Synergism in fungicide mixtures againstPseudoperonospora Cubensis

Mixtures of cymoxanil with mancozeb (Mancur) or with mancozeb plus oxadixyl (Pulsan, Sandocur-M) were effective in controlling either metalaxyl-sensitive (MS) or -resistant (MR) isolates ofPseudoperonospora cubensis on cucumbers (cv. ‘Elem’) in growth chambers. Metalaxyl+mancozeb (Ridomil-MZ) and oxadixyl+mancozeb (SAN-518) mixtures were effective against the metalaxyl-sensitive but less so against the metalaxyl-resistant isolate. Fungicide mixtures were far more effective in controlling either the sensitive or the resistant isolates than were the individual components applied alone, thereby representing significant levels of synergistic interactions. Increased efficacy of mixtures relative to their combined components (synergy factor) was calculated by the Wadley method. Mixtures containing cymoxanil showed high synergy factors against the resistant isolate, whereas Ridomil-MZ and SAN-518 did not evince this phenomenon. We concluded that cymoxanil mixtures might be suitable for the control of downy mildew incited by a metalaxyl-resistant isolate ofP. cubensis.     

Chemical control of late blight epidemics incited by metalaxyl-resistantPhytophthora infestans in potato crops in Israel

Four field trials were conducted to evaluate the efficacy of various fungicide formulations in controlling late blight in potato crops artificially inoculated with A₂ metalaxyl-resistant isolates ofPhytophthora infestans. Two trials (Winter 1986, Spring 1987) were performed at the research farm of Bar-IIan University (central coastal plain) and two trials (Winter 1987, Spring 1988) at the Besor Experiment Farm (western Negev), with seven formulations tested in each trial. At Bar-IIan, Mancur (mancozeb + cymoxanil, 4:1) applied once a week was most effective in controlling the blight. Sandocur-M and Pulsan (mancozeb + oxadixyl + cymoxanil, 7:1:2 and 7:1:0.4, respectively) applied at biweekly intervals were the second best, while SAN 518F (mancozeb + oxadixyl, 7:1) and Ridomil-MZ (mancozeb + metalaxyl, 7.5:1) applied at biweekly intervals, and mancozeb or cymoxanil applied once a week, were the least effective. At the Besor farm Ridomil-MZ at biweekly intervals was the least effective, but the efficacy of the other formulations varied between the two trials. Mancur, Sandocur-M, Previcur-N and mancozeb were highly effective in Winter 1987 but less so in Spring 1988. In the latter season Mancur, Sandocur-M and Previcur-N were significantly more effective than mancozeb or Ridomil-MZ. The correlation coefficient between yield and final disease level was -0.5322.     

Resistance to metalaxyl in isolates of the sunflower pathogen Plasmopara halstedii

Plasmopara halstedii isolates showing an atypical reaction to metalaxyl were collected in France, in 1995 and 1996, and tested in the laboratory for their level of sensitivity to this fungicide. Primary and secondary infections caused by one of these isolates were not controlled by the metalaxyl concentration registered for seed treatment. The EC₅₀ of this isolate was 12 800 mg a.i. kg^-1 compared with 22 mg a.i. kg^-1 for sensitive isolate, indicating a 582-fold decrease in sensitivity to the compound. There was no reduction in the agressiveness of the resistant isolate. Using other anti-oomycete fungicides, it appeared that propamocarb, contact fungicides (fluazinam, folpet, mancozeb) and the mixed formulations dimethomorph + mancozeb, cymoxanil + mancozeb and ofurace + folpet were effective against primary infections made with metalaxyl resistant and sensitive isolates, but not against secondary infections. Metalaxyl mixed with fluazinam, folpet or mancozeb was more effective against primary infections with the resistant isolate than metalaxyl alone. The EC₅₀ of five other isolates ranged from 5 800 to 32 900 mg a.i. kg^-1, indicating a variability in metalaxyl sensitivity of resistant sunflower downy mildew isolates. This is the first report of physiological resistance to metalaxyl in Plasmopara halstedii.     

