Benzimidazole resistance in Pseudocercosporella herpotrichoides: results of ADAS random surveys and fungicide trials in England and Wales, 1982–19841

Surveys of 59 and 528 randomly selected winter wheat and winter barley crops in 1982 and 1983 respectively, showed that benzimidazole-resistant strains of the eyespot fungus (Pseudocercosporella herpotrichoides) were common and widespread. The frequency of occurrence of resistant isolates, both in 1982 and 1983. was positively correlated with the number of benzimidazole fungicide applications since 1975. Resistance was much more frequent in R-type than in W-type strains of P. herpotrichoides. Fungicides or fungicide mixtures, applied to winter wheat at growth stage (GS) 31, were compared for control of eyespot at six sites in 1983 and one in 1984 where benzimidazole-resistant strains were readily detected prior to spraying. Carbendazim alone gave no control of eyespot and in some trials actually increased disease levels compared with the unsprayed control. Prochloraz, either alone or in mixture with carbendazim, was the most effective fungicide giving a moderate control of eyespot (33–42% reduction) and cost-effective yield increases. DPX-II6573, tested only in the 1984 trial, was as effective as prochloraz. The practical implications of these findings are discussed.     

Development of apothecia ofTapesia yallundae in contrasting populations selected by fungicides

Apothecia of the eyespot fungus,Tapesia yallundae, were found on 0–18% of straws in plots of wheat stubble in February–March 1994. The fungicides carbendazim, prochloraz or carbendazim plus prochloraz had been applied repeatedly to the same plots in each of the previous 9 years in which successive wheat crops had been grown. The factors most strongly correlated with the incidence of apothecia were the incidence and severity of eyespot in the preceding wheat crop and the frequency of carbendazim-resistant W-type fungus in populations recovered from that wheat crop. Plots treated with carbendazim, which had previously had more disease and more resistance to carbendazim in the pathogen population relative to untreated plots, therefore yielded most apothecia. Plots treated with prochloraz, which had selected for predominantly R-type fungus and decreased eyespot, yielded few apothecia. Single-ascospore isolates were all of the W-type and were more frequently carbendazim-sensitive than expected, except those from plots treated only with carbendazim. None showed decreased sensitivity to prochloraz. The implications of applying fungicides regularly for controlling eyespot on the capability of the eyespot fungus for genetic variation through sexual reproduction are discussed.     

Changes in fungicide sensitivity and relative species abundance in Oculimacula yallundae and O. acuformis populations (eyespot disease of cereals) in Western Europe

Changing fungicide sensitivities in populations of Oculimacula yallundae and O. acuformis , the species responsible for cereal eyespot in Western Europe, were determined over a 17 year period between 1984 and 2000. The data were collected by Aventis Crop Science as part of their long-term survey to monitor changes in sensitivity to prochloraz and the methyl benzimidazole carbamate (MBC) fungicides in eyespot populations. The results show evidence for reduced sensitivity to both fungicides over the period of the survey. The decline in MBC sensitivity is in agreement with reports of practical resistance (a detectable loss of disease control in the field) to this fungicide which were widely reported from the mid 1980s onward. Prochloraz sensitivity was more complex, with the emergence of a higher resistance category of isolates in the late 1980s and early 1990s which then decreased in frequency towards the end of the survey. This may be partly explained by the introduction and increased use of cyprodinil in the mid 1990s. Although all trends were similar across Europe, differences were observed between the two eyespot species. A higher frequency of O. yallundae isolates showed decreased sensitivity to MBC, whereas decreased sensitivity to prochloraz was at a higher frequency in O. acuformis populations. The relative abundance of the two eyespot species was influenced by their differential levels of fungicide sensitivity, with the ratio increasing toward the species with the highest level of resistance to the prevailing fungicide.     

