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噬菌体技术在水稻白叶枯病预测上的应用 总被引:1,自引:0,他引:1
在1973~1979年间,以六合县农科所为基点,研究了测定田水中噬菌体数量的消长来预报水稻白叶枯病。病田噬菌体数量变化的趋势是:早期的田水中很少测得噬菌体,到分蘖末期其数量急剧增加(急增期),以后随病害的发展而增加,到生育末期又逐渐下降。田水中噬菌体的数量达到每毫升500个时作为“急增期”的指标,这时距田间病害的始发期有10天左右,根据噬菌体急增期可以预报病害的始发期。同时,发病田块的噬菌体在急增期的数量一般都达到或超过每毫升1000个,低于这个量的田块一般不发病。根据田水中噬菌体的数量消长,可以预测特定田块在将来是否发病。 相似文献
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水稻白叶枯病是我县主要病害之一,在沿河低洼地区发病普遍,损失严重。为了提高白叶枯病药剂防治效果,我们于1979—1981年在老病区石鼻乡古楼村用噬菌体法进行发病预测,现将结果简报如下。一、噬菌体数量与病害发生关系1.当测得每毫升田水中噬菌体数量为 400个左右后约过一星期田间可以出现中心病株,此时,田水中噬菌体数量增至每毫升800个。田间始病后,噬菌体数量随病害的发展而增加。此地晚稻有两个发病高峰,第 相似文献
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噬菌体技术在江汉稻区水稻白叶枯病预测上的应用 总被引:1,自引:0,他引:1
通过系统测定田水中噬菌体数量的变化规律和噬菌体数量的田块分布规律发现:江汉平原混栽稻区,在目前的种植品种结构下,无论是早稻田还是中稻田,将田水中噬菌体数量达到1000pfu/ml(噬菌斑/毫升)作为急增期数值阈值较为合适。从田水中噬菌体数量达到1000Pfu/ml的日期到该田块发生白叶枯病的始病期的期距为15天左右。当田水中噬菌体数量第1次超过1000pfu/ml时,大量取样测定田块中噬菌体数量的分布情况,此时田水中噬菌体数量超过1000pfu/ml的田块数占测定田块总数的百分率与稻田乳熟期病田率呈显著相关。据此可对白叶枯病的发生期和发生程度进行短期预测。1993和1994年的预测结果与实际情况相符。 相似文献
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小麦赤霉病中期预测的研究 总被引:1,自引:0,他引:1
小麦穗期赤霉病是涪陵地区小麦的主要病害之一。近几年来,流行频率增高,为害逐年加重,1975年病害流行,全区发病面积14万余亩,约占当年小麦面积的10%,损失小麦328万斤;1977年病害再度流行,全区发病面积达76万余亩,占当年小麦面积的32.4%,损失2700万斤,平均每亩减产23.3%。 为给小麦赤霉病的中期预测提供依据,近几年来,我们在我校农场与涪陵县世忠公社设置预测圃,预测大田时对小麦赤霉病流行的几个主要因素,包括小麦扬花期、田间稻茬带菌量动态、空中孢子的消长情况、病害的始病期、流行程度以及病害对小麦的影 相似文献
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小麦赤霉病流行预测初步研究 总被引:2,自引:1,他引:1
对1952—1963年病害流行程度与穗期气象要素之間的相关性测定結果表明,各年发病程度与4月下旬至5月下旬(小麦抽穗至糊熟)特別是5月上中旬(小麦开花至灌浆初期)的降雨日数、相对湿度呈明显的正相关;与同期的降雨量、平均气温相关不显著。稻桩上产生的子囊壳是本地区初侵染的主要来源,初侵染的数量和流行程度有关,其数量积累决定于雨湿条件。小麦开花灌浆初期最易感病,此时期降雨日数是病害流行的决定性因素。根据十二年資料分析結果,病害流行可以分为六种类型:早期发生型;中期发生型;后期发生型;少雨限制型;低温限制型;生育提早限制型。根据1957—1963年預测圃小麦开花后二旬內的降雨日数与发病率的相关,以发病率为应变量求出迴归方程式:Y=6.61 X—48.35,为中期預測提出雨日指标。 相似文献
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仙居县地处括苍山麓 ,是典型的山区县。水稻细条病发生始见于 1 987年 ,现已上升为杂交水稻的主要病害。杂交中晚稻常年发生面积占种植面积的70 %以上。一般田块损失 5%~ 2 0 % ,重病田块损失3 0 %~ 40 % ,且病害发生有不断加重的趋势。为进一步开发和做好水稻细条病的综合治理工作 ,我们对该病发生流行的因子及防治技术进行了较系统的调查和研究 ,现将结果报道如下 :1 流行因子分析1 .1 病源(1 )初侵染来源 :带病种子和病稻草是该病的主要初侵染来源。其中带病种子既是初侵染源 ,又是该病远距离传播的重要途径之一。我县细条病始见于 1… 相似文献
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采用GPS和GIS定位、系统监测和普查等方法,首次明确了南充市稻瘟病的流行区划和精准勘界,探明了19年来稻瘟病始见期和始见地(初始侵染源)、流行高峰期和趋势等特点。明确了南充市水稻稻瘟病发生始见期与发生程度的关系,即始见期越早,重发可能性越大;稻瘟病在田间存在4个流行高峰期,其中第1个流行高峰期发生面积对当年病害流行起着决定作用,5月底的累计发生面积与年发生面积成正相关,相关系数为0.817 2。导致稻瘟病重发的内因是水稻品种抗稻瘟能力的降低或丧失、稻瘟病病菌致病力强的生理小种增加与更强致病力的小种出现;外因是温度适宜和阴雨寡照偏多。 相似文献
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Precipitation, a natural feature of weather systems in the Earth, is vitally important for the environment of any region. Under global climate change condition, the characteristics of precipitation have changed as a consequence of enhanced global hydrological cycle. The source region of the Yellow River(SRYR), locating within the Qinghai-Tibet Plateau, is sensitive to the global climate change due to its complex orography and fragile ecosystem. To understand the precipitation characteristics and its impacts on the environment in the region, we studied the characteristics of rainy days and precipitation amount of different