不同杀菌剂对小麦赤霉病及籽粒DON毒素的控制效果

为探明不同杀菌剂对小麦赤霉病和小麦籽粒DON毒素(包括DON、3-ADON和15-ADON)的控制效果, 采用菌丝生长速率法测定了12种药剂对禾谷镰刀菌野生型菌株PH-1的室内活性, 同时采用液相色谱-串联质谱法(LC-MS)测定了这些药剂对DON毒素的抑制效果, 并开展了小麦赤霉病及籽粒DON毒素的田间防治试验。结果表明, 12种原药对菌丝生长抑制活性强弱依次为氟唑菌酰羟胺>咪鲜胺>戊唑醇>丙硫菌唑>叶菌唑>氰烯菌酯>氟环唑>多菌灵>甲基硫菌灵>吡唑醚菌酯>嘧菌酯>井冈霉素A。氟环唑EC50和EC90离体胁迫均刺激DON毒素产生, 其他杀菌剂EC50和EC90胁迫均抑制DON毒素产生。田间试验结果表明, 200 g/L氟唑菌酰羟胺SC、30%丙硫菌唑OD和20%叶菌唑WP病指防效和DON防效为87.68%~94.77%; 430 g/L戊唑醇SC、25%氰烯菌酯SC、45%咪鲜胺EW、25%氟环唑SC、50%多菌灵WP和70%甲基硫菌灵WP病指防效和DON防效为57.63%%~85.49%; 250 g/L吡唑醚菌酯EC和250 g/L嘧菌酯SC病指防效分别为72.18%和51.98%, DON防效分别为43.06%和-7.96%; 24%井冈霉素A AS病指防效和DON防效分别为42.37%和62.87%。药剂离体和田间控毒效果不完全一致, 赤霉病有效防控是DON防控的前提, 病害防效与DON防效不完全一致, 本研究为小麦赤霉病及籽粒DON毒素防控提供了科学依据。     

Relationship Between Growth and Mycotoxin Production by Fusarium species, Biocides and Environment

Fusarium head blight of cereals has, in recent years, become one of the most important pre-harvest diseases worldwide. This paper examines the in vitro efficacy of fungicides to control Fusarium species in cereals and the efficacy in the field on both Fusarium infection of ripening ears as well as their impact on mycotoxin production. Field studies suggest that fungicides such as tebuconazole and metconazole give good control of both Fusarium infection of ears and control of deoxynivalenol (DON) production. However, azoxystrobin and related fungicides are less effective, and grain from treated crops has sometimes been found to have increased concentrations of DON and nivalenol. Studies of isolates of Fusarium culmorum from different parts of Europe showed that complex interactions occur between environmental factors, fungicide type and isolate in relation to growth inhibition and DON production. These studies confirmed the ineffectiveness of azoxystrobin and suggest that environmental stress factors, particularly water availability and temperature, and low fungicide doses may stimulate mycotoxin production by Fusaria in vitro and in wheat grain.     

Monogenic resistance to a new fungicide, JS399-19, in Gibberella zeae

The fungicide JS399-19 is a novel cyanoacrylate fungicide active against Gibberella zeae , and has been marketed in China for control of fusarium head blight (FHB) on wheat. Forty-three isolates sensitive to fungicide JS399-19 were collected from three commercial wheat fields in China. Forty-five isolates resistant to JS399-19, obtained from five sensitive isolates by selection for resistance to JS399-19, were selected. Three sensitivity levels were identified: sensitive (S), moderately resistant (MR) and highly resistant (HR) to JS399-19, based on a previous study. Eight isolates representing the three sensitivity-level phenotypes were randomly selected for a study on the inheritance of JS399-19 resistance by analysing the sensitivity of hybrid F₁ progeny. A nitrate-non-utilizing mutant ( nit ) was used as a genetic marker to confirm that individual perithecia were the result of outcrossing. Five crosses were assessed: S × S, S × HR, MR × HR, HR × HR and MR × S. In crosses between parents with different sensitivity levels, such as S × HR, MR × HR and MR × S, the progeny fitted a 1:1 segregation ratio of the two parental phenotypes. No segregation was observed in the crosses S × S and HR × HR. It was concluded that the MR and HR phenotypes in G. zeae were conferred by different allelic mutations within the same locus. In these isolates, resistance to JS399-19 was not affected by modifying genes or cytoplasmic components.     

