柑橘炭疽病的病原鉴定和综合防治措施

采集桔园感病柑橘,进行病原菌分离鉴定并研究了其对农药的敏感性、形态学和ITS1-5.8S rDNA-ITS2序列分析。结果表明:病原菌为胶孢炭疽菌（Colletotrichum gloeosporioides）;对11种市售农药都具有敏感性,其中氟硅唑、中生菌素、多抗霉素、丙森锌、氟菌唑、异菌脲6种药物对病菌菌丝生长的抑制活性较高,以氟硅唑最为灵敏,其EC₅₀为0.041μg/mL,丙森锌和中生菌素次之,EC₅₀分别为1.59、4.73μg/mL;氟硅唑和百菌清对孢子的抑制效果较好,丙森锌、佳爽和多抗霉素也有一定的保护作用。根据药敏试验和文献方法制定了综合防治方案。     

杀菌剂在莲瓣兰原生地萌发胚培养中的应用

以莲瓣兰杂交种子原生地播种萌发突破种皮后的胚为外植体,研究了培养基中添加不同种类、不同浓度的杀菌剂对胚培养过程中真菌污染的控制作用。结果表明:培养基中添加培福朗、苯菌灵和代森锰锌能有效控制莲瓣兰杂交种子原生地萌发突破种皮后的胚培养过程中的真菌污染,胚污染率可以控制在10.0%以内,培养基中添加培福朗时胚成活率显著高于添加苯菌灵和代森锰锌,胚成活率高达92.4%;培养基中培福朗浓度在0.5～1.0mg/L范围内时胚污染率能够控制在9.0%以内,胚成活率超过92.3%,不仅能有效控制莲瓣兰杂交种子原生地萌发突破种皮后的胚培养过程中真菌污染,还能促进胚生长发育转绿成根状茎。     

Guanidinium and amidinium fungicides: A new class of carbocation mimetic ergosterol biosynthesis inhibitors

A novel class of chemical has been designed with the aim of inhibiting the Δ¹⁴-reductase and Δ⁸-Δ⁷-isomerase enzymes in the ergosterol biosynthesis pathway in fungi. Use was made of knowledge about the mechanisms of both enzymes and the mode of action of known, fungicidal inhibitors of these enzymes. Pioneer examples have been synthesised and have been demonstrated to be potent inhibitors of ergosterol biosynthesis in Ustilago maydis (DC) Corda, acting in the same manner as the commercial fungicide fenpropimorph. They also showed excellent fungicidal activity against Erysiphe graminis DC f. sp. hordei Marchal (powdery mildew of barley) and Puccinia recondita Rob. ex Desm. (wheat leaf rust) in in-vivo glasshouse tests. Using these compounds as a starting point, systematic structural variation has been carried out. Testing of a wide range of analogues at high volume confirms the potential of this class of compound to control mildew and rust pathogens at levels comparable to those of the standards. Correlation of in-vivo and enzymatic data is good and the structure-activity relationship developed for this series of compounds closely parallels that found for the morpholine/piperidine class of fungicides, suggesting a common mode of action.     

Differential Control of Head Blight Pathogens of Wheat by Fungicides and Consequences for Mycotoxin Contamination of Grain

Fusarium head blight of wheat is caused by a disease complex comprised of toxigenic pathogens, predominantly Fusarium spp., and a non-toxigenic pathogen Microdochium nivale, which causes symptoms visually indistinguishable from Fusarium and is often included as a causal agent of Fusarium head blight. Four field trials are reported here, including both naturally and artificially inoculated trials in which the effect of fungicide treatments were noted on colonisation by Fusarium and Microdochium, and on the production of deoxynivalenol (DON) mycotoxin. The pathogen populations were analysed with quantitative PCR and samples were tested for the presence of the mycotoxin DON. Application of fungicides to reduce Fusarium head blight gave a differential control of these fungi. Tebuconazole selectively controlled F. culmorum and F. avenaceum and reduced levels of DON, but showed little control of M. nivale. Application of azoxystrobin, however, selectively controlled M. nivale and allowed greater colonisation by toxigenic Fusarium species. This treatment also lead to increased levels of DON detected. nobreak Azoxystrobin application two days post-inoculation increased the production of DON mycotoxin per unit of pathogen in an artificially inoculated field trial. This result indicates the potential risk of increased DON contamination of grain following treatment with azoxystrobin to control head blight in susceptible wheat cultivars. This is the first study to show differential fungicidal control of mixed natural pathogen populations and artificial inoculations in field trials.     

