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一、发生原因
一是土壤病原菌积累逐年增多.土壤病残体是病菌的主要来源.黄萎病菌以菌丝体、厚垣孢子和拟菌核随病株残体在土壤中越冬,一般可存活6~8年.病菌主要从根部伤口入侵,也可从幼根皮层和根毛入侵,在植株维管束中繁殖.因此,重茬或连作栽培,土壤含菌量多,发病重.二是连年化学肥料的大量投入导致土壤板结,透气性差. 相似文献
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危害棉花苗期的病害主要是棉苗立枯病,且常与棉苗炭疽病、红腐病混发。1、主要症状。棉花播种后至出土前若遭病菌侵害,就会导致烂种、烂芽,不能正常出土。出土后的棉苗在半月内也容易受到病菌的侵害,其症状为棉苗接近土表的根茎部出现黄褐色斑点,后呈长条状褐色凹陷,缢缩成蜂腰状,子叶萎垂,幼苗倒伏枯死。根茎部受害时,韧皮部腐烂呈深褐色纤维状。将病苗自土中拔出时,病部常有菌丝粘带的小土粒。2、传播途径。土壤中的病菌能附着在病残体或没有完全腐熟的堆肥中越冬,将直接侵染棉籽、幼苗。受害棉苗上产生的病菌菌丝可继续危害附近的健苗,扩… 相似文献
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施用生物肥应注意哪些事项 总被引:1,自引:0,他引:1
一、灰霉病
该病可为害叶片、茎、花及果实,病菌主要以菌核在土壤中或以菌丝及分生孢子在病残体上越冬或越夏。花期是侵染高峰期,尤其在果实膨大期浇水过多、湿度高有利发病,病果剧增,是烂果高峰期。 相似文献
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1、立枯病 芦笋立枯病又称枯萎病,是土传病害,初见田内个别植株变黄萎蔫,病情扩展后全珠枯死,嫩茎染病,叶和茎变褐色或纵裂,病株地下茎和根部可现褐色病斑,后期病部腐烂,产生白色至粉红色霉状物,幼笋染病,茎细小或无法出土.病菌为尖孢镰刀菌芦笋专化型,病菌以厚垣孢子在土壤中越冬. 相似文献
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为探讨不同杀菌剂对抑制油菜菌核萌发及子囊盘的杀灭效果,采取室内测定和田间试验的方法,对7种常用杀菌剂的药效以及不同外部条件对菌核萌发、子囊盘数量及其存活率的影响进行试验研究。结果显示,供试7种杀菌剂均能显著抑制菌核萌发,并对子囊盘有显著的杀灭效果,田间防效均达到70%以上;不同外部条件对菌核萌发、子囊盘数量及其存活率有显著影响,在潮湿状态下菌核萌发率达到64.4%,干燥状态下能够存活但不能萌发,水淹状态下菌核死亡率达到90%以上,在药剂处理条件下虽能存活但萌发率较低;杀菌剂处理对不同深度土壤中的菌核萌发的抑制效果存在明显差异,埋土深度大于7cm很少萌发子囊盘,小于4cm能够较好萌发;使用杀菌剂土表喷雾处理能显著抑制菌核萌发产生子囊盘,其抑制率达到66.7%以上,但随埋土深度增加对菌核萌发抑制率明显降低。说明多菌灵、百菌清、菌核净及甲基托布津均可作为今后抑制油菜菌核萌发及杀灭子囊盘的较理想药剂,同时采取稻-油轮作、播栽前土壤深翻或土表药剂处理,能显著降低田间菌源量,是控制病害的有效措施。 相似文献
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Nutting PG 《Science (New York, N.Y.)》1929,70(1817):409-410
Viable sclerotia of the cotton root-rot fungus, Phymatotrichum omnivorum, have been found under natural conditions in the soil of infested cotton fields in Texas, showing that this fungus is a soil organism not restricted to living roots of susceptible host plants, but having an independent means of over-wintering and dissemination. 相似文献
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LI Shi-dong 《中国农业科学(英文版)》2004,3(6)
A field under rice-wheat rotation was selected near Chengdu, China, to study the population of Rhizoctonia solani anastomosis group 1 (AG-l), pathogen causing rice sheath blight disease, in natural soil ecosystem. Inocula of the fungus recovered from the field were divided into three types, i.e., sclerotia, free mycelium retained in the soil passed through a 0.355mm sieve, and colonized plant debris which was subdivided into small colonized debris retained between 2.00 and 0.355mm sieves and large colonized debris retained on 2.00mm sieve after wet screening. Quantitative estimation of the three types of inocula in one year indicated that small colonized debris was the dominant inoculum type for most of the time. The population peaked in March and September at 1 210and 480 colonized debris 100 g-1 air-dry soil respectively, and fell down in December and August to 0 and 177 colonized debris 100 g-1 air-dry soil respectively. Free mycelium was only detectable in March, September and October with 1 209, 7.9 and 14.5 μg fresh wt myceliumg-1 air-dry soil respectively, which corresponded to the two peaks and the second highest level of small debris density in the year. Viable sclerotia and large colonized debris were rare with populations ranging from 0 to 3 for sclerotia and 0 to 14 for large colonized debris 100 g-1 air-dry soil, but were the main structures to survive over winter. It was expected that soil temperature was the main factor determining population dynamics of R.solani AG-1 in natural soil. Optimum temperature for population increasing is predicted to be around 15℃, with a range from 10 to 25℃. Viability tests indicated that 60.9% sclerotia could survive after 265 d being buried in natural sandy loam in field conditions in Beijing, while colonized rice straw debris (0.5 - 1.0 cm long) could not yield the fungus on medium plates after 88d of being buried under the same conditions. 相似文献