Meta-analysis of yield response of hybrid field corn to foliar fungicides in the U.S. Corn Belt

The use of foliar fungicides on field corn has increased greatly over the past 5 years in the United States in an attempt to increase yields, despite limited evidence that use of the fungicides is consistently profitable. To assess the value of using fungicides in grain corn production, random-effects meta-analyses were performed on results from foliar fungicide experiments conducted during 2002 to 2009 in 14 states across the United States to determine the mean yield response to the fungicides azoxystrobin, pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin. For all fungicides, the yield difference between treated and nontreated plots was highly variable among studies. All four fungicides resulted in a significant mean yield increase relative to the nontreated plots (P < 0.05). Mean yield difference was highest for propiconazole + trifloxystrobin (390 kg/ha), followed by propiconazole + azoxystrobin (331 kg/ha) and pyraclostrobin (256 kg/ha), and lowest for azoxystrobin (230 kg/ha). Baseline yield (mean yield in the nontreated plots) had a significant effect on yield for propiconazole + azoxystrobin (P < 0.05), whereas baseline foliar disease severity (mean severity in the nontreated plots) significantly affected the yield response to pyraclostrobin, propiconazole + trifloxystrobin, and propiconazole + azoxystrobin but not to azoxystrobin. Mean yield difference was generally higher in the lowest yield and higher disease severity categories than in the highest yield and lower disease categories. The probability of failing to recover the fungicide application cost (p(loss)) also was estimated for a range of grain corn prices and application costs. At the 10-year average corn grain price of $0.12/kg ($2.97/bushel) and application costs of $40 to 95/ha, p(loss) for disease severity <5% was 0.55 to 0.98 for pyraclostrobin, 0.62 to 0.93 for propiconazole + trifloxystrobin, 0.58 to 0.89 for propiconazole + azoxystrobin, and 0.91 to 0.99 for azoxystrobin. When disease severity was >5%, the corresponding probabilities were 0.36 to 95, 0.25 to 0.69, 0.25 to 0.64, and 0.37 to 0.98 for the four fungicides. In conclusion, the high p(loss) values found in most scenarios suggest that the use of these foliar fungicides is unlikely to be profitable when foliar disease severity is low and yield expectation is high.     

Management of wheat blast with synthetic fungicides,partial resistance and silicate and phosphite minerals

Field trials conducted on a yellow-red latossol (pH 6.0), replicated in 2010 and 2011, sought to examine the effect of silicon, phosphite minerals, synthetic fungicides and genetic resistance for wheat blast management (Magnaporthe grisea) in Central Brazil. Disease intensity was measured on cvs. BRS 264 and BR18 subjected to the following Si treatments: pre-plant furrow application of Ca & Mg silicate (300 kg ha^-1); post-plant scattered application of Ca & Mg silicate on top of the soil (1 ton ha^-1); multiple foliar SiO₂ applications (30 g l ^-1); and non-treated control. Blast incidence and severity were scored. Further experiments were conducted on cv. BR-264, for examination of the effect of potassium phosphite and synthetic fungicides on wheat blast intensity, with the following treatments: K₂HPO₃ (1ml l ^-1); epoxinazole + pyraclostrobin (700 ml ha^-1); tebuconazole (600 ml ha^-1); tebuconazole + trifloxystrobin (750 ml ha^-1); and non-treated control. In 2010, disease intensity was lower than in 2011. In the silicate experiments, disease was significantly lower when plants were treated with foliar or furrow silicate. Si applications significantly reduced disease in BRS-264. While BR-18 consistently demonstrated lower disease levels, cv. BRS-264 generally responded more markedly to silicon applications. In the phosphite/fungicide experiment of 2010, all treatments reduced disease when compared with the control, and in 2011 phosphite efficiency was not significantly different from some fungicide treatments. Synthetic fungicides demonstrated an average blast control of 55% by severity values. Yields were increased in the phosphite-treated plots (by 9–80%), in the Si treatments (by 26–92%), and more so, and more consistently, with synthetic fungicides (by 90–121%). Combined results of all field studies, carried out under environmental conditions highly conducive to disease, indicated that control of wheat blast necessitates the joint integration of several alternatives for efficient disease management.     