Influence of spray programmes on development of fungicide resistance in the eyespot pathogen of wheat, Pseudocercospovella herpotrichoides

A site with no known history of cereal growing or carbendazim fungicide use was inoculated in 1983 with an equal mixture of spores of R-type and W-type isolates of Pseudocercosporella herpotrichoides. all sensitive to carbendazim. Following three consecutive years of carbendazim sprays, more than 90% of isolates recovered were carbendazim-resistant. A majority of R-type isolates was recovered after 3 years and resistance was found to be more frequent in R-type than in W-type isolates. A mixture of carbendazim with prochloraz initially delayed the development of carbendazim resistance, but after 3 years the incidence of resistance was similar to that where carbendazim alone was applied. The best control of eyespot was given by the mixture and by a split application of prochloraz in the first year, by the mixture in the second year, and by the split prochloraz application in the final year. A greater proportion of R-type isolates was recovered from prochloraz-treated plots than from unsprayed plots; the proportion of these that were resistant to carbendazim was lower than that from carbendazim treatments. Throughout this study isolates resistant to prochloraz were not detected.     

3种新型生物产品及复配杀菌剂防治 小麦赤霉病的研究

为筛选防治小麦赤霉病的新型生物产品及其减药增效配方, 于2016年分别在湖北襄阳和荆州开展田间试验?评价了植物免疫蛋白质生物农药6%寡糖·链蛋白可湿性粉剂?诱抗剂0.5%大黄素甲醚水剂和生物刺激素爱诺森可溶液剂对赤霉病的防治效果, 筛选了上述3种生物产品与常规化学农药430 g/L戊唑醇悬浮剂?25%咪鲜胺乳油和50%多菌灵可湿性粉剂减药增效组合配方?结果表明:6%寡糖·链蛋白可湿性粉剂和0.5%大黄素甲醚水剂处理的防效分别在20.18%~24.37%和18.32%~22.98%之间, 爱诺森处理对小麦赤霉病无防治效果?430 g/L戊唑醇悬浮剂?25%咪鲜胺乳油和50%多菌灵可湿性粉剂等3种杀菌剂减量20%分别与寡糖·链蛋白?大黄素甲醚和爱诺森复配田间防效表明, 50%多菌灵可湿性粉剂减量20%与寡糖·链蛋白?大黄素甲醚和爱诺森3种生物产品复配处理的病情指数在3.34~7.81, 防治效果在63.99%~77.56%, 其增效范围在3.22%~47.59%, 与430 g/L戊唑醇悬浮剂未减药用量的防效相当( P >0.05)?50%多菌灵可湿性粉剂减量20%与寡糖·链蛋白?大黄素甲醚和爱诺森3种生物产品复配处理的产量显著高于未减药的多菌灵处理产量( P <0.05), 增产幅度在3.74%~9.28%之间?30 g/L戊唑醇悬浮剂和25%咪鲜胺乳油减量20%与寡糖·链蛋白?大黄素甲醚和爱诺森3种生物产品复配处理的防效和增产效果趋势不显著?     

稻田土壤8种真菌对4种杀菌剂的敏感性分析

基于ITS-5.8s rDNA区序列,初步鉴定了浙江大学试验基地稻田土壤的8种常见真菌。采用菌丝生长速率法测定了井冈霉素、多菌灵、咪鲜胺和三唑酮4种常用杀菌剂对这8种土壤真菌的抑菌活性,以及多菌灵与咪鲜胺混用对禾柄锈菌、黑曲霉和长枝木霉3种真菌菌丝生长的抑制作用。结果表明:8种真菌对咪鲜胺最敏感,EC50值在0.091~3.1 mg/L之间;多菌灵的EC50值在0.15~1.8 mg/L之间;三唑酮的EC50值在0.57~8.5 mg/L之间;井冈霉素的敏感性最低,EC50在12~94 mg/L之间。由4种杀菌剂的SSDs曲线分析结果得出,不同真菌对杀菌剂敏感性存在显著差异。当多菌灵与咪鲜胺按其EC50值分别以体积比3∶2、1∶1和7∶3混用时,增效系数分别为1.615、1.039和1.042,表现出一定的协同或相加作用。本研究结果为进一步阐明杀菌剂对稻田生态系统真菌群落的生态效应及杀菌剂的科学合理使用提供了重要依据。     

