Biological Mode of Action of Dimethomorph on Pseudoperonospora cubensis and Its Systemic Activity in Cucumber

Dimethomorph is a fungicide with high activity against Peronosporomycetes plant pathogens. The present study showed that dimethomorph is effective on controlling the oomycete fungal pathogen Pseudoperonospora cubensis causing downy mildew on cucumber. The fungicide did not affect zoospores discharge from sporangia of P. cubensis, but it strongly inhibited mycelial growth and sporangial production in vitro and increased lysis of zoospores. Dose of 2 mg L^-1 of dimethomorph was sufficient to inhibit mycelial growth and sporangial production of P. cubensis on leaf disks, 5 mg L^-1 was enough to lyse zoospores of P. cubensis, and 25 mg L^-1 was required to inhibit sporangial production on detached leaves. In whole plant tests, dimethomorph exhibited strong protective and curative activity. Dimethomorph when applied at a dose of 300 mg L^-1 for 1, 3, 5, 7 days before inoculation exhibited 100% efficacy on disease control. On the other hand, efficacies of 67.1 and 31.5% were obtained when the same dose of dimethomorph was applied for 1 and 3 days after inoculation, respectively. So dimethomorph had persistence effect on leaves for 7 days at least and exhibited strong protective and curative activity. Bioassay analyses showed that dimethomorph could be translocated in the xylem system, redistributed in the leaf, and penetrated from the upper surface to the lower surface of the leaf but could not be translocated in phloem system or transferred from the roots to leaves of cucumber plants in sufficient amounts for disease control. The biocharacteristics of dimethomorph make it well suitable for integration of a control programme against downy mildew disease on cucumber and as a component to delay other peronosporomycetes fungicide-resistance development.

Induction and Characterization of Laboratory Mutants of Phytophthora capsici Resistant to Dimethomorph and Flumorph

Laboratory studies were conducted to evaluate the risk of Phytophthora capsici developing resistance to two morphlines, dimethomorph and flumorph. Metalaxyl, the well-known high risk of resistance fungicides, was used as reference fungicide. Resistant mutants for the three fungicides were isolated by treating mycelium with ultraviolet radiation. Metalaxyl-resistant mutants were obtained with high frequency and exhibited high level of resistance with factors more than 100 folds, while mutation frequency for dimethomorph-resistance was relatively low and the resistance factors ranged from 3.0 to 13.9 folds. Most dimethomorph-resistant mutants decreased in hyphal growth rate and the spoulation ability, which have a large impact upon the epidemic development of dimethomorph-resistant populations. These results suggested that the risk of resistant pathogen population was much lower for dimethomorph than for metalaxyl. Both the frequency of developing resistance and level of resistance （resistance factors = 1.8-14.6） to dimethomorph were similar to those of its structure analogue flumorh. Moreover, the cross-resistance were found between them, which suggested the risks of developing resistance to dimethomorph and flumorph in the pathogen were very closely related. As P. capsici can potentially develop resistance to dimethomorph and flumorph, and oomycetes usually have the high risk to develop resistance to fungicides, appropriate management against resistance development should be taken.

Sensitivities of Phytophthora infestans to Metalaxyl, Cymoxanil, and Dimethomorph