防治大豆疫霉根腐病的药剂筛选

在离体条件下测定了 8种内吸性杀菌剂对大豆疫霉菌菌丝生长的抑制作用。甲霜灵、甲霜灵锰锌、安克锰锌、杀毒矾、霜脲锰锌、克露和加瑞农为有效杀菌剂 ,霜霉威不具有抑菌效果。甲霜灵的 EC50 值为0 .4 870 μg/ m L,抑菌效果最好 ,安克锰锌、甲霜灵锰锌的 EC50 值分别为 1.4 2 6 1μg/ m L和 1.76 97μg/ m L,效果次之。在活体条件下 ,甲霜灵和甲霜灵锰锌能完全抑制大豆疫霉菌对感病大豆品种的侵入 ,并具有较长的药效期 ,安克锰锌、杀毒矾和霜霉威虽然具有明显的防治效果但药效期很短。大豆疫霉菌菌株间对甲霜灵锰锌的敏感性存在差异 ,但这种差异与菌株来源没有相关性 ,EC50 平均值为 1.830 2μg/ m L ,没有发现耐药性菌株。在我国黑龙江省目前缺乏有效抗病品种的情况下 ,建议应用甲霜灵锰锌防治大豆疫霉根腐病。     

霜脲氰与不同杀菌剂混配对两种霜霉病菌的增效作用

采用叶盘法（定量喷药）测定霜脲氰与不同杀菌剂混配对黄瓜和葡萄霜霉病菌抗甲霜灵菌株的增效作用,证实了霜脲氰加代森锰锌或二者再加恶霜灵以不同比率混配对黄瓜、葡萄霜霉病菌均明显增效,发现了霜脲氰与碱式硫酸铜1：8混配对黄瓜霜霉病菌增交,代森锰锌（1：8）或再加恶霜灵（1：8：1）对葡萄霜霉病菌的增效作用随着供试菌株对甲霜灵抗性水平的提高而增强。霜脲氰与代森锰锌1：7混配以保护、治疗、铲除方式处理黄瓜叶盘,对黄瓜霜霉病菌均表现增效。     

Toxicity of propamocarb to the late blight fungus on potato

Propamocarb (Previcur-N; propyl-[3-dimethylamino-propyl] carbamate-monohydrochloride) was testedin vivo against 32 field isolates ofPhytophthora infestans from six countries. Fungicide dosages required to achieve 90% control of the blight ranged between 676 and 1530 ppm a.i. in potted potato (cv. ‘Alpha’) plants and between 1135 and 2648 ppm in potato tuber slices. Isolates from Israel were less sensitive to the fungicide than isolates from Europe or North America. Toxicity of propamocarb was not related to resistance or sensitivity to phenylamide fungicides (e.g. metalaxyl). Nevertheless, most metalaxyl-resistant isolates from Israel were less sensitive to propamocarb than most metalaxyl-sensitive isolates from this country. Monocyclic epidemics conducted with the 20 Israeli isolates in the field showed that 1081–2012 ppm of the fungicide was required to achieve 90% control of the disease. Laboratory experiments revealed that the fungicide was poorly active against sporangial germination and had a limited curative efficacy. It exhibited a translaminar translocation in leaves but a poor acropetal or basipetal systemicity from foliage. Propamocarb + mancozeb mixtures (1:1, v/w) were synergistically effective in controlling the blight. Growers in Israel use tank mixtures of propamocarb (Dynone) and mancozeb to combat late blight in potato fields where phenylamide-resistant isolates ofP. infestans are prevalent.     

Variations among field isolates of Botrytis cinerea in their sensitivity to antifungal compounds

Seventeen field isolates of Botrytis cinerea were compared by determining their radial growth on synthetic media containing various amounts of 21 antifungal compounds. Twelve of these compounds were fungicides that are recommended for the control of Botrytis infections. There were marked differences between the isolates in their sensitivity to the compounds. Individual isolates displayed high levels of resistance to some of the fungicides, including benomyl, carbendazim, iprodione, thiabendazole, thiophanate-methyl, vinclozolin and zineb. The most potent growth inhibitors were benomyl and carbendazim (ED₉₅ values for most isolates <0.1 μg fungicide ml^?1 media), dichlofluanid, iprodione, nystatin, thiabendazole, thiophanatemethyl and vinclozolin (ED₉₅ values for most isolates < 1.0 μg ml^?1), and captan, chlorothalonil, dicloran and thiram (ED₉₅ values for most isolates < 6.0 μg ml^?1). Zineb was much less potent than the other recommended anti-Botrytis fungicides; it was no more effective than carboxin, dinocap and mancozeb (ED₉₅ values for most isolates > 25 μg ml^?1).     

