Pesticide dissipation curves in peach, pear and tomato crops in Uruguay*

Abstract

Dissipation curves of azoxystrobin and of the neonicotinoids acetamiprid and thiacloprid in peach; azinphos-methyl and carbaryl in pear and azoxystrobin, chlorfenapyr and chlorpyrifos in high-tunnel tomato crops were studied in the Southern region of Uruguay. An analytical methodology based on solid phase extraction (SPE) and detection by High Performance Liquid Chromatography with Diode Array Detector (HPLC/DAD) was used for acetamiprid and thiacloprid. Coupled SPE and detection by Gas Chromatography with Mass Selective Detector (GC/MSD) was used for the detection of azinphos-methyl, azoxystrobin, carbaryl, chlorfenapyr and chlorpyrifos residues. Curves were modeled mathematically with Solver program of Microsoft Excel. The best fit for acetamiprid and thiacloprid in peach was achieved with the exponential model (r(2)=0.961 and 0.944, respectively). In the case of peach fruits there is not a Maximum Residue Limit (MRL) for acetamiprid in the Codex Alimentarius, while 0.5 mg/kg is the value rated for thiacloprid. The MRLs accepted by the European Union (EU) are 0.1 mg/kg for acetamiprid and 0.3 mg/kg for thiacloprid. According to the curves determined in these experiments, thiacloprid residues 10 to 12 days after application (daa) were below the MRLs established by both sources. In the case of acetamiprid, 25 daa would be required, according to the exponential mathematical model, to get residues levels below the MRL values established by the EU. For azinphos methyl in pear, the residues detected were mathematically fitted to an exponential model (r(2)=0.999). According to it, residue levels under the MRL established by the EU (0.05 mg/kg) are gotten in our conditions in 20 daa. In plastic tunnel tomato chlorfenapyr residues were not detected from 16 daa, having the dissipation curve an exponential trend. In the same condition, there was not a decay of the azoxystrobin concentration during a 24-day trial, being it around 0.40 ± 0.05 mg/kg.

Degradation of imazalil, orthophenylphenol and pyrimethanil in Clementine mandarins under conventional postharvest industrial conditions at 4°C

“…However, as the PYR residues were well below the legal MRLs, longer evaluation times were not considered. Similar retention of residues without decline of the fungicide azoxystrobin on fruits stored in cold chambers were reported in tomato (Galietta et al, 2011). Moreover, cross-contamination with PYR has been detected when no appropriate clean up measures are taken.…”

Assessing Field‐Scale Risks of Foliar Insecticide Applications to Monarch Butterfly (Danaus plexippus) Larvae

“…Length of dietary exposure is a function of an insecticide's photolysis, hydrolysis, and oxidation rates. In field and greenhouse studies conducted with growing plants, beta‐cyfluthrin was found to have a half‐life of 1 to 2 d (Banerjee et al 2012), whereas chlorpyrifos, imidacloprid, and thiamethoxam had half‐lives of 2 to 6 d (Galietta et al 2011; Hassanzadeh et al 2012; Rahman et al 2015). Chlorantraniliprole has a reported half‐life of 16 to 17 d (Szpyrka et al 2017).…”

Method validation and dissipation dynamics of chlorfenapyr in squash and okra

“…Chlorfenapyr is a GC amenable pesticide and has been determined using GC equipped with ECD (Ditya et al, 2010;Ou et al, 2006;Rahman et al, 2012) and MSD (Galietta et al, 2011). Chlorfenapyr molecular weight is 407.6 g/mol.…”

“…These parameters should be studied and have to fall in the criteria range, unless justified. Although dissipation of chlorfenapyr was previously studied in peach (Galietta et al, 2011), pakchoi (Ou, Huang, Wang, & Fan, 2006), leek (Rahman et al, 2012), chili and cabbage (Ditya, Das, Sarkar, & Bhattacharyya, 2010) and in grapes and vines (Abdallah, Almaz, Arief, & Abd El-Aleem, 2014), it was not studied in okra or squash fruits.…”

“…Pesticide dissipation rate is affected by many factors e.g. crop, formulation type, temperature, irrigation and light (Galietta et al, 2011). Dissipation rate and set maximum residue limit MRL influence the pre-harvest interval PHI (Fenoll, Ruiz, Hellın, Lacasa, & Flores, 2009).…”