水稻恶苗病菌田间抗咪鲜胺菌株的适合度及其交互抗性

恶苗病是水稻生产上较为严重的种传真菌病害,咪唑类广谱内吸性杀菌剂咪鲜胺是目前防治该病害的主要药剂。以对咪鲜胺抗性及敏感的田间水稻恶苗病菌为试材,研究了其适合度及对几种常用杀菌剂的交互抗性。结果显示:抗性菌株的抗药性可稳定遗传,其温度敏感性与敏感菌株无明显差异,部分抗性菌株在菌丝生长速率、产孢量、孢子萌发率和致病力方面显著高于田间敏感菌株;咪鲜胺与三唑类及2-氰基丙烯酸酯类杀菌剂之间均无交互抗性。研究表明,对咪鲜胺产生抗性的水稻恶苗病菌具有较强的适合度,在田间自然条件下有可能形成优势群体,因此需合理轮换使用不同作用机制的杀菌剂,以延缓其抗药性的发展。     

啶酰菌胺等8种杀菌剂对烟草叶斑病菌的生物活性

采用生物测定方法分析了烟草叶斑病菌Didymella segeticola在菌丝生长阶段对8种杀菌剂(啶酰菌胺、苯醚甲环唑、丙环唑、氟硅唑、多菌灵、咪鲜胺、菌核净和代森锰锌)的敏感性,同时通过离体叶片法测定了8种杀菌剂对烟草叶斑病的保护和治疗作用。结果表明：供试8种杀菌剂对D. segeticola菌丝生长表现出不同的抑制活性,同时对其引起的病害具有一定的保护和治疗作用。抑菌活性最强的是啶酰菌胺,其平均EC₅₀值为(0.047 0±0.012 0) mg/L;其次依次为苯醚甲环唑[(0.079 0±0.005 0) mg/L]、咪鲜胺[(0.29±0.08) mg/L]、丙环唑[(0.69±0.12) mg/L]、菌核净[(1.08±0.33) mg/L]、多菌灵[(1.22±0.29) mg/L]、氟硅唑[(1.38±0.07)mg/L];代森锰锌的抑菌活性最弱[(22.80±10.51) mg/L]。进一步研究表明,氟硅唑、苯醚甲环唑、丙环唑、啶酰菌胺、菌核净和多菌灵对烟草叶斑病保护作用较强,25 mg/L药剂质量浓度处理下防效均>82%;100 mg/...     

湖北省小麦赤霉病菌对多菌灵、戊唑醇和咪鲜胺的敏感性

对2014年采自中国湖北省7个县、市的206株小麦赤霉病菌样品进行单孢分离与鉴定,并采用菌丝生长速率法随机测定了其中100株菌株对多菌灵、戊唑醇和咪鲜胺的敏感性,建立了其敏感基线。结果表明:多菌灵、戊唑醇和咪鲜胺对湖北省小麦赤霉病菌的EC50值范围分别为0.115~0.705、0.006~1.356和0.002~0.370 μg/mL,平均值分别为0.248、0.181和0.040 μg/mL;供试100株小麦赤霉病菌对3种药剂的敏感性频率均呈单峰拟正态分布,因此可将所得各EC50平均值分别作为湖北省小麦赤霉病菌对3种药剂的敏感基线参考值。以各药剂EC50平均值的10倍作为敏感性鉴别浓度,对2015及2016年湖北省小麦赤霉病菌的敏感性进行了监测,在该鉴别浓度下,多菌灵、戊唑醇和咪鲜胺对2015年小麦赤霉病菌的平均抑制率分别为100%、85.14%和82.35%,对2016年小麦赤霉病菌的平均抑制率分别为100%、76.67%和73.62%。研究表明,虽然戊唑醇和咪鲜胺对2016年小麦赤霉病菌的抑制率略有下降,但整体而言,湖北省小麦赤霉病菌对多菌灵、戊唑醇及咪鲜胺仍具有较高的敏感性。     

不同杀菌剂对小麦赤霉病和叶锈病的防治效果

为明确不同杀菌剂防治小麦赤霉病和叶锈病的效果,在大田条件下进行了不同杀菌剂对这两种病害的防治试验.对小麦赤霉病的防效结果表明:25％氰烯菌酯SC、20％叶菌唑SC、48％氰烯·戊唑醇SC和200 g/L氟唑菌酰羟胺SC的防效较好,防效为83.54％～88.92％;其次为400 g/L戊唑·咪鲜胺EW和430 g/L戊唑...     