The isolates of Phytophthora infestans on tomato in the Guangxi Zhuang Autonomous Region, China, were determined for the sensitivities to metalaxyl, cymoxanil and dimethomorph to give the basic information for integrating disease management. Sensitivities were tested by measuring the radial growth on agar medium amended with fungicide, compared with the floating-leaf-disk method. 239 isolates were collected from eight tomato growing areas during 2000-2006. The testing results indicated that the frequencies of sensitive, intermediate, and resistant isolates to metalaxyl were 42.26, 35.98, and 23.53%, respectively. Variations in sensitivities amongst isolates from different areas or different years were very high for metalaxyl. All isolates from Tianlin and Wuxuan were sensitive to metalaxyl, but the metalaxyl-resistant isolates predominated in Tianyang, with the frequency of 51.35%. The EC50 values of certain isolates from Tianyang were higher than 500 μg·mL^-1 and their resistance levels were over 100 000 folds. Cymoxanil has been used for nearly 10 years in Guangxi, and dimethomorph has been used for 5-6 years. However, there was no decrease in sensitivity of P. infestans populations and the sensitivities of the pathogen were nearly normally distributed. Hence, their mean ECs0 value [cymoxanil （0.1647 ±0.0255） μg·mL^-1, dimethomorph （0.0970 ± 0.0052） μg·mL^-1 could be used as the baseline sensitivities for monitoring the field resistance development. The comparison with the floating-leaf-disk method indicates that both the techniques provided equivalent results. These studies suggested that metalaxyl can be continuously applied in Tianlin, Wuxuan, and Nanning due to the resistant isolates that have not been found, while for those areas with resistant isolate, the use of metalaxyl should be reduced or alternated, and cymoxanil or dimethomorph was recommended for controlling late blight disease of tomato.

Photocatalytic degradation of dimethomorph on nanometer titanium dioxide by silver depositing in aqueous suspension

A series of catalysts of nanometer TiO2 were prepared by silver depositing. The photocatalytic degradation of dimethomorph in an aqueous suspensions by silver depositing with nanometer titanium dioxide as catalyst was investigated by radiation of UV-light and sunlight. A pseudo-first-order kinetic model was used to describe the results. The effects of the dosage of catalyst, oxidant, pH and radiation source on degradation were examined. The experimental results show that the decomposed rate of DMM is 94% when the dosage of catalyst is 1.25g/L and the concentration of DMM is 100mg/L under the conditions of solution pH of 7, the air flow of 1.5L/min and shining for 5h by UV-light. When it is shined by sun-light under the same condition, the decomposed rate of DMM is 48%. The mechanism of decomposition was discussed based on the data by analysis of LC-MS.

关于绿色食品青菜农药残留限量标准的探讨

在绿色认证的部分叶类蔬菜的监管过程中,发现部分农药的残留限量超过绿色标准的频次过高。通过解读绿色食品允许使用农药清单入选原则和绿色食品农药残留指标制定方法,分析了绿色产品青菜因质量抽检不合格撤销认证的原因。在对《绿色食品白菜类蔬菜》(NY∕T 654—2020)和《绿色食品绿叶类蔬菜》(NY∕T 743—2020)进行比对和梳理后,发现现行绿色标准对青菜农药残留的分类归属存在偏差和部分限量值过于严苛,无法满足生产和监管实际需求。建议将以上2个标准合并重修订为《绿色食品叶类蔬菜》,对于绿色农药清单中的农药种类应包含至少2种以上均能防治同一作物同一病虫害的可选农药,以满足生产农药交替使用的需求。

高效烯酰吗啉的制备和应用

以邻苯二酚为起始原料,在优化的反应条件下合成了烯酰吗啉,再利用烯酰吗啉不同异构体在相同溶剂中的溶解度差异,对(Z)-异构体和(E)-异构体进行分离,得到高效烯酰吗啉((Z)-异构体),并对分离出的低效体(E)-异构体进行了消旋和循环分离。采用菌丝生长速率法测定了烯酰吗啉、高效烯酰吗啉、烯酰吗啉(E)-异构体对辣椒疫霉菌的活性。结果显示,高效烯酰吗啉对辣椒疫霉菌具有较强的抑制作用。高效烯酰吗啉具有开发应用价值。

食用农产品中烯酰吗啉检测技术研究进展

烯酰吗啉是我国目前普遍使用的杀菌剂之一,对食用农产品中真菌引起的病害具有显著的防治效果。本文总结了食用农产品中烯酰吗啉的液相色谱-质谱联用法、高效液相色谱法、气相色谱法、酶联免疫法和胶体金免疫层析法等检测方法,为烯酰吗啉的检测和新检测方法的开发提供参考依据。

