extraction method gave recovery rates ranging from 88% to 103%. Durian seedlings were treated with 4 g/L metalaxyl either by foliar spray or soil drench. The highest metalaxyl accumulation in durian leaf was found between 6–24 h after treatment and persisted above its effective concentration at least 60 days after foliar application. The dissipation pattern fit to a first-order kinetics equation showed a half-life of 16.50 days. Soil drenching led to eight times higher metalaxyl concentrations in plants than foliar spraying and caused plant death within 15 days after application. These results suggest that foliar spraying of 4 g/L metalaxyl or soil drenching at a lower concentration every two months is sufficient in controlling P. palmivora infection in durian seedlings.

Effect on human health by residues of commonly used pesticides in vegetables cultivation

People in Bangladesh are over scared for toxicity of vegetables & fruits because of the educational level of the farmers is not up to the mark, farmers apply pesticides randomly on agricultural fields without maintaining pre-harvest intervals and dose. The aim of this work was to study dissipation pattern of some pesticides in some vegetables kept at room temperature which represent market condition and to identify and quantify pesticides applied on some vegetables. By interviewing the farmers three commonly used pesticides; cypermethrin, chlorpyrifos and fenvalerate were sprayed in the farmer’s fields of the western part of Bangladesh. Samples were extracted by QuEChERS method, cleaned-up by adsorption chromatography technique, and analyzed by GC-ECD. Recoveries were found to be between 87-107% with RSD lower than 10% at three spiking levels. Matrix matched calibration curves were linear for all the analytes with r2 ≥ 0.99. LODs were found to be 0.01 mg/kg for cypermethrin and 0.002 mg/kg for both of fenvalerate and chlorpyrifos. The samples of same cultivar’s variety were purchased from the markets of Savar, Mymemsingh and Cumilla. Our finding showed only the presence of cypermethrin in tomato but the values were below MRL and no pesticide residue was found in eggplant.

Persistence and dissipation behavior of pesticide residues in parsley (Petroselinum crispum) under field conditions

The residue level, dissipation behavior, and dietary intake risk of chlorpyrifos-methyl, dimethoate, permethrin, iprodione, metalaxyl, and propargite in parsley (Petroselinum crispum) were investigated under field conditions. Extraction and determination of pesticide residues were carried out by a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method and a gas chromatography/tandem mass spectrometry (GC/MS/MS) system, respec-tively. Dissipation of chlorpyrifos-methyl, dimethoate, permethrin, iprodione, metalaxyl, and propargite in pars-ley followed the first-order kinetics with a half-life (t1/2) of 3.33, 3.30, 2.94, 3.52, 4.10, and 3.38 days, respectively. Based on the dissipation pattern and the maximum residue limits (MRL), preharvest intervals (PHI) of 25, 13, 18, 24, 1, and 16 days are suggested for chlorpyrifos-methyl, dimethoate, permethrin, iprodione, metalaxyl, and propargite in parsley, respectively. The estimated daily intake (EDI) of pesticides ranged from 7.37E-05 (dimeth-oate) to 8.00E-04 (metalaxyl) mg/kg. The chronic risk assessment showed that the hazard quotient (HQ) was <1 and Hazard Index (HI, indicating the cumulative exposure to pesticide residues) was <100%, demonstrating that an intake of pesticide residues from parsley was safe for humans.