不同杀菌剂对番石榴枝枯病病原菌的毒力和田间防效

为有效防治我国近些年新发现的番石榴枝枯病,本研究采用菌丝生长速率法和孢子萌发法,测定了8种杀菌剂对番石榴枝枯病菌(小新壳梭孢)的毒力,筛选出高效药剂,并进行田间防治试验。结果表明:30%咪鲜胺CS对小新壳梭孢的抑菌能力最强,EC_(50)为0.2 mg/L;其次是60%苯醚甲环唑WG和35%苯甲·嘧菌酯SC,EC_(50)分别为0.23和0.29 mg/L。30%咪鲜胺CS和35%苯甲·嘧菌酯SC对小新壳梭孢分生孢子萌发的抑制作用最强,EC_(50)分别为0.07和0.09 mg/L;30%咪鲜胺CS和60%苯醚甲环唑WG的预防作用和治疗作用效果也最好;田间试验结果表明,使用30%咪鲜胺CS和60%苯醚甲环唑WG防治番石榴枝枯病的防效最好,达到56.87%和52.40%,有较大的应用潜力。     

Unexpected Effects of Fungicides on Cereal Yields1

Field experiments with barley have generally shown a good relationship between disease and yield. However, in some experiments the yield response is greater than would be expected from the level of disease. In contrast, other trials have shown a reduction of yield following applications of tridemorph to spring barley. On winter wheat, trials in Germany have shown a poor relationship between disease incidence and yield following application of carbendazim or captafol at GS 30–31. About 10 96 of these responses were negative, although there was an average yield increase of 2–3 %. Similarly, in a series of trials in Britain an average yield increase of 3 % was not related to disease level. In these trials about 25 % of results showed no increase in yield. The carbendazim fungicides, and also certain others, have some cytokinin-like activity and it is possible that this is related to extended green leaf survival. Other interactions with host-cell chemistry can be envisaged. Fungicides also influence stability of the leaf microflora. By this effect they may favour diseases such as Typhula and Rhizoclonia, or else suppress secondary pathogens (Alternaria, Cladosporium) at the end of the season.     

水稻穗腐病病菌致病性、发生规律及防控技术研究

穗腐病是近年发生危害严重的水稻穗部病害.本研究对穗腐病的发生、流行原因进行了分析,分离了病原菌并测定了致病性,筛选了防治该病的杀菌剂并进行了田间防效试验.结果表明,紧穗型的粳稻及籼/粳杂交稻组合较穗型松散的籼稻及其杂交组合更易感病.水稻孕穗后期-抽穗扬花期遇阴雨高湿、温暖天气该病发生危害重.用分离到的4个菌(层出镰刀菌、澳大利亚平脐蠕孢菌、新月弯孢菌和细交链孢菌)进行人工接种,均能使稻粒感病,初步确定层出镰刀菌为主要初侵染菌.室内抑菌测试结果显示,5 mg/L以上浓度的多菌灵、咪鲜胺和苯醚甲环唑·丙环唑(爱苗)对层出镰刀菌生长的抑制效果达到81.31％～100％.抑制中浓度为0.000 7～0.947 6 mg/L.田间试验结果表明,在水稻孕穗后期和抽穗扬花期用三唑酮、多菌灵或甲基硫菌灵喷雾防治一次,防效在70％左右.     

五种杀菌剂胁迫下灰葡萄孢产孢所需碳源种类分析

灰葡萄孢是引起作物灰霉病的病原菌,分生孢子是其传播的主要载体.本文采用代谢技术分析了灰葡萄孢对Biolog FF板碳源的利用及其产孢情况,并测定了在多菌灵、丙环唑、嘧霉胺、异菌脲和咪鲜胺5种杀菌剂胁迫下灰葡萄孢产孢所需碳源种类.结果表明:糖类、氨基酸类等92种碳源均能被灰葡萄孢代谢,其中,杏仁苷、L-阿拉伯糖等35种碳...     