precipitation classes, such as light(0–5 and 5–10 mm), moderate(10–15, 15–20 and 20–25 mm) and heavy(≥25 mm) rains by analyzing the precipitation data of typical meteorological stations in the SRYR during the period 1961–2014, as well as the trends of persistent rainfall events and drought events. Results showed that annual average precipitation in this area had a non-significant(P>0.05) increasing trend, and 82.5% of the precipitation occurred from May to September. Rainy days of the 0–5 mm precipitation class significantly decreased, whereas the rainy days of 5–10, 10–15, and 20–25 mm precipitation classes increased and that of ≥25 mm precipitation class decreased insignificantly. The persistent rainfall events of 1-or 2-day and more than 2-day showed an increasing trend, with the 1-or 2-day events being more frequent. Meanwhile, the number of short drought periods(≤10 days) increased while long drought periods(>10 days) decreased. Since the 0–5 mm precipitation class had a huge impact on the grasslands productivity; the 5–10, 10–15, and 20–25 mm precipitation classes had positive effects on vegetation which rely on the deep soil water through moving nutrients and water into the root zone of these vegetation or through the plant-microbe interactions; the ≥25 mm precipitation class contributed to the floods; and more persistent rainfall events and fewer long drought events inferred positive effects on agriculture. Thus, these results indicate grassland degradation, less risk of floods, and the upgrading impact of climate change on agriculture. This study may provide scientific knowledge for policymakers to sustain the eco-environmental resources in the SYSR. 相似文献
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Aerial spore concentration of Uncinula necator (the causal agent of grape powdery mildew), weather data and cropping practices were monitored during two consecutive seasons in two vineyards of the Bordeaux area. During days with no rain, spore dispersal was mainly diurnal and showed variations that followed the same pattern as that of wind speed, and a reverse pattern to that of relative humidity. Light falls of rain, of approximately 2 mm, coincided with increased spore densities in the air. Pesticide sprays using high pressure equipment generated high wind speeds at the canopy level. This may trigger high spore dispersal. High conidial stocks were produced under spontaneous conditions in the canopy. These stocks were released only under particular events, such as heavy rains, or pesticide applications with high pressure sprayers. Other cropping practices causing leaf shaking, such as pruning, may enhance spore dispersal. Over the observation period, the onset of spore dispersal was observed during a period with no rain following a rainy period, suggesting the detrimental effect of rains on epidemic onset. Epidemiological and disease management implications are discussed. 相似文献
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试验结果表明,本菌(Stemphylium vesicarium(Wallr.) Simons)以病残体上分生孢子和菌丝体在田间和冷藏室越冬,9月至翌年6月检查,分生孢子萌发率为16.4~41.3%。人工接种试验指出,不论有无伤口,病菌均可侵染大蒜,但洋葱与大葱在伤口接种条件下病情较重。在自然条件下,大蒜的斑点型病状出现于6月下旬,7月为病情高峰期。影响病情的天气因素,主要是7月份温度和7月中旬的降水量(r=0.69)。如果7月雨次多、雨时长,病情即极为严重,可导致蒜田绝收。化学防治试验结果,以腐霉利防效最佳。从7月上旬开始,每间隔10~13天喷药1次。喷药2~3次即可取得较好的防治效果。 相似文献
