Mancozeb Research Articles

Effects of mancozeb on the activities of murine peritoneal macrophagesin vitro andex vivo

Mancozeb (MCZ) is known to have detrimental effects on the reproductive system, but the toxicity of MCZ on immune responses has not been systematically investigated. We investigated the effects of MCZ exposure on the activities of murine peritoneal macrophages through evaluation of MCZ-induced alteration of nitric oxide (NO) production and tumor necrosis factor-alpha (TNF-alpha) synthesis. Macrophages were examined ex vivo from mice orally treated with various doses of MCZ for 5 consecutive days per week for 4 weeks (subacute exposure, 250, 1000, 1500 mg/kg/day) followed by culture for 2 (TNF-alpha) or 3 days (NO) in the presence of LPS plus IFN-gamma. Macrophages from naive mice were also cultured with various concentrations of MCZ (0.05, 0.25, 0.5, 1 and 2 microg/mIL in the presence of LPS plus IFN-gamma for 2 (TNF-alpha) or 3 days (NO) in vitro. NO production was decreased with the in vitro exposure to all concentrations of MCZ. However, the amount of NO production by peritoneal macrophages from MCZ-subacutely exposed mice was increased in comparision with that of control group. In vitro, MCZ suppressed TNF-alpha secretion with significant reduction at 2 microg/mL MCZ. Conversely, TNF-alpha release was enhanced ex vivo. This study provides the substantial evidence on MCZ-induced alternation in macrophage activity. In order to clearly understand the contrasting effect of MCZ on peritoneal macrophage activity, it is necessary to further investigate the influence of major metabolite of MCZ (ETU) exposure on the NO production and TNF-alpha synthesis.

In vivo effect of some fungicides on the development of Pyricularia grisea and Helminthosporium oryzae

The effect of various fungicide treatments of seeds and leaves of rice on the development of the pathogenic fungi Pyricularia grisea and Helminthosporium oryzae was studied. When applied to seeds, tricyclazole, mancozeb and the carboxin+thiram combination were the only fungicides that reduced all the symptoms induced by both pathogens without damaging the development of young plants. Tricyclazole and the tricyclazole+mancozeb protected rice plants against P. grisea and H. oryzae respectively throughout the vegetative phase. To ensure protection during the entire vegetative phase, pyrazophos should be applied every two weeks while the carboxin+thiram combination, thiabendazole and mancozeb should be applied every week.

Commercial Fungicide Formulations Induce In Vitro Oospore Formation and Phenotypic Change in Mating Type in Phytophthora infestans

ABSTRACT A wide range of commercially formulated fungicides cause in vitro effects on mating behavior in specific isolates of Phytophthora infestans, the causal agent of late blight of potato and tomato. Four isolates of P. infestans representing each of the four common US genotypes, US-1, US-6, US-7, and US-8 and varying in their sensitivity to metalaxyl, were exposed to a variety of fungicides used to control late blight in petri dish assays at concentrations ranging from 1 to 100 mug a.i./ml. Exposure of each of these normally heterothallic single mating type isolates of P. infestans to 9 of the 11 commercial fungicide formulations tested resulted in the formation of oospores after 2 to 4 weeks. The highest numbers of oospores were formed on media amended with Ridomil 2E (metalaxyl) and Ridomil Gold EC (mefenoxam) at 0.1 to 10 mug a.i./ml, averaging as many as 471 and 450 oospores per petri dish, respectively. Several other fungicides including Maneb, Manzate (Mancozeb), Curzate (cymoxanil + mancozeb), and Acrobat MZ (dimethomorph + mancozeb) also induced oospore formation, producing from 0 to 200 oospores per plate at fungicide concentrations from 0.1 to 10 mug a.i./ml. The metalaxyl resistant isolates formed oospores in response to the fungicides more often than the metalaxyl sensitive isolates. No oospores were formed on media amended with Bravo (chlorothalonil) or Tattoo C (chlorothalonil + propamocarb HCl) and these compounds completely suppressed growth of the isolates at 0.1 and 1 mug a.i./ml. Three metalaxyl resistant A2 isolates mated with both A1 and A2 isolates after exposure to the fungicides Ridomil 2E and Ridomil Gold EC. Alterations in mating type expression were also observed in a metalaxyl sensitive A1 isolate after exposure to Benlate (benomyl). Copious amounts of chemicals are applied annually to potato and tomato production areas to control late blight. Our results indicate that a wide range of chemically diverse fungicides can induce normally heterothallic metalaxyl resistant isolates of P. infestans to form oospores in vitro after short exposures to the fungicides.

