应用模糊图的最大树聚类法预测小麦白粉病的流行程度

本文利用郯城县6年小麦白粉病资料,并选取了与郯城县小麦白粉病流行程度关系密切的前一年6月份降水量、3月份日平均相对湿度、3月份日照时数和3月下旬雨日等气象因素作为预报因子,应用模糊图的最大树聚类法对小麦白粉病流行程度中期预报进行了初步探讨。首先将包括预报样本(1991     

甘肃中部麦区小麦条锈病菌越夏调查及品种抗性变异监测结果初报*

2007-2009年,对甘肃省中部麦区小麦条锈病越夏情况进行调查,结果发现：条锈病菌在定西、临夏等中部麦区海拔1 718~2 350 m地带自生麦苗上可顺利越夏,病田率和病叶率分别为63.0%~80.0%和1.05%~5.80%,其越夏菌源量比陇南更大,是当地秋苗发病的初侵染源;秋苗病情调查结果表明,中部麦区秋苗病田率和病叶率均高于同期陇南麦区;品种抗性监测结果发现,34个供试品种（系）在中部麦区和陇南麦区的抗条锈性表现基本一致,部分品种发病程度重于陇南麦区。表明甘肃省定西、临夏等中部麦区已成为陇南小麦条锈病越夏区的重要组成部分。文中还对中部麦区越夏菌源的影响、作用及品种抗性变异因素等进行了讨论。     

甘肃河东地区小麦条锈病(Wheat Stripe Rust)越夏指标的修订

小麦条锈病越夏气象指标,目前仍沿用二十世纪六十年代的研究结果,需要修订完善。文中利用甘肃河东地区2007-2014年50个不同海拔高度小麦条锈病单点病田率、病情指数调查资料、39个平均越夏病田率资料,采用统计学方法建立了小麦条锈病病情指数、平均病田率的气象统计模型,综合两种方法计算结果,确定了甘肃河东地区小麦条锈病越夏指标的上限为夏季最热时段8d滑动平均气温24~25℃,期间空气相对湿度越低对应的平均气温也越低。研究为当地准确发布中短期趋势预报,积极开展早期防治,控制病害越夏范围具有一定指导意义。     

2007年荆州市小麦白粉病发生特点及防控对策

小麦白粉病是荆州市小麦上的一种常发性病害,但每年发生的程度年度间差异较大。2007年由于气候条件有利病害发生,加之种植的小麦主要品种对白粉病的抗性较差,导致2007年小麦白粉病大发生。据统计,全市小麦白粉病发生面积6.91万hm2次,防治面积10.17万hm2次,挽回损失2.15万t,实际损失1.43万t。1发生特点1.1见病早据系统调查观测,小麦白粉病于1月11日见病,比历年平均提早45d左右,比2006年早近2个月,属偏早的年份。1.2扩展快3月12日调查,病田率为66.7%,平均病株率33.2%;3月28日调查,病田率上升为100%,平均病株率70.2%,平均病株率是3月12日的2.1…     

陇南小麦条锈病越夏菌量对流行的影响研究初报

通过对1989～2000年陇南小麦条锈病越夏调查资料统计分析,明确了越夏菌量与越夏区7～8月降水量密切相关,越夏菌量与秋苗发病及来年流行程度相关显著.组建了以越夏菌量预报来年流行程度的长期预测模型.     

豫西南麦区小麦条锈病中期测报技术研究

通过对连续26年系统测报资料分析研究,明确了豫西南麦区小麦条锈病流行程度与小麦品种抗性状况、早春菌源基数、3月下旬至5月上旬雨日、雨量、雾露日、平均气温等气象条件关系密切.提出了病害中期预测的综合分析预测法和预测指标,选择4月上旬末病田率、4月份降水系数和4月中旬至5月上旬日均温.建立了病害发生程度预报武,历史回测拟合准确率达95.4%,2007～2008年预测检验,表明预报结果与发生实况相一致.     