A mini-bag technique for evaluation of fungicide effects on Trichoderma spp in mushroom compost

An in vivo technique was developed to observe colonisation of mushroom compost by Trichoderma spp. Isolates of T. harzianum (Th2), T. harzianum (Th1), T. koningii (Tk) and T. viride (Tv) were artificially introduced into compost using a mini-bag system. Wheat grains, colonised by Trichoderma spp, were placed centrally on a layer of compost at the bottom of 1-litre polythene bags which were then filled with 350 g of spawned or un-spawned compost, and partially sealed. After 14 and 21 days incubation at 27 degrees C, the bags were assessed for recovery of Trichoderma from middle and top zones using a needle stab re-isolation technique and a visual colonisation scoring system. Visible green mould contamination, similar to that observed in practice, developed within 21 days. The visual colonisation scoring was reliably related to the re-isolation success. In this evaluation, Trichoderma spp showed considerable differences in their relative abilities to colonise spawned and un-spawned compost, with Th2 isolates being consistently superior to the other isolates of Th1, Tk and Tv in colonising spawned compost. This technique was employed to evaluate the effects of fungicides on the colonisation of mushroom compost by three Trichoderma spp: Th2, Th1 and Tk, using 1-litre and 5-litre mini-bag systems. Aqueous suspensions of benomyl, carbendazim, thiabendazole, prochloraz and prochloraz+carbendazim incorporated into the compost at 50 mg litre(-1), or applied to spawn at 50 mg kg(-1), reduced the colonisation by Trichoderma spp. Prochloraz and prochloraz+carbendazim were superior to benomyl, carbendazim or thiabendazole in reducing compost colonisation by Th2, Th1 and Tk, with Th2 being the most persistent type, capable of colonising treated compost in the presence of all five fungicides. The prochloraz+carbendazim mixture, not normally used in mushroom production, was equal to or better than prochloraz alone. The incidence of green mould colonisation by Th2 was as extensive in the 5-litre compost bags as in the 1-litre bags, but colonisation by Th1 and Tk was more apparent in the 5-litre bags. The in vivo mini-bag evaluations using wheat grain Trichoderma inoculum and needle stab re-isolation procedures proved an efficient method for studying colonisation and screening for effectiveness of fungicides applied to mushroom compost or spawn.     

嘧菌酯对扁豆纹枯病的物理作用方式及其生物动力学特性

以多菌灵和福美双为对照药剂,测定了嘧菌酯对立枯丝核菌Rhizoctonia solani的抑制活性,并用离体叶片法测定了嘧菌酯对该病原菌引起的扁豆纹枯病的物理作用方式及其生物动力学特性。嘧菌酯、多菌灵和福美双对立枯丝核菌菌丝生长的EC50值分别为0.072 4、1.134 4和1.202 6 μg/mL。施药后立即接种, 250 μg /mL嘧菌酯、500 μg /mL多菌灵和1 000 μg /mL福美双对扁豆纹枯病的保护效果分别为95.61％、99.88％和81.45％;施药3 d后再接种,嘧菌酯、多菌灵和福美双对扁豆纹枯病的保护效果分别为92.27％、100％和46.96％;接种36 h后再施药,3种药剂对扁豆纹枯病的治疗效果分别为90.40％、95.75％和61.94％。表明嘧菌酯对扁豆纹枯病具有很好的保护作用、持效性和治疗作用。在叶片基部施药后在顶部接种,嘧菌酯、多菌灵和福美双对扁豆纹枯病的防治效果分别为87.81％、42.09％和7.24％;在叶片背面施药后在正面接种,3种药剂对扁豆纹枯病的保护效果分别为87.30％、37.00％和16.15％。表明嘧菌酯在扁豆叶片中具有很好的木质部输导和跨层转移活性。     