葡萄霜霉病菌和马铃薯晚疫病菌对三种杀菌剂的抗药性风险研究

 葡萄霜霉病菌经UV诱导4次得5个抗烯酰吗啉菌株,其适合度较原菌株B951差,竞争力较弱,该菌经药剂驯化7代对恶霜灵产生抗性,但未对烯酰吗啉及霜脲氰产生抗性,UV诱导4次对霜脲氰及恶霜灵均未产生抗性。相比之下,马铃薯晚疫病菌经UV诱导11次得7个抗恶霜灵菌株,其中菌株UO1适合度好于其原菌株,竞争力较强。马铃薯晚疫病菌经过药剂驯化3代对恶霜灵产生了抗性,但是经UV诱导8~11次和药剂驯化30代对烯酰吗啉和霜脲氰仍保持敏感。     

黄瓜和葡萄霜霉病菌对不同内吸杀菌剂的交互抗药性

为了确定甲霜胺、乙磷铝与恶唑烷酮、霜脲氰、安克和硫代磷酰胺酯之间的交抗型,在叶盘上共测试了黄瓜霜霉(PC)和葡萄霜霉(PV)的27个分离系对6种内吸杀菌剂的抗药水平,结果证实了在两种目标真菌上甲霜胺和乙磷铝之间的非交抗关系,甲霜胺和恶唑烷酮之间的正交互抗药性,在PC上甲霜胺和霜脲氰之间的非交抗关系。试验还表明在PC上甲霜胺和安克之间以及乙磷铝和霜脲氰之间的非交抗关系,在PV上甲霜胺和乙磷铝与硫代磷酰胺酯之间的非交抗关系。此外,试验发现了霜脲氰和安克在叶盘上对抗甲霜胺分离系具有很高的杀菌活性。     

In-vivo evaluation of adjuvants for more effective control of celery leaf-spot (Septoria apiicola) and powdery mildew (Erysiphe graminis) of wheat with fungicides

The effects of seven adjuvants (at 0, 0.5, 1.0 and 2.0 g litre^?1) on the efficacies of four fungicides al 0.5 g litre^?1 were studied in the laboratory for the control of leaf-spot in celery (caused by Septoria apiicola) and powdery mildew on winter wheat (caused by Erysiphe graminis). The most effective fungicides for controlling leaf-spot were: tebuconazole + triadimenol = flutriafol > mancozeb + oxadixyl > prochloraz. However, addition of adjuvant to the fungicides gave a modified pattern of effectiveness. The efficacy of flutriafol was strongly enhanced by addition of all adjuvants, but those of prochloraz and mancozeb+oxadixyl only partially so. The tested adjuvants were mineral oil + surfactant, a polymer/alkoxylated alkyl ether blend, an ethoxylated alkylphenol, an ethoxylated hexitan ester blend, an ethoxylated nonylphenol and an alkylpolysaccharide- based adjuvant mixture. However, the addition of adjuvants to tebuconazole + triadimenol had a negative effect. Of all the adjuvants tested, the nonylphenol ethoxylate and a mixture of mineral oil /surfactant and alkylpolysaccharides gave the highest efficacy with the fungicides, while the mineral oil/surfactant and the alkylpolysaccharides alone were less effective. There was a positive relationship between high concentrations of adjuvants and their effectiveness, but there were some exceptions. The most effective fungicides for control of powdery mildew in wheat were prochloraz, mancozeb + oxadixyl and tebuconazole + triadimenol. There was a linear relationship between the high efficacy of the fungicide and the concentration of adjuvants to control powdery mildew in wheat. The highest concentration of adjuvant (2-0 g litre^?1) gave the highest efficacy for the fungicides.     