Study on anti-pollution nano-preparation of dimethomorph and its performance

The photocatalysis of nanometer TiO2/Ag was modi- fied by sodium dodecyl sulfate,and its behavior of adsorption for pesticide was investigated on the surface of catalyst.Four kinds of water-olubility preparations were prepared by using TiO2/Ag,modified TiO2/Ag by 0.5% SDS,TiO2 and nothingness as photocatalyst with dimethomorph as effective compo- nent.They were besmeared on a piece of glass,and the photocatalytic experiment was done in sunlight.Degradation rates of 1.2% di- methomorph are 71.5%,68.0%,45.5% and 28.3%,respectively,when it was degraded in five days.Degradation rate of 10% dimetho- morph is 97.3% in eight days in sunlight and t1/2 is 2.8 d in nano-preparation,when it was sprayed on small cabbages after being diluted in rudimental experiments of toxicity for crop.The nano-preparation is of better biologic activity,the virulence of which is 1.235 times as great as original pesticide and 1.245 times as ordinary preparation under the same con- dition.

致病疫霉对烯酰吗啉和双炔酰菌胺的敏感性动态监测及马铃薯晚疫病田间防治药剂筛选

为明确马铃薯北方一季作区致病疫霉对烯酰吗啉和双炔酰菌胺的敏感性时空动态及常用药剂对马铃薯晚疫病的田间防效,采用菌丝生长速率法测定了2011—2019年采自河北、内蒙古和吉林3省(区)马铃薯主产区的922个致病疫霉菌株对烯酰吗啉和双炔酰菌胺的敏感性,采用茎叶喷雾法于2018年和2019年评估了烯酰吗啉和双炔酰菌胺等7种杀菌剂在推荐剂量下对马铃薯晚疫病的田间防效。结果表明:在时间上,不同年份采集的922株致病疫霉对烯酰吗啉的抗性频率和抗性指数分别为25.71%~100%和0.31~0.50;890株致病疫霉对双炔酰菌胺的抗性频率为0~1.43%,仅于2013年检测到抗性菌株,历年抗性指数均为0.25。在地域上,3省(区)致病疫霉菌株对烯酰吗啉的抗性频率和抗性指数分别为57.19%~66.56%和0.39~0.42;对双炔酰菌胺的抗性频率为0~0.36%,抗性指数均为0.25。田间药效试验结果显示:50%烯酰吗啉可湿性粉剂(有效成分,下同) 300.0 g/hm^(2)对马铃薯晚疫病的防治效果(83.3%~85.6%)高于23.4%双炔酰菌胺悬浮剂140.4 g/hm^(2)的防治效果(76.9%~78.6%)和50%氟醚菌酰胺水分散粒剂75.0 g/hm^(2)的防治效果(70.0%~71.4%)。20%霜脲氰悬浮剂162.0 g/hm^(2)、40%氟醚菌酰胺·烯酰吗啉悬浮剂240.0 g/hm^(2)、43%霜脲氰·双炔酰菌胺水分散粒剂290.3 g/hm^(2)和687.5 g/L氟吡菌胺·霜霉威盐酸盐悬浮剂773.4 g/hm^(2)对马铃薯晚疫病的防治效果为79.8%~86.9%。为此,推荐烯酰吗啉单剂或混剂及双炔酰菌胺混剂在河北、内蒙古和吉林3省(区)继续用于马铃薯晚疫病的防治,但是需密切监测致病疫霉对烯酰吗啉和双炔酰菌胺的敏感性变化并注意与不同作用机理的杀菌剂混用或者交替使用。

彩椒中克百威和烯酰吗啉残留量测定盲样考核及结果分析

目的:通过参加2021年国家级食品安全风险监测彩椒粉中农药残留质量考核,证实并提高检测实验室的农药残留测定能力。方法:样品经乙腈提取净化后取上清液过膜上样,高效液相色谱质谱联用法测定,采用基质曲线内标法定量。结果:彩椒中克百威和烯酰吗啉残留量的测定结果分别为0.54 mg·kg^(-1)、6.44 mg·kg^(-1),盲样真值分别为0.62 mg·kg^(-1)、6.39 mg·kg^(-1),回收率分别为87.1%、100.8%。结论:盲样考核结果满意,本实验室的农药残留检测能力很好。