4种杀菌剂对紫皮石斛锈病的田间药效评价

针对紫皮石斛锈病。试验选用10%苯醚甲环唑WG,250 g/L嘧菌酯SC,29%吡萘·嘧菌酯SC,75%肟菌·戊唑醇WG 4种杀菌剂进行田间药效试验。结果表明:复配剂29%吡萘·嘧菌酯SC 600 mL/hm~2与75%肟菌·戊唑醇WG 300 g/hm~2,防效相当且显著高于其余两个施药处理,在第3次施药后7 d时达最高防效分别为87.70%和88.56%,鲜重折合产量比空白对照分别增产13.48%、13.22%,可在实际生产中交替使用。     

Sensitivity of populations ofBotrytis cinerea to triazoles,benomyl and vinclozolin

Sensitivity of field isolates (121) ofBotrytis cinerea from France (1992), Germany (1979–1992), Israel (1990) and the Netherlands (1970–1989) to the triazoles tebuconazole and triadimenol, the benzimidazole benomyl and the dicarboximide vinclozolin were tested in radial growth experiments. Resistance to benomyl (in 21 to 100% of isolates tested) and vinclozolin (in 25 to 71% of isolates tested) was common in most countries. EC₅₀s (concentrations of fungicides inhibiting radial mycelial growth ofB. cinerea on B5-agar by 50%) for tebuconazole and triadimenol ranged between 0.01–1.64 and 0.4–32.6g ml^–1, respectively, and were log-normally distributed. The variation factor (ratio between EC₅₀s of the least and most sensitive isolate tested) amounts 164 and 82 for tebuconazole and triadimenol, respectively. These values are comparable to those for azole fungicides applied in control of other pathogens. Hence, variation in sensitivity to triazoles can probably not explain limited field performance of triazoles towardsB. cinerea. Isolates from south west Germany (1992) were significantly less sensitive to tebuconazole than isolates collected earlier in Germany, Israel and the Netherlands. Such less sensitive populations may contribute to the limited field performance of DMI fungicides towardsB. cinerea. The sensitivity of isolates from south west Germany to tebuconazole was similar to that of DMI-resistant mutants generated in the laboratory. These mutants displayed stable resistance with Q-values (ratio between EC₅₀ of resistant mutant and wild type isolate) between 5 and 20. Sensitivity of field isolates and laboratory mutants to tebuconazole and triadimenol was correlated.     

防治白背飞虱的农药复配增效配方筛选

农药复配制剂的研究对于延长新农药品种的使用寿命、缓解靶标生物的抗性、扩大防治谱、降低防治成本、提高药效和环境安全性等具有重要的意义。为筛选防治白背飞虱的农药增效复配配方,采用稻茎浸渍法测定了8种农药单剂及复配剂对白背飞虱3龄若虫的毒力。利用共毒因子法定性筛选出16组共毒因子大于20的配比,并对其中15组进一步利用共毒系数法定量筛选,得到有增效作用的5组配比,分别为烯啶虫胺与毒死蜱按1∶30配比以及吡虫啉与异丙威分别按7∶40、7∶200、7∶400和7∶1 000配比;其共毒系数分别为112.5、242.1、212.4、638.1、417.7,其中吡虫啉与异丙威按7∶400配比具有最显著增效作用。     