小麦赤霉病综合预报方法初探

1981～1988年进行了小麦赤霉病综合预报方法研究,1987年以来应用证明,预报结果较好,对指导大面积综合防治起了明显作用。1.病害流行与预报要素:据多点系统观察和大面积普查结果表明:流行程度与4月下旬～5月中旬的雨日、雨量、连阴雨次数、相对湿度、玉米茬带菌率均呈正相关,与日照呈负相关。并与上年9月和11月总雨量呈正相关,与上年7、8月气温呈负相关。2.综合预报方法:长期预报每年1月初做出,如上年7、8月均温低于26℃,9、11月总降雨     

第3代稻飞虱主要气象影响因子的通径分析及预测

研究气象因子对第3代稻飞虱发生、发展的影响,为稻飞虱的预报和防治提供科学依据.利用广东省化州市1993~2010年稻飞虱系统调查资料和气象资料,对第3代稻飞虱发生程度与主要气象因子进行相关和通径分析,建立回归预测模型.结果表明:上年8月下旬平均最高气温和当年1月上旬相对湿度是影响第3代稻飞虱发生程度的主导因子,上年8月下旬至9月中旬平均气温的直接作用次之,上年12月中旬至下旬降雨量、上年8月下旬温湿系数等对害虫发生程度的直接作用较小,但通过上年8月下旬平均最高气温发挥间接作用.利用逐步回归方法建立了第3代稻飞虱发生程度的预测模型,模型历史拟合准确率为87.8%,而2011年预测结果与实际发生实况一致.生产中可以应用拟合的模型对稻飞虱的发生为害进行预测预报.     

早稻纹枯病流行温湿度的综合指标探讨

水稻纹枯病的流行程度受气候因子温湿度的制约,本文选出影响早稻纹枯病流行的5个温湿度因子:上年10～12月平均气温(x_1)、当年5月下旬平均气温(x_2)、当年3～5月平均相对湿度(x_3)、当年6月平均气温(x_4)和当年6月平均相对湿度(x_5),用模糊数学求综合隶属度法,作为早稻纹枯病流行温湿度的综合指标,能反映温湿度对本病流行程度的影响,拟合率达90%。如用3个因子 x_1、x_2、x_3对早稻纹枯病进行预测,回测结果与实测     

气候异常对青海湖环湖地区草地蝗虫灾害发生的影响

采用合成分析和相关分析方法研究了气候异常对青海湖环湖地区草地蝗虫灾害发生的影响。合成分析表明蝗虫灾害严重与当年气候状况关系密切。蝗灾等级与前一年7～8月平均气温、当年2～8月月平均气温、冬季降水量呈正相关 ,而与前一年7～9月降水量、10～12月气温、当年5～9月降水量呈负相关关系。这说明前一年和当年夏季温暖少雨、冬季多雪有利于蝗虫生长发育和越冬 ,会造成蝗灾 ,相反则不会发生     

Surveys of cereal diseases and pests in the Netherlands. 4. Occurrence of powdery mildew and rusts in winter wheat

Results of annual surveys of winter wheat fields from 1974 to 1986 were compiled to describe epidemics of powdery mildew and rusts in relation to weather and cultivar resistance.An average of 29 and 70% of fields were infected by powdery mildew in May and July, respectively. Mildew prevalence in May was positively correlated with average temperature in October and with average temperature over the months December, January, February and March. In addition, it was correlated negatively with the average grade of mildew resistance of the cultivars sown each year. Prevalence of mildew in July did not show consistent correlations with weather characteristics nor with mildew prevalence in May.Yellow rust was usually not detected in May and on average 18% of the fields was infected in July. The occurrence of yellow rust decreased after 1977, when the farmers adopted cultivars resistant or moderately resistant to yellow rust.Brown rust was usually not detected in May, while in July on average 48% of the fields was infected. Brown rust intensity in July was high in years with a high March temperature and high precipitation during April and May.Black rust was rare in the Netherlands, with 3 and 1% of the fields infected in July 1977 and 1981, respectively.     

豫北麦区小麦白粉病中期测报技术研究

通过对小麦白粉病１４ａ的发生情况研究分析，初步明确影响豫北麦区小麦白粉病流行的主要因素和主要预测因子是当年早春３月中旬的菌源基数、３～４月份降水量和日照时数，提出了病害中期预测的综合分析预测法和预测指标，建立了病害发生程度预测式，经１９９４～１９９５年预测检验，表明预测结果与发生实际基本一致     

新疆泽普县小麦白粉病流行的时间动态及预测模型

2012年-2019年对泽普县春季小麦白粉病田间发生情况进行了系统调查, 并对数据进行了分析和模型拟合, 明确了当地白粉病春季发生和流行的特点?其病害春季流行曲线为典型的单峰S形曲线, 符合Logistic或Gompertz模型?在此基础上, 通过Pearson相关系数法分析了多年来该地小麦不同生育期白粉病病情指数与66个主要气象因子之间的相关关系, 筛选出影响小麦白粉病发生流行的关键气象因子为1月下旬平均日照时间?2月下旬平均气温?1月上旬-3月上旬平均气温和10月下旬-4月中旬平均日照时间, 并采用多元回归分析法建立了基于关键气象因子的小麦扬花期?灌浆初期和灌浆中期的病害预测模型?此研究结果可为当地小麦白粉病的防控提供技术支撑?     