中国4省份葡萄霜霉病菌群体对烯酰吗啉的抗性及适合度

为明确我国山西、山东、河北和云南省葡萄霜霉病菌对烯酰吗啉的抗性以及田间病菌群体的适合度,本研究采用Taqman-MGB技术检测了2020年-2021年采自上述4省份292株葡萄霜霉病菌对烯酰吗啉的抗性频率;采用叶盘法测定了田间抗性菌株与敏感菌株的适合度。结果表明,上述4个地区的平均烯酰吗啉抗性频率及抗性等位基因频率分别为64.0%和74.7%,其中山东省蓬莱区最高(91.2%和96.3%),河北省廊坊市(73.8%和85.0%)和云南省宾川县(75.0%和82.6%)次之,山西省清徐县(16.7%和34.7%)最低。适合度分析发现,田间抗性菌株的产孢能力明显高于敏感菌株,但二者的复合适合度指数无显著差异。上述结果表明,4省份霜霉病菌群体均对烯酰吗啉产生了不同程度的抗性,田间抗性菌株与敏感菌株相比无明显适合度变化。

荔枝霜疫霉对烯酰吗啉的抗性风险评估

【目的】检测荔枝霜疫霉对烯酰吗啉的敏感性,建立敏感性基线;测定抗烯酰吗啉突变株的生物学适合度,为荔枝霜疫病的化学防治提供依据。【方法】采用菌丝生长速率法,对2019—2020年来自中国广东、广西、福建、四川和云南5个省份荔枝主产区的320株荔枝霜疫霉单孢子囊菌株进行烯酰吗啉敏感性测定,通过药剂驯化获得抗烯酰吗啉突变株,测定其生物学适合度。【结果】经过异常值分析并剔除,317株荔枝霜疫霉菌株对烯酰吗啉的敏感性频率分布呈正态分布,EC_(50)值介于0.0863~0.1733μg·mL^(-1)之间,平均(0.1222±0.0009)μg·mL^(-1),以此建立荔枝霜疫霉对烯酰吗啉的敏感性基线。来自2020年的荔枝霜疫霉菌株对烯酰吗啉的EC_(50)均值较2019年显著增高。3株荔枝霜疫霉抗烯酰吗啉突变株的抗性指数介于77.17~360.11之间,为中到高抗水平,抗药性可稳定遗传,与亲本相比,抗性突变株的孢子囊萌发率及卵孢子产量均下降,但致病力相当。【结论】荔枝霜疫霉对烯酰吗啉敏感,烯酰吗啉可继续作为防治荔枝霜疫病的有效杀菌剂。

腐霉利和烯酰吗啉在甘肃省平凉市设施番茄中膳食暴露风险评估

甘肃省平凉市农产品质检中心承担的2017—2021年5年市级例行监测任务中使用气相色谱-质谱联用法、液相色谱-串联质谱法测定58种农药。检测数据发现,232份设施番茄样品中腐霉利和烯酰吗啉农药残留合格率均为100%,但检出率分别21.55%和6.03%,相对其他农药检出率比较高;在检出腐霉利农药中有54%残留量分布在0.02~0.22 mg/kg范围,检出烯酰吗啉农药中有79%残留量分布在0.0001~0.1001 mg/kg范围,检出残留量相对比较集中,且2种农药的最高检出值均低于该农药最大残留限量值(MRL)。结果显示:腐霉利和烯酰吗啉慢性膳食摄入风险分别为1.21%和0.165%,均远小于100%。急性膳食摄入风险分别为8.06%和0.291%,远小于100%,急性和慢性风险均在可接受范围内;腐霉利和烯酰吗啉的风险得分分别为10.43和10.12,残留风险相对比较低,处于低风险水平。

