maneb and fenamidone

The dynamics and residues of mixed formulation of fenamidone and mancozeb in a gherkin field ecosystem were investigated. The quantification was performed using gas chromatography-electron capture detection (GC-ECD) and UV-vis spectrophotometry for fenamidone and mancozeb residues, respectively. The method was validated using blank samples spiked at three levels and the results showed that recoveries ranged from 92 to 98 and 90 to 96 percent with relative standard deviations (RSD) ranging of 0.78-5.9 and 2.04-4.41 percent for fenamidone and mancozeb, respectively. The compound degradation followed a first order kinetics with half-lives of 2.8-2.82 and 2.02-2.26 days, for fenamidone and mancozeb, respectively. Pesticide residues in fruit were below the EU maximum residue level (MRL) after 10 days for fenamidone (0.02 µg/g) and just after treatment for mancozeb (2 µg/g). These results can be utilized in formulating the spray schedule and safety evaluation for these pesticides in gherkin.

Topics: Chromatography, Gas; Cucumis; Ecosystem; Fruit; Fungicides, Industrial; Imidazolines; Kinetics; Maneb; Pesticide Residues; Strobilurins; Zineb

Residue dynamics of fenamidone and mancozeb on gherkin was evaluated at two different agro climatic zones i.e. at Bangalore (Zone-1) and Dharwad (Zone-2) in the state of Karnataka, India. Two treatments of the combination formulation (fenamidone 10% + mancozeb 50%) were given at the standard dose 150 + 750 g a.i. ha(-1) and double dose 300 + 1,500 g a.i. ha(-1). Initial residue deposits of fenamidone were 0.467 and 0.474 mg kg(-1) at Zone-1 and 2, respectively from standard dose treatment. From double dose treatment they were 0.964 and 0.856 mg kg(-1), respectively. Fenamidone residues persisted for 15 and 10 days and dissipated with the half-life of 4 and 3 days at Zone-1 and 2, respectively. Mancozeb residue deposits on gherkin were 0.383 and 0.428 mg kg(-1) from standard dose and 0.727 and 0.626 mg kg(-1) from double dose treatment at Zone-1 and 2, respectively. Mancozeb residues dissipated with the half-life of 2 and 1 day, respectively. Residues of both fenamidone and mancozeb dissipated faster at Zone-2 compared to Zone-1. The limit of quantification of fenamidone and mancozeb were 0.02 and 0.1 mg kg(-1), respectively in both gherkin and soil. Residues of fenamidone and mancozeb in soil collected on the 20th day from the 2 locations were found to be below quantifiable limit of both fungicides.

Topics: Climate; Cucumis sativus; Environmental Monitoring; Fungicides, Industrial; Imidazolines; India; Maneb; Pesticide Residues; Strobilurins; Zineb

Resistance to QoI fungicides (strobilurins, famoxadone and fenamidone) in populations of Plasmopara viticola (Berk & Curt) Berlese & de Toni developed soon after their introduction in France and Italy. Current resistance management strategies include limitation of the number of applications, use of mixtures and alternation of fungicides with different modes of action. The selection pressure resulting from QoI fungicides applied alone or in mixtures with non-QoI fungicides was investigated in whole plant experiments under controlled conditions. QoI-resistant populations of P. viticola gradually reverted to full sensitivity following consecutive transfers to untreated plants, suggesting that resistant phenotypes were less competitive than sensitive ones. When cycled on QoI-treated plants, reduction in sensitivity was greater for the QoI fungicide which had greater intrinsic activity on P. viticola. Sensitivity decreased at each subsequent cycle, resulting in almost full resistance after four generations. Mixture experiments indicated that selection pressure was affected most by the dose of the QoI fungicide and the nature of the partner fungicide. Folpet delayed selection pressure most effectively when it was associated with famoxadone or azoxystrobin. Mancozeb was least effective at reducing the rate of selection compared with the QoI alone, and fosetyl-aluminium was intermediate. Higher rates of selection were recorded when the dose of the QoI fungicide, solo or in a mixture, was increased from 1 to 4 microg ml(-1). Increasing the dose of the non-QoI partner fungicide in the mixture from 10 to 30 microg ml(-1) resulted in reduced selection pressure. These results suggest that the choice of the fungicide partner and its dosage in the mixture can significantly affect the success of QoI resistance management strategies under practical conditions.

Topics: Drug Interactions; Drug Resistance, Fungal; Fungicides, Industrial; Imidazolines; Maneb; Methacrylates; Oomycetes; Organophosphorus Compounds; Oxazoles; Phthalimides; Plant Diseases; Pyrimidines; Selection, Genetic; Strobilurins; Vitis; Zineb