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本文介绍了灰色系统理论的重要部分,灰色关联度分析的原理和方法,分析了射阳县1973-1984年蚕豆赤斑病流行系统。结果表明菌源、4月中旬雨日数、上年11月至下年1月的雨日数和4月上中旬露日数是影响蚕豆赤斑病流行势的主导因素。变异系数和方差分析证明了灰色关联度分析的结果是正确、可靠的,该结论与客观实际一致。从而否定了"菌源不是影响蚕豆赤斑病发生的主导因素,,的观点。因此,在预测蚕豆赤斑病流行趋势时,首先务必考虑上述主导因素。这种新的数学方法比其它任何方法都更简易、方便和有效。另外,本文还讨论了灰色关联度分析与相关分析结果不一致的原因,以及灰色关联度分析在其它植病流行系统分析中应用的可能性和注意点。 相似文献
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Akira Kawaguchi 《Journal of General Plant Pathology》2014,80(5):435-442
Bacterial spot, caused by Xanthomonas arboricola pv. pruni, is the most important disease that affects peach production in Okayama Prefecture, Japan. Currently, this disease is managed mainly with copper compounds applied at two stages, before flowering and after harvesting, or with antibiotics applied in May and June. Here we identified the disease risk factors that affect peach at harvest and developed a disease-forecasting model to help growers decide when to apply bactericides. The model was based on parameters for weather data collected for September and October of 2001 through 2012 and for April, May, and June of 2002 through 2013, combined with data on bacterial leaf spot incidence obtained from 28 to 30 fields per year in August from 2001 to 2012 and in May to July from 2002 to 2013. The model, developed using a logistic regression analysis, included the percentage of fields with a bacterial spot incidence (BSI) ≥1 % in mid-August of the previous season and the number of rainy days (≥5 mm/day) during the current June as predictors, and explained 75.0 % of the variability. These results suggest that the previous season’s BSI and weather variables in the present season can be used to predict the risk of bacterial spot. 相似文献
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根据河南、河北两省多年多点对玉米小斑病流行进程的观察记载,共积累20个年次的病情系统调查资料,结合相应的气象数据,按照本病的流行规律,设计8个供选因子,用北京大学DJS-18型电子计算机进行逐步回归运算,分别推导出从7月中旬至8月中旬的30天中期预测式和从7月中旬至9月中旬的60天长期预测式。
所谓测报时间范围内相应时期的气象因素,在中期预报中为7月份的总雨量、总雨日、日平均温度等,在长期预报中为7、8两个月的上述气象因素。
两个预报式的确定系数分别为0.8125和0.6843,经用建立模型以外的多个实际病情对所得方程式进行检验,证明预测式有较高的可靠度。
长期预报式可用做流行强度的趋势性预报,中期预报式可供确定防治适期的参考。 相似文献
所谓测报时间范围内相应时期的气象因素,在中期预报中为7月份的总雨量、总雨日、日平均温度等,在长期预报中为7、8两个月的上述气象因素。
两个预报式的确定系数分别为0.8125和0.6843,经用建立模型以外的多个实际病情对所得方程式进行检验,证明预测式有较高的可靠度。
长期预报式可用做流行强度的趋势性预报,中期预报式可供确定防治适期的参考。 相似文献
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ABSTRACT Severe Cercospora leaf spots epidemics in sugar beet during the late 1980s and early 1990s in southern Germany prompted us to initiate investigations on the epidemiology of the causal agent, Cercospora beticola. The data set involved 69 field trials (1993 to 2003) focusing on factors affecting the epidemic onset of this disease. Observations were made at weekly intervals, recording the calendar week when canopy closure occurred (growth stage according to BBCH scale = 39) and symptom development by assessing the percentage of infected leaf area on a single-leaf basis (n = 40 plants). These monitoring trials revealed that epidemic onset varied between