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【目的】研究拮抗菌施入棉田土壤后生防菌的数量变化和棉花黄萎病的发病情况,分析生防菌的定殖与防病的相互关系,为生防细菌在棉花黄萎病的防治应用提供理论依据。【方法】选择4株棉花内生和根际拮抗菌Bacillus atrophaeus SHZ-24、Bacillus vanillea SMT-24、Bacillu subtilis SHT-15和Bacillus velezensis BHZ-29进行盆栽试验,使用平板计数和实时荧光定量分析细菌和病原菌。【结果】4株拮抗细菌在土壤中数量变化趋势相同,50 d时的存活量从高到低分别为SHZ-24、BHZ-29、SMT-24、SHT-15,4株拮抗细菌处理均可降低棉苗的病情指数。【结论】BHZ-29的防病效果较好。4株拮抗细菌在土壤中的定殖数量与防病效果呈显著正相关。 相似文献
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《农业科学学报》2017,(7)
With increased cultivation of transgenic Bacillus thuringiensis(Bt) cotton in the saline alkaline soil of China, assessments of transgenic crop biosafety have focused on the effects of soil salinity on rhizosphere microbes and Bt protein residues. In 2013 and 2014, investigations were conducted on the rhizosphere microbial biomass, soil enzyme activities and Bt protein contents of the soil under transgenic Bt cotton(variety GK19) and its parental non-transgenic cotton(Simian 3) cultivated at various salinity levels(1.15, 6.00 and 11.46 dS m~(-1)). Under soil salinity stress, trace amounts of Bt proteins were observed in the Bt cotton GK19 rhizosphere soil, although the protein content increased with cotton growth and increased soil salinity levels. The populations of slight halophilic bacteria, phosphate solubilizing bacteria, ammonifying bacteria, nitrifying bacteria and denitrifying bacteria decreased with increased soil salinity in the Bt and non-Bt cotton rhizosphere soil, and the microbial biomass carbon, microbial respiration and soil catalase, urease and alkaline phosphatase activity also decreased. Correlation analyses showed that the increased Bt protein content in the Bt cotton rhizosphere soil may have been caused by the slower decomposition of soil microorganisms, which suggests that salinity was the main factor influencing the relevant activities of the soil microorganisms and indicates that Bt proteins had no clear adverse effects on the soil microorganisms. The results of this study may provide a theoretical basis for risk assessments of genetically modified cotton in saline alkaline soil. 相似文献
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新疆棉花立枯病根际拮抗细菌的筛选 总被引:5,自引:0,他引:5
为棉花立枯病生物防治提供新的生防细菌菌株,从采集的48份新疆棉苗根际土样中经分离、纯化获得优势细菌菌株189个,采用平板对峙培养法对立枯丝核菌(Rhizoctonia solani)进行根际拮抗细菌的筛选,并对部分抑菌活性强菌株的抑菌作用进行研究。结果表明,共获得根际拮抗细菌菌株67株;其中菌株MX-1抑菌谱广,抑菌活性强,具有几丁质酶活,其盆栽试验防治效果达59.8%;饱和度70%硫酸铵获得的抑菌物质热稳定性较好,抑菌活性最高,能够引起立枯丝核菌菌丝发生畸变,出现囊泡、甚而裂解。由此可知,菌株MX-1是一株具有良好应用潜力的防治棉花立枯病的生防菌。 相似文献
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基于不同土壤质地棉花根际微生物和酶活性特征分析 总被引:1,自引:0,他引:1
为了明确不同质地土壤对花铃期棉花根际微生物数量与酶活性的影响,采用池栽方式,以‘鲁研棉21’为材料,研究不同质地土壤(砂土、壤土、粘土)种植棉花在花铃期根际细菌、真菌、放线菌的数量及磷酸酶、脲酶和蔗糖酶的活性特征。结果表明,随着花铃期棉花的生长发育,3种质地土壤的根际微生物数量和酶活性均呈低-高-低动态变化的单峰曲线,其峰值分别出现在发育最盛的盛花期和盛花期后11 d。在土壤微生物数量方面,砂土整个花铃期3种微生物数量均显著或极显著低于壤土和粘土;而壤土中的微生物数量仅在初花后11 d低于粘土,其他时段均高于粘土。酶活性方面,砂土整个花铃期3种酶活性均显著或极显著低于壤土和粘土;壤土在初花至花后22 d时高于粘土,其余时段低于粘土,但差异均不显著。综上,棉花花铃期根际微生物活性受生长发育进程和土壤质地的双重影响。研究为棉花生产合理布局提供依据。 相似文献