氰烯菌酯对禾谷镰孢菌的生物活性及其内吸输导性研究

氰烯菌酯(2-氰基-3-氨基-3-苯基丙烯酸乙酯,JS399-19) 是一种对禾谷镰孢菌具有专化活性的新型杀菌剂。研究表明,该药在离体条件下对禾谷镰孢菌Fusarium graminearum抗多菌灵菌株及野生敏感菌株的菌丝生长均有很高的抑制活性,平均EC50值分别为0.117±0.036和0.107±0.020 μg/mL 。氰烯菌酯不能抑制禾谷镰孢菌的分生孢子萌发,但能引起抗多菌灵菌株及敏感菌株的分生孢子萌发后的芽管畸形。活体条件下,氰烯菌酯灌根处理对小麦赤霉病有一定防效,在叶片间的输导性较差,不能被小麦穗颈吸收;该药在同一张叶片上仅表现为向上输导,对处理部位的下部几乎没有防效。用400 μg/mL氰烯菌酯和400 μg/mL多菌灵穗部喷雾处理前1 、2 、3 d接种禾谷镰孢菌分生孢子,氰烯菌酯对小麦赤霉病的防效分别为95%、75%和62%;处理后1 、2 、3 d 接种,防效分别为88%、78%和73%,而对照药剂多菌灵的防效较差。说明氰烯菌酯对小麦赤霉病有优异的保护和治疗作用,在禾谷镰孢菌对多菌灵已产生抗性的地区,氰烯菌酯可以作为一种很好的替代药剂用于防治小麦赤霉病。     

Sensitivity ofFusarium graminearum to fungicide JS399-19:In vitro determination of baseline sensitivity and the risk of developing fungicide resistance

The baseline sensitivity ofFusarium graminearum Schwade [teleomorph =Gibberella zeae (Schweinitz) Petch] to the fungicide JS399-19 (development code no.) [2-cyano-3-amino-3-phenylacrylic acetate] and the assessment of risk to JS399-19 resistancein vitro are presented. The mean EC₅₀ values for JS399-19 inhibiting mycelial growth of three populations of wild-typeF. graminearum isolates were 0.102±0.048, 0.113±0.035 and 0.110±0.036 μg ml⁻¹, respectively. Through UV irradiation and selection for resistance to the fungicide, we obtained a total of 76 resistant mutants derived from five wild-type isolates ofF. graminearum with an average frequency of 1.71 × 10⁻⁷% and 3.5%, respectively. These mutants could be divided into three categories of resistant phenotypes with low (LR), moderate (MR) and high (HR) level of resistance, determined by the EC₅₀ values of 1.5–15.0 μg ml⁻¹, 15.1–75.0 μg ml⁻¹ and more than 75.0 μg ml⁻¹, respectively. There was no positive cross-resistance between JS399-19 and fungicides belonging to other chemical classes, such as benzimidazoles, ergosterol biosynthesis inhibitors and strobilurins, suggesting that JS399-19 presumably has a new biochemical mode of action. Although the resistant mutants appeared to have comparable pathogenicity to their wild-type parental isolates, they showed decreased mycelial growth on potato-sucrose-agar plates and decreased sporulation capacity in mung bean broth. Nevertheless, most of the resistant mutants possessed fitness levels comparable to their parents and had MR or HR levels of resistance. As these studies yielded a high frequency of laboratory resistance inF. graminearum, appropriate precautions against resistance development in natural populations should be taken into account. http://www.phytoparasitica.org posting August 7, 2008.     

不同杀菌剂对玉米白斑病的田间防治效果

玉米白斑病是我国西南玉米产区一种新发病害, 尚缺乏有效的防控措施。为筛选玉米白斑病的防控药剂, 本研究选用19种不同作用机制的杀菌剂, 于2022年－2023年在云南省普洱市开展田间试验, 分别于玉米10叶期和抽雄吐丝期采用叶面喷雾法施药1次, 评价各药剂的田间防效。结果显示, 9种防治真菌性病害的杀菌剂在最后1次施药后28 d对白斑病的防治效果超过50%, 包括250 g/L嘧菌酯悬浮剂、40%氟环唑悬浮剂、24%井冈霉素A水剂、40%咪鲜胺水乳剂和10%苯醚甲环唑微乳剂5种单剂, 以及325 g/L苯甲·嘧菌酯悬浮剂、40%丁香·戊唑醇悬浮剂、40%唑醚·戊唑醇悬浮剂和30%氟环·咪鲜胺微乳剂4种混剂。保护性杀菌剂代森锰锌和有机铜杀菌剂喹啉铜仅表现了23.26%和29.00%的微弱防效。卵菌病害特效药剂烯酰吗啉, 防治细菌性病害的杀菌剂春雷霉素、四霉素、中生菌素以及植物免疫诱抗剂6%寡糖·链蛋白可湿性粉剂的防效较差, 均低于20%。本研究发现部分甲氧基丙烯酸酯类和三唑类杀菌剂对玉米白斑病具有较好的田间防治效果, 建议现阶段在生产上采用二者的复配药剂如苯甲·嘧菌酯, 唑醚·戊唑醇等开展田间防控。     

