the effect of simulated rain on folpet and mancozeb residues on grapes and on vine leaves

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  • This article was downloaded by: [University of Haifa Library]On: 16 May 2013, At: 09:33Publisher: Taylor & FrancisInforma Ltd Registered in England and Wales Registered Number: 1072954 Registered office: MortimerHouse, 37-41 Mortimer Street, London W1T 3JH, UK

    Journal of Environmental Science and Health, PartB: Pesticides, Food Contaminants, and AgriculturalWastesPublication details, including instructions for authors and subscription information:http://www.tandfonline.com/loi/lesb20

    THE EFFECT OF SIMULATED RAIN ON FOLPET ANDMANCOZEB RESIDUES ON GRAPES AND ON VINELEAVESPaolo Cabras a , Alberto Angioni a , Vincenzo L. Garau a , Marinella Melis a , Filippo M.Pirisi a , Franco Cabitza b & Mario Pala ba Dipartimento di Tossicologia, Universita di Cagliari, Cagliari, Italyb Centro Regionale Agrario Sperimentale, Cagliari, ItalyPublished online: 06 Feb 2007.

    To cite this article: Paolo Cabras , Alberto Angioni , Vincenzo L. Garau , Marinella Melis , Filippo M. Pirisi , Franco Cabitza& Mario Pala (2001): THE EFFECT OF SIMULATED RAIN ON FOLPET AND MANCOZEB RESIDUES ON GRAPES AND ON VINELEAVES, Journal of Environmental Science and Health, Part B: Pesticides, Food Contaminants, and Agricultural Wastes,36:5, 609-618

    To link to this article: http://dx.doi.org/10.1081/PFC-100106189

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  • J. ENVIRON. SCI. HEALTH, B36(5), 609618 (2001)

    THE EFFECT OF SIMULATED RAINON FOLPET AND MANCOZEB RESIDUES

    ON GRAPES AND ON VINE LEAVES

    Paolo Cabras,1,* Alberto Angioni,1 Vincenzo L. Garau,1Marinella Melis,1 Filippo M. Pirisi,1 Franco Cabitza,2

    and Mario Pala2

    1Dipartimento di Tossicologia, Universita` di Cagliari, Cagliari, Italy2 Centro Regionale Agrario Sperimentale, Cagliari, Italy

    ABSTRACT

    Artificial rainfalls were used to determine the effect of the amount of the rain-fall and the time interval between pesticide application and rainfall event, onfolpet and mancozeb residues on grapes and vine leaves. Forty-five mm ofrain were administered to the vineyard in different amounts (45; 3015;151515 mm). Folpet showed good rainfastness on the grapes and on theleaves. A modest decrease was observed only in the experiments that had re-ceived 45 mm of rain at one go. Mancozeb showed a lower rainfastness, sincea portion of the deposit was easily washed off also by a modest rainfall. Thepercentage of this portion was higher in the grapes (38%) than in the leaves(20%). The data obtained in these experiments show that, in the case of folpet,it is not necessary to repeat the treatment when it rains the day after, while it isrecommendable to repeat it in the case of mancozeb.