Within‐ and between‐orchard variability in the sensitivity of Venturia inaequalis to myclobutanil,a DMI fungicide,in the UK

BACKGROUND: Myclobutanil, a demethylation inhibitor (DMI) fungicide, is an important fungicide for controlling apple scab and powdery mildew. Overuse of this fungicide has led to establishment of scab isolates with reduced sensitivity to this fungicide in several countries. Experiments were conducted to determine the sensitivity of the causal agent of apple scab, Venturia inaequalis (Cooke) Winter, to myclobutanil in the UK, in order to assess whether there is a relationship between fungal insensitivity and the number of DMI applications, and establishing whether fungal sensitivity varied greatly within an orchard. RESULTS: Reduced sensitivity of V. inaequalis to myclobutanil was positively related linearly to the number of DMI applications. ED₅₀ values ranged from 0.028 to 1.017 mg L^?1 (average = 0.292) for the baseline population, whereas isolates from two other orchards had much greater ED₅₀ values, ranging from 0.085 to 5.213 mg L^?1 (average = 1.852). There was significant variation in fungal sensitivity to myclobutanil among fungal isolates from different locations within a single orchard. CONCLUSIONS: Spatial spread of insensitive isolates of V. inaequalis to myclobutanil is likely to be limited in distance. Conidia may be an important source of primary inoculum. Myclobutanil should still be effective for most field isolates, but its use should be strategically integrated with other groups of fungicides. Copyright © 2009 Society of Chemical Industry     

Activity and metabolism of cyano-oxime derivatives in various strains of Botrytis cinerea

The fungitoxicity of cymoxanil, 4 cyano-oxime analogs (in which the acetylurea group was replaced with various groups: amide, ester, propargyl, and cyanomethyl-amide), and 2 cymoxanil-metabolites was studied against various strains of Botrytis cinerea. The fungicidal effect was measured on germ-tube elongation and mycelial growth. Cymoxanil and the analogs bearing the amide and ester groups showed the best anti-botrytis activity. The strains studied can be classified into 3 groups according to the germ-tube sensitivity to cyano-oximes. These groups fitted well with the 3 phenotypes of sensitivity to cymoxanil previously characterized in our laboratory: CyaS₁ (highly sensitive phenotype); CyaS₂ (moderately sensitive phenotype); and CyaR (tolerant phenotype). The bio-transformations of all the cyano-oximes were monitored in the culture-medium of the different strains using HPLC- and IP-HPTLC-methods. HPLC-studies showed that cymoxanil and the analogs bearing the groups amide and ester were quickly metabolized in the culture-medium of the CyaS₁ strain. Moreover, these studies allowed us to correlate disappearance of these cyano-oximes, to their fungicidal activity towards the CyaS₁ strain. This suggests that cyano-oximes and particularly cymoxanil are probably activated in a fungitoxic compound. IP-HPTLC-studies strengthened the precedent results and allowed us to correlate disappearance of cyano-oximes studied with appearance of two acids metabolites of hydrolysis. These metabolites could be the actual active-principles.     

Characterization of European Plasmopara viticola isolates with reduced sensitivity to cymoxanil

Cymoxanil has been used for over 30 years to control grape downy mildew (Plasmopara viticola) in European vineyards, prevalently in mixture with other fungicides active on this disease. In the 1990’s cases of P. viticola resistant to cymoxanil were detected using a leaf disc assay. In this study, we establish that the presence of only 1 % of resistant isolates in a P. viticola population will allow the detection of cymoxanil resistance in the leaf disc assay. A poor correlation (R?=?0.194) was observed between the leaf disc assay and a whole- plant test for 38 P. viticola field populations collected in 2004. Over 60 % of these populations were characterized as fully sensitive in a whole-plant assay compared to 10 % in the leaf disc assay. Five P. viticola field isolates resistant to cymoxanil reverted to full sensitivity after six to nine transfers to untreated vines, indicating that cymoxanil resistance in P. viticola is unstable. Two European P. viticola populations sensitive to cymoxanil became resistant when transferred 12–14 times on vines treated with cymoxanil. In contrast, two populations originating from the USA and three monozoospore isolates from France retained full sensitivity to the fungicide after 13 cycles on cymoxanil-treated plants. Whole-plant experiments were conducted in the laboratory to compare the efficiency of spray programs to delay the development of cymoxanil resistance. Whereas the continuous use of cymoxanil alone quickly selected for resistance, the mixture of cymoxanil and folpet applied either continuously or in strict or block alternation effectively prevented the development of resistance over 10 generations of the fungus. These results demonstrate that resistance to cymoxanil in P. viticola can be managed with appropriate spray programs.     