禾谷镰孢菌对氰烯菌酯的敏感性基线及室内抗药性风险初步评估

 本文报道了禾谷镰孢菌(Fusarium graminearum)对氰烯菌酯(2-氰基-3-氨基-3-苯基丙烯酸乙酯,JS399-19)的敏感性基线及其抗药性风险。离体条件下氰烯菌酯对51个禾谷镰孢菌菌株的平均EC₅₀和MIC值分别为(0.153±0.050)μg/mL和小于4.0μg/mL;通过紫外线照射和药剂驯化的方法获得了14个禾谷镰孢菌对氰烯菌酯的抗药性突变体,紫外光诱变抗药性突变频率为1.67×10^-7。这些突变体的抗性水平可分为低、中、高3种类型,其EC₅₀分别为1.5~15.0μg/mL、15.1~75.0μg/mL和75.0μg/mL以上。与亲本菌株2021相比,抗药突变体间的菌丝生长量和产生子囊壳能力发生不同程度的增加或下降,而分生孢子繁殖量则显著下降。在无药培养基上菌丝体转代培养8次后,抗药水平保持不变,且与亲本菌株有相同的致病性。所测定的突变体在含1%葡萄糖的PDA上菌丝生长除UV-2021-4显著下降外,其余都表现生长速率比亲本显著增加。在含3%和4%葡萄糖的PDA上2021生长优于亲本菌株。氰烯菌酯与苯并咪唑类、麦角甾醇生物合成抑制剂类、甲氧基丙烯酸酯类、二硫代氨基甲酸盐类和取代芳烃类杀菌剂没有交互抗性。     

Effect of Dose Rate of Azoxystrobin and Metconazole on the Development of Fusarium Head Blight and the Accumulation of Deoxynivalenol (DON) in Wheat Grain

Glasshouse studies were undertaken to determine if fungicides used for the control of Fusarium head blight (FHB) result in elevated concentrations of the trichothecene mycotoxin, deoxynivalenol (DON) in harvested wheat grain. Metconazole and azoxystrobin, at double, full, half or quarter the manufacturer's recommended dose rate, were applied to ears of wheat (cv. Cadenza), artificially inoculated with conidia of either Fusarium culmorum or F. graminearum. Metconazole demonstrated high activity against both pathogens, reducing significantly the severity of FHB and the DON concentrations at each of the four dose rates tested when compared to untreated controls. Applications of azoxystrobin significantly reduced FHB and DON compared to unsprayed controls. However, their effectiveness was significantly less than that of metconazole and no dose rate response was observed. Quantification of the amount of trichothecene-producing Fusarium present in harvested grain was determined using a competitive PCR assay based on primers derived from the trichodiene synthase gene (Tri5). Simple linear regression analyses revealed strong relationships between the amount of trichothecene-producing Fusarium present in grain and the DON concentrations (r ²=0.72–0.97). It is concluded that fungicides, applied for the control of FHB, affect DON concentrations indirectly by influencing the amount of trichothecene-producing Fusarium species present in wheat grain. There was no evidence that fungicide applications directly increase the concentration of DON in grain.     