杀菌剂烯酰吗啉的合成研究进展及应用

烯酰吗啉属于吗啉类广谱性杀菌剂,是一种新型内吸治疗性专用低毒杀菌剂。文章综述了烯酰吗啉的合成路线,分析比较了以吗啉、邻苯二酚、乙酰吗啉为起始原料制备的合成路线,评述了制备方法的优势与不足,为烯酰吗啉的绿色生产及工业化提供思路。同时介绍了有关烯酰吗啉配伍使用的应用研究动态,为开发下游高附加值产品提供参考。

马铃薯晚疫病菌在内蒙古和甘肃的交配型分布及对几种杀菌剂的敏感性

1997— 2 0 0 1年在内蒙古自治区和甘肃省马铃薯主产区采集马铃薯晚疫病菌并进行了交配型和药剂敏感性测定。结果为 :采自内蒙古的 14 3株菌中有 14 0株是典型A1交配型、3株是可自育的A1交配型 ;采自甘肃的 4 1株菌中有 4 0株是典型A1交配型、1株为可自育的A1交配型 ;二省都未发现A2交配型。表明内蒙古和甘肃马铃薯主产区的晚疫病菌以A1交配型占绝对优势。对甲霜灵 (metalaxyl)的敏感性测定显示 :内蒙古菌株中有 5 0 .8%表现高度抗性、4 2 .5 %表现中度抗性、只有 6 .7%表现敏感 ,说明内蒙古马铃薯主产区的晚疫病菌普遍对甲霜灵具有了抗性 ;甘肃的菌株中 ,2 6 8%表现高度抗性、2 9.3%表现中度抗性、4 3.9%表现敏感 ;同时发现甲霜灵可刺激某些抗性菌株的生长。试验还测定了 35株菌对烯酰吗啉 (dimethomorph)和腈嘧菌脂 (azoxystrobin)的敏感性 :其中对烯酰吗啉表现敏感的占 94 %、中度敏感的占 6 % ;对腈嘧菌脂敏感的占 71.4 % ,中度敏感的占 2 8.6 % ;未发现对二种药剂高抗或不敏感菌株 ,且烯酰吗啉和腈嘧菌脂与甲霜灵均无交互抗性。

番茄晚疫病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性检测

【目的】研究广西番茄晚疫病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性,以期为该病的综合治理提供科学依据。【方法】用菌落生长直径法测定病菌对甲霜灵、霜脲氰和烯酰吗啉的敏感性,并用叶盘漂浮法加以比较。【结果】2000～2006年,从广西8个冬春植番茄区采集分离了239个菌株,测定结果表明,对甲霜灵表现为敏感型、中间型和抗性型的频率分别为42.26%、35.98%和23.53%,不同地区和年份的菌株对甲霜灵的敏感性差异很大。来自田林县、武宣县的菌株均为甲霜灵敏感性菌株,但在田阳县,抗甲霜灵菌株占优势,抗性频率高达51.35%,一些菌株的EC50值在500μg·ml-1以上,抗性水平超过105倍。虽然霜脲氰在广西使用了近10年,烯酰吗啉也已应用了5～6年,但并未检测到番茄晚疫病菌对它们的敏感性下降的抗药性亚群体,病菌的敏感性接近正态分布,因此可以采用它们的平均EC50值(霜脲氰0.1647±0.0255μg·ml-1,烯酰吗啉0.0970±0.0052μg·ml-1)作为抗药性监测的敏感性基线。叶盘漂浮法测定结果与菌落生长直径法一致。【结论】广西田林县、武宣县和南宁市番茄晚疫病菌尚未出现抗甲霜灵菌株,仍可用甲霜灵来防治该病,而其它地区则应减少或不使用甲霜灵,改用霜脲氰或烯酰吗啉。