葡萄胶孢炭疽菌对3种麦角甾醇脱甲基抑制剂类杀菌剂的敏感性

系统比较了从云南省主要葡萄产区采集的57株葡萄胶胞炭疽菌Colletotrichum gloeosporioides对三唑类脱甲基抑制剂烯唑醇、腈菌唑及咪唑类脱甲基抑制剂咪鲜胺的敏感性、交互敏感性及敏感性与生存适合度的相关性等指标。结果表明:供试菌株对咪鲜胺的EC50值在0.01~1.58 mg/L之间,高于其对烯唑醇(EC50值为0.05~25.45 mg/L)和腈菌唑(EC50值为0.49~192.93 mg/L)的敏感性;部分菌株对烯唑醇和腈菌唑的敏感性显著降低,而对咪鲜胺仍保持较高的敏感性;供试菌株对烯唑醇和腈菌唑的敏感性具有显著的相关性,而对咪鲜胺的敏感性与对烯唑醇和腈菌唑的敏感性之间则无显著相关性。低敏感性菌株的致病力和菌落生长速率与敏感菌株无显著差异,具有较高的生存适合度。     

江西省辣椒疫霉病菌的交配型及对霜脲氰敏感性的测定

由辣椒疫霉病菌Phytophthora capsici引起的辣椒疫病是辣椒生产上一种重要病害,在我国各地均有发生.辣椒疫霉是一种异宗配合的卵菌.异宗配合的疫霉菌的不同交配型菌株成对培养时,可以形成有性器官并发生基因重组,使该种病菌获得更强的生存能力、致病力和更广泛的寄主范围.因此,研究疫霉交配型在理论和实践上均具有重要意义.霜脲氰(cymoxanil)由美国杜邦公司开发,用于卵菌纲病害的防治.自投入市场使用,至今未发现在自然条件下关于疫霉菌对霜脲氰抗药性报道.     

抑制番茄早疫病菌活性化合物的 高通量筛选方法研究

以OD 630 值作为评价指标,在高通量筛选设备上建立了番茄早疫病菌Alternaria solania的高通量定量筛选方法,并对嘧菌酯、百菌清、 NFDA1 醚唑、霜脲氰、甲霜灵、代森锰锌、福美双和咪鲜胺8种常用杀菌剂对番茄早疫病菌孢子萌发和菌丝生长的抑制效果进行了评价,结果与孢子萌发法和目测筛选法所得结论基本一致。     

Sensitivity of European Plasmopara viticola populations to cymoxanil

Between 1995 and 1997, 278 grape downy mildew (Plasmopara viticola) populations originating from European vineyards were characterised for their sensitivity to cymoxanil in a leaf-disc assay. The sensitivity profile revealed a wide distribution, with minimum inhibitory concentrations (MIC) ranging from 10 to more than 800 mg litre⁻¹. EC₅₀ values ranged from 1 to more than 800 mg litre⁻¹ with an average of 125 mg litre⁻¹. The sensitivity distribution was stable between 1995 and 1997. Surprisingly, populations from Portugal appeared significantly more sensitive than those from France or Italy, which could not be linked to differential cymoxanil usage in these countries. P viticola populations collected outside Europe and never exposed to cymoxanil appeared significantly more sensitive than exposed European populations, with an average EC₅₀ value of 10 mg litre⁻¹. The level of sensitivity of European P viticola populations was relatively unaffected by the number of cymoxanil applications made during a season or by the number of years of cymoxanil use. No link was found between the level of sensitivity in the leaf-disc assay and the level of performance of the cymoxanil mixtures used in the fields where the populations originated. Specific field trials conducted in Italy and Portugal have shown that the performance of cymoxanil-based mixtures remained good even on populations of the grape downy mildew fungus characterised as less sensitive in the leaf-disc assay. While there are no baseline sensitivity data for pre-commercialisation P viticola populations, the results of our study suggest that a shift in sensitivity (12.5-fold) may have occurred in some areas since introduction of cymoxanil on grapes nearly 20 years ago. Because cymoxanil is never used alone, it is difficult to determine whether or not practical resistance is occurring in European vineyards. © 1999 Society of Chemical Industry     