Metalaxyl sensitivity of isolates of Phytophthora erythroseptica in Prince Edward Island

Isolates of Phytophthora erythroseptica , causal agent of pink rot of potato, were obtained from diseased tubers collected in Prince Edward Island (PEI), Canada. In an in vitro assay of field and single-zoospore isolates, all isolates of the pathogen from PEI were sensitive to metalaxyl (EC₅₀ < 0·5  µ g mL⁻¹), unlike moderately or highly resistant reference isolates obtained from Maine, USA. Allozyme-banding patterns at the glucose-6-phosphate isomerase ( Gpi ) locus were identical (91/91) for all isolates of P. erythroseptica examined from PEI and Maine, but could be used to distinguish isolates of P. erythroseptica from local isolates of Phytophthora infestans . Inoculation of potato tubers from plants treated with foliar applications of metalaxyl in the field indicated that compounds inhibitory to metalaxyl-sensitive isolates of P. erythroseptica were present in the periderm, even after 4 months' storage. By contrast, moderately or highly resistant isolates of the pathogen caused significantly ( P  ≤ 0·05) more disease than sensitive isolates in tubers from plants treated with metalaxyl. The effectiveness of metalaxyl in controlling pink rot in a particular region will depend on resistance levels of local populations of P. erythroseptica . Preventing the development and spread of resistant strains of P. erythroseptica will be critical in maintaining metalaxyl as an effective chemical for control of this pathogen.     

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.     

苜蓿干草捆安全贮藏条件的研究

通过对苜蓿打捆密度(50、100、150、200 kg·m^-3)、打捆含水量(14%~16%、19%~21%、24%~26%、29%~31%)和防霉剂添加量(0%、1%、2%、3%)3个因素开展研究,筛选苜蓿草捆最佳的贮藏方式,为我国优质苜蓿干草生产提供理论基础。对苜蓿打捆的3个因素设计正交试验,不同处理苜蓿草捆在贮藏360 d后,对其营养物质、饲用价值和体外消化特性3个方面综合研究,确定出苜蓿草捆的最适贮藏条件。试验一:通过不同试验处理对苜蓿干草营养影响试验,从营养成分和饲用价值综合考虑,处理A₁₀(打捆密度100 kg·m^-3,打捆含水量24%~26%,CaO添加量3%)、A₁₂(打捆密度200 kg·m^-3,打捆含水量24%~26%,CaO添加量1%)、A₁₄(打捆密度100 kg·m^-3,打捆含水量29%~31%,CaO添加量2%)和A₁₅(打捆密度150 kg·m^-3,打捆含水量29%~31%,CaO添加量1%)在贮藏360 d的苜蓿草捆各项营养指标损失相对较少,其饲用价值也相对较高。试验二:通过试验一筛选出的4个较优处理,以A₁(打捆密度50 kg·m^-3,打捆含水量14%~16%,CaO添加量0)和A₁₆(打捆密度200 kg·m^-3,打捆含水量29%~31%,CaO添加量0)为对照。通过不同试验处理苜蓿干草体外消化试验,在体外培养48 h过程中,处理A₁₄的产气量最高为53.13 mL,显著高于对照(P<0.05);A₁₄的体外培养液在各个时间点的pH都低于其他处理,其pH平均值最低为6.64;A₁₄的总挥发性脂肪酸(TVFA)含量最高为61.05 mol·L^-1,极显著高于其他各个处理(P<0.01);A₁₄的粗蛋白(CP)和干物质(DM)的降解率最高,分别为81.21%和66.84%,极显著高于其他处理(P<0.01)。从营养物质、饲用价值和体外消化特性综合考虑,苜蓿干草在高水分(29%~31%)、中密度(100 kg·m^-3)打捆,并添加2%的氧化钙防霉剂,在贮藏过程中营养保存最完好,饲用价值最高,体外消化特性最好。     