Fungicidal control ofPhytophthora erythroseptica: The cause of pink rot on potato

Two shade house and six field experiments were undertaken to evaluate fungicides and timing of application for the control of pink rot of potatoes caused byPhytophthora erythroseptica. Pink rot developed in up to 60% of tubers grown in artificially inoculated soil and 21% of the tubers in naturally infected soil. Ridomil (metalaxyl) and Ridomil Gold (mefenoxan) granules applied to the soil at planting completely or nearly completely controlled pink rot throughout the season in both pot and field experiments. Foliar applications of Ridomil Gold MZ (mefenoxan plus mancozeb) applied when tubers were around 20 mm diameter and another one or two sprays 12 to 28 days later also provided more than 80% control of pink rot in most experiments. Foliar applications of Shirlan (fluazanim) or Acrobat MZ (dimethomorph plus mancozeb) showed some activity against pink rot, but were significantly less effective than Ridomil Gold MZ. Foli-R-Fos 200 (phosphonic acid) or Dithane M45 (mancozeb) applied to the canopy showed little activity against pink rot in most experiments. Yield increases of between 6 and 17 tons ha−1 resulted from the application of either Ridomil granules at planting or two to three Ridomil Gold MZ foliar sprays around “tuber set.”

Sensitivity of Entomopathogenic Fungi, Beauveria Bassiana and Metarhizium Anisopliae to Selected Fungicides

Eight commercial fungicides were evaluated in vitro on entomopathogenic fungi, Beauveria bassiana and Metarhizium anisopliae. A pesticide-YPD agar disc method (7 days at 25℃) was used to study the effect of pesticides on the mycelial growth and sporulation of B. bassiana and M. anisopliae. Among the fungicides, propineb (Pro), imazalil (Ima), and metalaxyl + mancozeb (MM), were fungicidal to B. bassiana and M. anisopliae for all the isolates at all tested concentrations. Bupirimate (Bup) at the tested concentrations showed moderate inhibition to B. bassiana but not to M. anisopliae. Zineb caused various degrees of inhibited growth and conidial production for the tested isolates. All the fungi showed a little growth and sporulation when they grew on Iprodione-YPD agar plates. Thiophenate methyl + streptomycin (TSM) was toxic to M. anisopliae and B. bassiana; however, a little growth and sporulation occurred when the fungi were transferred to fungicide-free YPD plates (except M. anisopliae iso. 195). All the concentrations of metalaxyl + copper oxychloride (MCO) caused inhibition to B. bassiana and M. anisopliae.

Foliar Fungicides as Protective Seed Piece Treatments for Management of Late Blight of Potatoes.

Fungicides receiving Section 18 emergency exemptions for management of the foliar phase of late blight of potato were evaluated as protective treatments for control of tuberborne inoculum of Phytophthora infestans in greenhouse and field studies. Three Section 18 products, Acrobat MZ (dimethomorph + mancozeb), Curzate M-8 (cymoxanil + mancozeb), and Tattoo C (propamocarb hydrochloride + chlorothalonil), when applied to the seed piece prior to inoculation with P. infestans, significantly (P ≤ 0.05) increased sprout emergence, compared with the inoculated water control. Of the three Section 18 products, Curzate M-8 was frequently the most effective. The increase in plant emergence with the protective seed piece treatment was seen with cultivars that differ in susceptibility to late blight, two genotypes (US-8 and US-11) of P. infestans, zoospore and sporangial inocula, and at different inoculation sites on the seed piece. In greenhouse studies, percent emergence with the protective seed piece treatments averaged 74% for cv. White Rose and 44% for cv. Shepody, compared with 9 and 8% for the inoculated water control of the respective cultivars. In field studies, when inoculum was placed either adjacent to or 4 cm away from the sprout, plant emergence of the inoculated water control was 12 and 36%, respectively. Application of the fungicides to the seed piece prior to inoculation increased emergence by an average of 700 and 212% for the respective inoculation sites. There was no evidence for translocation of the fungicides to the emerging foliage in concentrations high enough to prevent foliar infection from airborne inoculum of P. infestans. Control of tuberborne inoculum of P. infestans with appropriate seed piece treatments will result in an increase in plant emergence and improved crop uniformity.

Susceptibility of two strains of Amblyseius andersoni Chant. (Acari: phytoseiidae) to dithiocarbamate fungicides

The effect of five fungicides on adult female mortality, fecundity, egg hatch and on larval mortality was examined in the laboratory using a fungicide-susceptible and a fungicide-resistant strain of the predaceous phytoseiid mite, Amblyseius andersoni Chant. The combined effect of each fungicide was compared using a coefficient of toxicity computed using the above four toxicity factors. The susceptible and resistant strains were most affected by the bidithiocarbommate fungicides mancozeb, metiram and propineb. Ziram and dithianon had little effect on the S strain and ziram had little effect on the R strain. The toxicity of dithianon was not tested using the R strain. A resistance factor (LC50 R strain: LC50 S strain) of 6.13 for mancozeb was estimated for the R strain. Mancozeb resistance was a heritable trait and was primarily associated with the adult female.

Ziram, thiram, dithane M-45

Ziram, thiram, dithane M-45

Degradation of dithane M-45 residues in brinjals during cooking

Degradation of dithane M-45 residues in brinjals during cooking

Contrôle da cercosporiose do caqui

Os autores fizeram levantamento do grau de resistência em variedades de caqui à Cercosporiose, e concluiram que há variação da resistência entre as principais variedades cultivadas no Estado de São Paulo. Em ensaios com pulverização fungicidas, Maneb (Dithne M-22) mostrou ser mais eficiente que a calda bordalêsa no contrôle da doença.