抗氟吡菌胺辣椒疫霉菌株的诱导及其生物学特性的研究

 采用菌丝生长速率法, 测定了采自泰安、平谷、杭州和昆明4个地区的42株辣椒疫霉病菌对氟吡菌胺的敏感性, 结果表明, 其EC₅₀值在0.618 ~0.927 μg·mL^-1之间, 平均EC₅₀ =(0.743±0.067 7) μg·mL^-1。 42个菌株对氟吡菌胺的敏感性分布呈单峰曲线, 未出现抗性的病原菌亚群体, 可将其单峰曲线作为辣椒疫霉对氟吡菌胺的敏感性基线。采用药剂驯化和紫外照射对辣椒疫霉敏感菌株TA进行诱变处理, 获得了2株辣椒疫霉抗氟吡菌胺菌株;利用菌落直径法测定抗氟吡菌胺菌株的遗传稳定性、菌丝生长速率及对其它杀菌剂的交互抗性;通过活体叶盘法测定抗氟吡菌胺菌株和敏感菌株的致病力及产孢子囊能力, 分析抗性和敏感菌株之间生物学特性差异。结果表明, 敏感菌株TA经过氟吡菌胺 48代连续汰选, 其抗性达58.0倍, 获得中抗菌株TA-R;紫外照射获得了抗性达260.6倍的高抗菌株TA-UV, 且其抗性均能稳定遗传;TA-R和TA-UV对甲霜灵、霜脲氰表现出正交互抗性, 对烯酰吗啉、百菌清、代森锰锌和丙森锌无交互抗性;抗氟吡菌胺菌株TA-R、TA-UV与敏感菌株在活体叶盘上的致病力、离体产孢能力均差异不显著(P＜0.05), 但其菌丝生长速率、菌丝干重均低于敏感菌株。     

Control of late blight in potato by full and reduced rates of oxadixyl mixtures

The effect of oxadixyl-based fungicidal mixtures on the development of late blight and the buildup of resistance ofPhytophthora infestans to oxadixyl was studied in potato crops (cv. Alpha) grown in plastic houses. Half-rates of SAN 518F (mancozeb + oxadixyl) applied weekly provided better disease control and reduced resistance buildup more effectively than the full rates of the mixture applied biweekly. Mancozeb applied weekly at full rate was less effective than SAN 518F at half-rate. The data suggest that lowering the dosage together with shortening the interval between sprays is an efficient strategy to combat mixed populations — sensitive and resistant to phenylamides — ofP. infestans when phenylamide-based fungicidal sprays are used.     

1,2-苯二硫酚衍生-高效液相色谱法检测二硫代氨基甲酸酯类化合物的方法改进

通过添加抗氧化剂四氢呋喃和抗坏血酸,对传统的二硫代氨基甲酸酯类化合物检测方法——1,2-苯二硫酚衍生-高效液相色谱法进行了优化和改进,并用4种常用二硫代氨基甲酸酯类杀菌剂[70%代森锰锌可湿性粉剂(WP)、68%精甲霜锰锌水分散粒剂(WG)、68%霜脲锰锌WG和55%唑醚代森联WG]对该方法进行了验证。结果表明:当1,2-苯二硫酚浓度为12 mmol/L、代森锰锌用乙二胺四乙酸二钠(EDTA,p H 9.3)及代森联用二乙基三胺五乙酸(DTPA,p H 10.0)解络合、且同时添加体积分数为4%的四氢呋喃和40 mg/L的抗坏血酸时衍生化条件最优。除55%唑醚代森联WG外,其他3种商品杀菌剂待测液在衍生化后48 h内均保持稳定且相对标准偏差5%,满足测试要求。该方法操作简便快捷,检出目标物明确,不受二硫代氨基甲酸酯类杀菌剂常见代谢物乙撑硫脲及二硫化碳的影响,检测效率高,适用于该类杀菌剂的批量测试。