马铃薯晚疫病菌对烯酰吗啉的敏感性基线及其室内抗药突变体的研究

2003-2004年在内蒙古和黑龙江省共分离获得100株马铃薯晚疫病菌,并测定了这些菌株对烯酰吗啉和甲霜灵的 敏感性。结果表明,不同地区、不同年份的马铃薯晚疫病菌对烯酰吗啉的敏感性无显著差异,其敏感性呈连续的单峰曲线 分布,EC50在0．0631-0．2206μg/mL之间,最不敏感菌株是最敏感菌株的3．1倍,平均为(0．1153±0．0308)μg／mL,未 出现敏感性下降的抗药性亚群体,因此可作为马铃薯晚疫病菌对烯酰吗啉的敏感性基线;64％的供试菌株对甲霜灵的敏感 性下降,甲霜灵与烯酰吗啉之间不存在交互抗药性。采用紫外线诱变菌丝的方法仅从3个菌株中的1个菌株获得了3％突 变频率的抗烯酰吗啉突变体,抗性倍数为1．5-1．9,没有获得高抗药水平的突变体。这些突变体与氟吗啉之间具有正交互 抗药性,而与霜脲氰或嘧菌酯之间无交互抗药性;与野生亲本菌株相比,抗药突变体的生长速率和产孢子囊能力显著下降, 不利于抗药群体的发展。但由于马铃薯晚疫病菌被杀菌剂抗性行动委员会认为是高抗药性风险病原菌,建议生产上应将 烯酰吗啉与其它无交互抗性的药剂交替使用或混合使用,以避免或延缓抗药性的产生。

烯酰吗啉对我国烟草黑胫病菌的毒力研究

从山东和云南烟区采集分离了20个烟草黑胫病菌phytophthora parasitica vat．nicotianae菌株，采用菌丝生长速率法测定了烯酰吗啉对这些菌株的毒力。结果表明：20个田间菌株的EC50值在0．60-1．28μg/mL之间，与实验室保存的敏感菌株（S）的EC50值（0．32μg/mL）相比，毒力倍数在1．87—4．00之间．均属于敏感菌株。烯酰吗啉对烟草黑胫病菌孢子囊的产生有明显的抑制作用，8．00μg/mL的烯酰吗啉对孢子囊产生的抑制率为100％。通过烯酰吗啉对烟草黑胫病菌继代培养物的毒力比较证明，烟草黑胫病菌对烯酰吗啉存在抗性风险。

木质素磺酸盐在烯酰吗啉颗粒表面的吸附特性

考察了常用分散剂木质素磺酸钠(Sodium Lignosulfonate,SLS)在烯酰吗啉(Dimethomorph,DMM)上的吸附性能,并测试了吸附SLS后DMM颗粒表面Zeta电位和接触角的变化,从理论上探讨了分散剂的吸附对农药颗粒表面物化性能的影响,指导农药分散剂的开发.结果显示,浓度为0～10 g/L时,SLS在DMM表面呈现双层吸附;低浓度(0～1.0 g/L)时,吸附等温线符合Langmuir方程.SLS在DMM表面上的吸附属于自发、放热吸附过程,吸附力主要包括疏水作用、范德华力和氢键作用力.SLS在DMM表面吸附后提高了其Zeta电位,且SLS磺化度越高其提高作用越明显.随着SLS溶液浓度增大,DMM在SLS溶液中的接触角先减小后增大,到70°～80°后趋于稳定.

三种羧酸酰胺类杀菌剂对黄瓜疫霉菌不同发育阶段的影响及其敏感性测定

离体条件下测定了3种羧酸酰胺类(Carboxylic acid amides,CAAs)杀菌剂氟吗啉、烯酰吗啉和异丙菌胺对黄瓜疫霉菌不同生长发育阶段的抑制作用。结果表明,3种杀菌剂抑制黄瓜疫霉菌休止孢萌发的EC50值分别为0.54,0.46和0.34μg/mL;抑制菌丝生长的EC50值分别为0.92,0.70和0.67μg/mL;抑制孢子囊形成的EC50值分别为0.48,0.31和0.26μg/mL。但对游动孢子的释放、游动及休止孢的形成均没有抑制作用。氟吗啉、烯酰吗啉和异丙菌胺抑制田间采集的供试菌株菌丝生长的平均EC50值分别为1.09(±0.24),0.29(±0.04)和0.32(±0.07)μg/mL,供试菌株对3种杀菌剂的敏感性均呈正态分布,未检测到抗药性菌株的存在。