    Key Words: Folpet; Mancozeb; Washoff; Rain; Residues

    609

    Copyright 2001 by Marcel Dekker, Inc. www.dekker.com

    *Corresponding author. E-mail: pcabrasunica.it

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    INTRODUCTION

    Pesticides have two modes of action: the systemic and the contact action.Systemic pesticides penetrate the plant, while nonsystemic pesticides lie on itssurface and, depending on their chemical-physical characteristics, may diffuse intothe epicuticular waxes (1). The behaviour of rainfall shortly after treatment is dif-ferent in these two categories of pesticides, having no effect on the systemic pes-ticide, while in the nonsystemic, the portion of pesticide that is not diffused intothe epicuticular wax may be washed off. Since a loss in active ingredient (a.i.)could cause a loss in efficacy (2 4) it is important to know the behaviour of thepesticides in response to washoff, especially when it rains shortly after the treat-ment. Among the many factors that could affect washoff are: rain intensity, rainamount, interval of time between treatments and rainfall, commercial formula-tion of pesticides, solubility in water of pesticides, and type of crop. Some papers(59) have shown that the effect of the amount of rainfall on pesticide washoff isgreater than that of its intensity. Pesticide rainfastness to washoff is higher whenthe formulate contains surfactants (10 12).The time between treatments and rain-fall deeply affects the washoff effect, but this depends on the pesticide and/or theformulation (9, 1317). Downy mildew (Plasmopora viticola) is the most impor-tant cryptogamic disease of vine; it strikes grapes and leaves. Folpet (N-(trichloro-methylthio)phthalimide) and mancozeb (manganese ethylenebis (dithiocarbamate)(polymeric) complex with zinc salt) are two non systemic fungicides with pro-tective action extensively used to control this parasite for their low resistance-generating risk. Experience has taught that are necessary 4 5 treatments withintervals of 78 and 810 days for mancozeb and folpet, respectively, when envi-ronmental conditions are favourable to the growth of the disease. Solubility inwater is 0.8 mg/l for Folpet and 6.2 mg/l for mancozeb (18); therefore a plentifulrainfall could washoff pesticides and reduce their efficacy. No studies have beenfound in literature on the dynamics of pesticide washoff by rainfall in vine and, toour knowledge, the whashoff of folpet and mancozeb had not been studied in othercrops as well. In this study some experiments have been carried out to determineby simulated rains the effect of the amount of rain on fruits and vine leaves andthat of the time lapse between treatment and rainfall on the residues of folpet andmancozeb.

    MATERIALS AND METHODS

    Experimental Preparation

    Field Trials

    The trials were carried out on a grape vineyard (cv. Chardonnay), located atUssana, near Cagliari, Italy. The plant distance was of 2.5 1.5m. A random blockscheme with four replicates for each experiment was used. Every plot consisted of30 plants. Treatments were carried out on June 18, 28, and July 9 and 19, 1999.

    610 CABRAS ET AL.

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    Folpan 80 WDG (80% folpet) and M 70 (70% Mancozeb) were applied at the dosesrecommended by the manufacturers (125 g/hl e 200 g/hl respectively; 10 hl/ha)with a portable motor sprayer (AM150, Oleo-Mac, Reggio Emilia, Italy).

    Artificial Rain

    An overhead irrigation pipeline was placed above the rows, with sprinklersmounted on alternate sides at 3.0 m intervals, without overlapping any of the areascovered by the sprinklers. The vineyard was divided into three blocks, A, B and C,and 45 mm of rain were administered to each block. On the day after the lasttreatment, 15, 30, and 45 mm of artificial rain were given respectively to blocks A,B, and C. Two days later, a further 15 mm were given to blocks A and B, and afteranother two days yet another 15 mm only to block A. The intensity of the appliedrain was constant at 60 mmh1.

    Sampling

    The samples (2 kg of grapes, and 20 mature leaves) were collected before andafter each artificial rainfall, and ten days after the last pesticide application. Mete-orological data were constantly recorded with an AD-2 automatic weather station(SILIMET, Modena), located near the vineyard. During the trials the maximumand minimum temperatures were 32.2 and 16.7C. No precipitation was registeredduring the experiments.

    Pesticides Analysis

    Folpet and its metabolite phthalimide were analysed as reported in Cabraset al., (19), while mancozeb was detected following the spectrophotometric meth-ods described by Keppel (20).

    Chemicals

    The pesticides were all analytical standards. Folpet, mancozeb and vinclo-zolin were purchased from Ehrenstorfer (Augsburg, Germany), and phthalimidefrom Lancaster Synthesis (Muhleim am Main, Germany). Acetone, benzene andpetroleum ether were pure solvents for analysis (Carlo Erba, Milan, Italy), Sodiumchloride, stannous chloride, cupric acetate, and diethanolamine were analyticalgrade reagents (Carlo Erba).

    Standard stock solutions (ca. 400 mg/kg) of folpet and phthalimide wereprepared in acetone. For GC analysis vinclozolin (99%) was used as an internalstandard (i.s.) at 0.6 mg/Kg. Working standard solutions were obtained by dilutionwith the extract containing the i.s. of untreated grapes and leaves.

    FOLPET AND MANCOZEB RESIDUES 611

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    Folpet Analysis

    Gas chromatographic (GC) determination. An HRGC Mega 2 (Fison, Mi-lano, Italia), equipped with an ECD 800 detector, a split-splitless injector, an AS800 autosampler, and a HP 3396 A (Hewlett Packard, Avondale, PA, USA) inte-grator, was used. The capillary column was WCOT silica fused column, CP Sil8CB low bleed/MS (30 m 0.25 mm i.d., 0.10 mm, Chrompack,

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