Control of Glomerella cingulata f.sp. camelliae with fungicides

A critical test of fungicidal activity against the wound pathogen Glomerella cingulata f.sp. camelliae on camellias involved the application of a conidial suspension to scratches on detached leaves, treated with fungicide 24 h previously. In this test, prochloraz at 250–500 μg/ml a.i. in both EC and manganese WP formulations was highly effective, inhibiting leaf rotting by 90–100% compared with 55% or less in some tests with benomyl, chlorothalonil and captafol at 500–1000 μg/ml and captan at 1200 μg/ml. Prochloraz gave similar protection to leaves when applied to whole plants. Protection was less, especially on older leaves, when wounding and inoculating were delayed by 7 or more days after treatment. Prochloraz did not prevent all infection through comparatively large wounds, e.g. leaf scars, made on stems 24 h after treatment.
Poor control of the disease in a nursery was not due to resistance of the pathogen to benomyl; in vitro tests failed to detect full resistance at this time. Under nursery conditions a statutory policy of destroying infected plants and spraying the remainder with prochloraz or prochloraz manganese (both at 500 μg/ml), alternating with benomyl (500 μg/ml) on a weekly basis apparently prevented spread of the disease to healthy plants.     

Fungicide and nitrogen applications in relation to the improvement of disease control and yield in winter barley

In crops of winter barley, cvs Igri and Halcyon, crop structure and intensity of foliar diseases were altered by delaying the main top dressing of nitrogen until mid-April. A single application of fungicide then was sufficient to decrease substantially the severity of fungal disease and improve grain yield at harvest.
Disease control and yield responses were greatest when fungicides were applied during a 3-week period after the main nitrogen application in April. No additional yield benefits were obtained by making two fungicide applications at growth stage (GS) 31 and GS 39.     

Carbendazim resistance in the eyespot pathogen Pseudocercosporella herpotrichoides

Mycelial isolates (115) of Pseudocercosporella herpotrichoides were obtained from five field sites in England. Carbendazim-resistant isolates were detected by their mycelial growth on agar containing 1 μg/ml carbendazim. Resistant isolates were found at two of the five sites examined and one of these had never been treated with benzimidazole fungicides. Amongst the carbendazim- resistant isolates there was a predominance of isolates with pale mycelium, an irregular colony margin and a relatively slow growth rate; however, this association was not absolute. Large differences in the effects of carbendazim on mycelial growth of sensitive and resistant isolates were demonstrated; growth of sensitive isolates was completely inhibited at 0.5 μg /ml carbendazim whilst five of the six resistant isolates examined grew on agar containing 1000 μg/ml fungicide. The carbendazim-resistant isolates were cross-resistant to benomyl, thiophanate-methyl and to a Icsser degree thiabendazole, but not to prochloraz. Conidia of carbendazim-resistant isolates were as resistant. Carbendazim-resistant isolates were just as pathogenic to wheat as sensitive isolates. The implications of these results and other reports of benzimidazole resistance in P. herpotrichoides are discussed in relation to disease control.     

Sensitivity of South African Ramulispora herpotrichoides isolates to carbendazim and ergosterol biosynthesis inhibitors

In a survey conducted during 1991–1992, single-spored isolates of the eyespot fungus from the Swartland area were characterized and tested for sensitivity to carbendazim and ergosterol inhibiting fungicides. The 100 isolates tested were all fast growing, even marginate, and designated as Ramulispora herpotrichoides . Fungal growth was completely inhibit on PDA amended with carbendazim (1 μg/ml), indicating that the local population of the fungus is still at baseline sensitivity to benzimidazoles. The mean concentration of prochloraz calculated to inhibited growth by 50% (IC₅₀ value) was 0.043 ± 0.029 μg/ml, which is comparable with the baseline sensitivity reported for European isolates. Of the 36 representative isolates screened against 2 μg/ml triadimenol, 44% were sensitive, while 36% were resistant. The triadimenol-resistant isolates were sensitive to propiconazole and flusilazole. However, four of the triadimenol-resistant isolates were also resistant to tebuconazole. These results indicate that South African isolates of R. herpotrichoides are sensitive towards carbendazim, prochloraz, propiconazole and flusilazole. They were found to differ, however, in sensitivity towards triadimenol and tebuconazole, where some isolates had an IC₅₀ value greater than 2 μg/ml.