防治玉米叶斑病高效药剂筛选及药剂减施增效技术

为有效防治玉米小斑病和弯孢叶斑病并减少化学农药使用量,本研究采用菌丝生长速率法从11种杀菌剂中选取抑菌效果较好的8种药剂进行田间小区药效试验。同时选取对两种叶部病害兼具防效的最佳药剂再与中量元素水溶肥、腐植酸、氨基寡糖素、芸苔素内酯等产品混配开展田间药效试验,确定该药剂田间施用浓度和增效组合。结果显示,各供试药剂对2种病菌菌丝生长具有不同的抑制作用,其中25%丙环唑EC、25%戊唑醇WP、40%氟硅唑EC、30%氟菌唑WP、12.5%烯唑醇WP在供试各浓度下对2种病菌抑制率均为100%,田间小区药效筛选测定中,25%戊唑醇WP防治效果最好,对玉米小斑病和弯孢叶斑病两种叶部病害防效分别为81.07%和72.22%。田间试验中,25%戊唑醇WP防治玉米小斑病和弯孢叶斑病的最佳施用浓度为2 000倍液,防效分别为59.48%和53.96%。在减量50%情况下防效有所下降,配施氨基寡糖素后,防效可提高37.40百分点和22.98百分点,与最佳施用浓度防效相当,达到了减药增效的作用。     

小麦不同抗性品种对6种杀菌剂防治小麦白粉病效果的影响

在河北廊坊采用田间小区试验对种植不同抗性小麦品种情况下6种杀菌剂防治白粉病的效果进行了研究。结果表明, 6种杀菌剂中18%烯肟菌酯·氟环唑SC和20%烯肟菌酯·戊唑醇SC在抗病品种和感病品种上的田间小麦白粉病防效均显著优于20%三唑酮EC, 所有供试杀菌剂同一使用剂量下在高抗品种‘保丰104’上的防效要显著高于感病品种‘京双16’上的防效, 甚至较低剂量施药水平下(105 g/hm2)在‘保丰104’上对白粉病的防效要高于或显著高于高剂量施药水平下(150 g/hm2)在‘京双16’上的防效, 但参试的多数杀菌剂同一施药量情况下在中感品种‘众麦2号’和高感品种‘京双16’上的防效无显著差异。该研究说明以抗性品种为基础, 结合使用合适的杀菌剂, 可有效减少杀菌剂施用量, 此研究结果可为杀菌剂的减量施用提供依据。     

核果类果树褐腐病在重庆的发生与防治初报

近年随着乡村产业调整和果业发展, 褐腐病在我国的发生呈加重趋势。本文对重庆地区核果类果树褐腐病的发生状况做了调查分析, 在室内通过平板及离体果实试验, 筛选拮抗菌和化学药剂, 为田间防治实践提供科学依据。主要结果如下:桃褐腐病在重庆普遍发生, 核果类果树均易感, 病原菌经鉴定为果生链核盘菌Monilinia fructicola; 系统调查初步分析发现, 降雨时间与李褐腐病发生发展关系最密切, 其与病情指数增幅的相关系数R=0.94(P<0.05); 平板对峙和离体桃果筛选, 获得2株有生防潜力的放线菌YLS5-2和YYDB3-1, 二者的抑菌率分别为91.3%和84.5%, 相对防效分别为65.1%和67.1%, 可能具有较好的应用前景; 平板毒力测定和离体桃果控病试验, 效果最优的化学药剂分别为戊唑醇、苯甲·丙环唑, 其中戊唑醇在推荐浓度处理96 h其离体果实防效仍维持在100%水平。