Proteomic analysis of Fusarium graminearum treated by the fungicide JS399-19

JS399-19 (2-cyano-3-amino-3-phenylancryic acetate), a novel cyanoacrylate fungicide, has powerful inhibition against Fusarium species, especially to Fusarium graminearum. Treated with JS399-19, mycelium of F. graminearum was distorted and swelled. The embranchment increased. In order to investigate the effect of JS399-19 on protein expression of F. graminearum, total protein of F. graminearum cultured in normal condition and that treated with 0.5 μg/mL (EC₉₀ value) JS399-19 were extracted respectively and proteomic analysis was performed using two-dimensional gel electrophoresis. The expression levels of 38 proteins varied quantitatively at least twofold. 33 proteins out of the 38 were successfully identified by MALDI-TOF-MS/MS and MASCOT. According to the classification of physiological functions from Conserved Domain Database analysis, 19, 5, 2, 3, 2 and 2 proteins were respectively associated with metabolism, regulation, motility, defense, signal transduction, and unknown function, which indicated that energy metabolism, the synthesis and transport of proteins and DNA of F. graminearum were inhibited by JS399-19 in different degrees. The expression levels of the genes were further confirmed by quantitative real-time PCR analyses. This study represents the first proteomic analysis of F. graminearum treated by JS399-19 and will provide some useful information to find the mode of action of the fungicide against F. graminearum.     

嘧菌酯对河南省小麦茎基腐病菌的抑制活性及对病害的防治效果

主要由假禾谷镰孢Fusarium pseudograminearum引起的茎基腐病是小麦上的重要病害,对产量及质量都有严重影响,目前尚无登记应用在该病害防治上的化学药剂。本研究从河南省17个地市采集病害样本,分离纯化得到82株小麦茎基腐病菌菌株,包括76株假禾谷镰孢和6株禾谷镰孢。嘧菌酯抑制76株假禾谷镰孢孢子萌发的EC₅₀值为0.02～1.54μg/mL,平均EC₅₀值为(0.33±0.29)μg/mL;经数据异常值检验,舍弃异常菌株LHWY-6及SQYC-6后,嘧菌酯对74株(97.37%)正常菌株的平均EC₅₀值(0.30±0.24)μg/mL可作为假禾谷镰孢对嘧菌酯的敏感性基线;不同地市菌株间敏感性存在差异,同一地市菌株间对嘧菌酯的敏感性差异较大,许昌、焦作、洛阳和商丘4市的菌株间敏感性差异倍数均在20.00以上,南阳、三门峡和开封3地的菌株间差异倍数均在2.00以下,其他地市菌株间差异倍数在2.70～12.00之间;假禾谷镰孢孢子萌发对嘧菌酯与其对丙硫菌唑、多菌灵、咯菌腈、氰烯菌酯、吡唑醚菌酯和戊唑醇的敏感性相...     

Fusarium ear blight of wheat: the use of quantitative PCR and visual disease assessment in studies of disease control

Quantitative PCR analysis and visual disease assessment (VDA) were used to study Fusarium culmorum and F. poae ear blight of wheat and its fungicidal control in three glasshouse trials (1994–5 and 1996–7). VDA indicated high levels of both diseases in the trials, while PCR analysis showed that the amounts of F. poae detected in infected plants were low relative to the amounts detected for F. culmorum . PCR and VDA analysis both indicated that the demethylase-inhibiting (DMI) fungicides prochloraz and tebuconazole significantly decreased F. culmorum and F. poae ear blight. The PCR results, however, revealed levels of disease control by fungicide treatments that were consistently higher than those suggested by VDA. Overall, both fungicides appeared equally effective in controlling the two pathogens. PCR and VDA analysis indicated that the anilino-pyrimidine fungicide pyrimethanil had no significant effect on F. culmorum ear blight. Correlations between VDA at cereal growth stage 80 and PCR analysis were similar for F. culmorum and F. poae . Yield analysis, as measured by 1000 grain weight, indicated that DNA content more accurately predicted yield loss than did VDA scores. Inoculation with F. culmorum significantly reduced yield and significant relationships were observed between F. culmorum disease (as assessed visually or by PCR) and yield, with yield decreasing as disease increased. In contrast, inoculation with F. poae had no significant effect on yield and no significant relationships were observed between F. poae disease and yield. These results have important implications for field studies of Fusarium ear blight of wheat because they highlight the importance of identification of the causal organisms to the species level.     