early July and mid-September. Hence, the target was to identify the reasons for this variation in order to deduct the most suitable approach for predicting epidemic onset. Differences in cultivar resistance explained part of epidemic onset variability, as did different timings of canopy closure, presumably due to associated microclimate changes. Moreover, meteorological variables were considered as potential reasons for variation in epidemic onset. The weather-dependent infection probability was assessed by daily infection values (DIV) in the range from 0 to 1 using hourly weather data. For calculating DIVs, the temperature effect was quantified by the proportions of the latent period (LP) relative to the optimum at 20 to 25 degrees C, established by artificial inoculation of sugar beet plants in growth cabinets. Artificial infection experiments further established that air relative humidity (RH) >95% or leaf wetness was required for infection and subsequent lesion development. Under field conditions, the probability of leaf wetness was 75% at RH >90%. Therefore, DIVs were set to 0 for RH =90% in the absence of precipitation (moisture index I). Alternatively, the effect of moisture was modeled with a sigmoidal function describing the occurrence of leaf wetness in dependence of RH in the field (moisture index II). Using this approach, DIV values were cumulated (c-DIV) for each of the 69 trials beginning either at fixed starting dates (1 May, 16 May, or 1 June) or the dates of canopy closure. Accumulation of DIV ended at the time of epidemic onset. The two different moisture index definitions had no significant influence on c-DIV; whereas, for starting time of summation of DIV, the date of canopy closure was more suitable. Values of c-DIV ranged from 7 to 19 in highly susceptible cultivars and 12 to 25 in cultivars with lower susceptibility. Given this variation, c-DIV values were insufficient to explain differences in the date of epidemic onset and thus were not considered suitable for making accurate and precise management decisions. However, a negative prognosis assessing the most likely periods of disease absence was possible by determining the minimum c-DIV as a threshold. This threshold was 7 c-DIV for highly susceptible cultivars and 12 c-DIV for cultivars with low susceptibility. Crop monitoring is recommended as soon as these threshold values are exceeded so that the exact epidemic onset time can be observed. 相似文献
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A simple forecasting model for Septoria spp. in winter wheat was developed based on historical data (1980–89) including precipitation, growth stage, disease severity and yield response to fungicide treatments. The number of days with precipitation ≥ 1 mm, calculated during a 30-day period starting at the beginning of stem elongation (GS 32), correlated well with attacks of Septoria spp. later in the season and with the yield response in trials with fungicide treatments. Seven or 8 days with rainfall ≥ 1 mm was suggested as a threshold for Septoria treatment. Model development and possible further improvements are discussed. 相似文献