Effect of Fungicide Application Timing on <Emphasis Type="Italic">Sclerotinia Sclerotiorum</Emphasis> Infection Rate and Yield in Winter Oilseed Rape

In experiments on winter oilseed rape during 2013–2016, we examined the influence of timing of fungicides application at BBCH 61–63 and BBCH 65–67 for fungicides containing active ingredients based upon new triazoles, strobilurins and SDH inhibitors (cyproconazole 80?g/l a.i. + azoxystrobin 200?g/l a.i., picoxystrobin 200?g/l a.i. + cyproconazole 80?g/l a.i., boscalid 200?g/l a.i. + dimoxystrobin 200?g/l a.i., protioconazole 125?g/l a.i. + fluopyram 125?g/l a.i., and prochloraz 276?g/l a.i. + tebuconazole 133?g/l a.i.) on effectiveness against Sclerotinia sclerotiorum and yield. For cyproconazole 80?g/l a.i. + azoxystrobin 200?g/l a.i. and boscalid 200?g/l a.i. + dimoxystrobin 200?g/l a.i., two applications with divided and full doses were also performed. Applications at BBCH 65–67 resulted in a statistically insignificant 4% greater effectiveness against Sclerotinia sclerotiorum. All applications increased yields, but no significant difference was determined due to application timing by growth stages. Divided applications achieved the highest effectiveness, while yield was increased especially at full dosage. In practice, however, such split applications are difficult to perform.     

Chemical control of maize late wilt in the field

Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characterized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. In Israel, the disease has become a major problem in recent years. The pathogen is currently controlled using cultivars of maize having reduced sensitivity. In an earlier work, we modified a molecular method for use as a diagnostic tool to evaluate disease progression in field-infested plants and showed that several fungicides suppressed H. maydis in vitro. Here, we examine the effect of different fungicides on disease progression in a contaminated maize field in the spring and summer of 2009 and 2010. The field was watered using a drip irrigation line for each row and the fungicides were injected directly into the drip line. One of the four fungicides tested, azoxystrobin, was highly effective compared with the control, inhibited the development of wilt symptoms and recovered cob yield by 100%. Although this is the first success in preventing disease symptoms in infested fields in Israel, the azoxystrobin treatment did not reduce the amounts of pathogen DNA in host tissues or delay its spread. Attempts to reduce concentrations of this fungicide or to apply it by spraying were less effective than the triple full dosage treatment. The presence of the pathogen in the host tissues of the successfully treated plants and its ability to undergo pathogenic variations are increasing the risk of pathogen resistance and the urgent need to develop new ways of controlling late wilt.     

番茄叶霉病菌异菌脲抗药性突变体的诱导与生物学性状

测定了苯并咪唑类杀菌剂敏感-乙霉威抗性(BenS-DieR)、苯并咪唑类杀菌剂抗性-乙霉威敏感(BenR-DieS)和苯并咪唑类杀菌剂抗性-乙霉威抗性(BenR-DieR)3种类型的番茄叶霉病菌Cladosporium fulvum菌株对不同类型药剂的敏感性。结果表明,蕃茄叶霉病菌对供试药剂的敏感性与其对苯并咪唑类杀菌剂及乙霉威的敏感性无关。根据药剂对3类菌株EC50值的平均值, 16种杀菌剂抑制菌丝生长的活性依次为腐霉利＞乙烯菌核利＞异菌脲＞戊唑醇＞百菌清＞嘧霉胺＞醚菌酯＞代森锰锌＞8-羟基喹啉铜＞丙环唑＞苯醚甲环唑＞嘧菌酯＞灭锈胺＞烯酰吗啉＞烟酰胺＞三唑酮;抑制孢子萌发的活性依次为醚菌酯＞腐霉利＞百菌清＞乙烯菌核利＞灭锈胺＞8-羟基喹啉铜＞异菌脲＞代森锰锌＞嘧菌酯＞烟酰胺＞嘧霉胺＞戊唑醇＞丙环唑＞苯醚甲环唑＞三唑酮＞烯酰吗啉。通过紫外诱变共获得17株抗异菌脲突变体,突变频率为4.5×10-7。其中低抗、中抗和高抗菌株分别占 17.65%、70.59%和11.75%。这些突变体对腐霉利和乙烯菌核利表现交互抗性,对苯并咪唑类、脱甲基抑制剂(DMIs)、QoIs等药剂的敏感性与亲本菌株之间没有显著性差异,与亲本菌株在生长、产孢、致病能力等方面也无显著差异,但对渗透胁迫的敏感性要显著高于亲本。