河北省小麦白粉病发生程度的中期预测

根据全省１０个县（市）９ａ的历史资料进行归纳总结，提出小麦白粉病流行结构模型，利用３月下旬至４月中旬的气象因子（降雨量、雨日、平均相对湿度）实况值，用判别分析的方法，对当年小麦白粉病发生程度进行中期预测，经１９９３～１９９４年的应用检验，预测结果与各监测县及全省实况吻合     

河南小麦白粉病逐年春季流行时间动态

1980－1997年对河南小麦白粉病春季流行的时间动态进行了系统分析。结果表明：（1）逐年春季流行程度波动较大,中度以上流行年份有9年,但流行程度之间没有明显的周期性。（2）逐年春季流行的时间动态有明显差异,特大流行年份白粉病发病特早,指数增长期和逻辑斯蒂期比其它年份长30d以上,表观侵染速率达0.16以上;大流行年和中度流行年份的始发期相同,表观侵染速率前者达0.16,后者只有0.12-0.14;轻度流行年始发期晚,指数增长期和逻辑斯蒂期短,表观侵染速率低,导致最终病情指数低。（3）小麦越冬返青期的降水量、雨日、水份积分指数、相对湿度对白粉病的始发期有显著影响,但白粉病的最终流行程度主要取决于小麦拔节孕穗期的水份积分指数、温雨系数、降水量、雨日和温度。     

Forecasting the national incidence of sugar-beet powdery mildew from weather data in Britain

In a national survey of the incidence of powdery mildew (Erysiphe betae) in sugar beet in Britain, between 1980 and 1989, in which between 335 and 717 fields were inspected at the end of August each year, the average crop area infected ranged from 2% in 1986 to 68% in 1989. The effect of various climatic factors that might be expected to influence powdery mildew development over this period was examined, using meteorological records from Broom's Barn Experimental Station, Using simple linear regression analyses, a significant association was found between disease incidence and both air temperature and rainfall incidence in the period April-August, However, air temperature and frost incidence in some winter months were also closely associated with the incidence of powdery mildew in the following crop.
Combinations of these variables were examined in stepwise multiple-regression analyses, The model of best fit, incorporating winter frost incidence with summer temperature and rainfall incidence, accounted for 95% of the variation. Model validation procedures demonstrated the superiority of this model over those involving single variables. Nevertheless, for forecasting purposes, the best correlation was found between the crop area infected at the end of August each year and the number of days with a ground frost in the preceding February and March. This single climatic variable accounted for 82% of the variation and its potential use to forecast powdery mildew incidence in the national sugar-beet crop is discussed.     

小麦白粉病流行的IRM建模研究

 本文以温度和相对湿度为主要影响因素,根据IRM (Integrated Rate Methodology)的原理研制了小麦白粉病流行的动态模拟模型,同时对其参数进行了分析。模型模拟和预测结果表明该模型能较好地描述白粉病的流行。     

小麦白粉病菌侵染机率的研究

 在感病的小麦品种上影响白粉病菌(Ery siphe graminis f.sp.tritici)侵染机率变化的主要因素是平均温度(T)和平均相对湿度(RH)。平均温度与侵染机率的关系符合ŷ=X/(a+bX+cX²)的二次抛物线函数关系,最适温度范围在5.15-10℃之间。平均相对湿度与侵染机率的关系一般符合直线关系,最适湿度范围在81.15-97.0%之间。通经分析表明,平均相对湿度较平均温度对白粉病菌侵染机率的直接影响更大。     

Disease-weather relationships for powdery mildew and yellow rust on winter wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.     

Threshold values for chemical control of powdery mildew (Erysiphe cruciferarum) on Brussels sprouts

To establish control thresholds for chemical control of powdery mildew (Erysiphe cruciferarum) on Brussels sprouts, mildew intensity on leaves and buds was observed on the cultivars Lunet, Tardis and Asgard during three years in unsprayed plots. Mildew infection on the leaves was observed from late August onwards, increasing to moderate or high levels. In one year light infestation of the buds was observed, but no reduction in quality occurred. These preliminary results indicate, that from late August onwards the following levels of leaf injury by powdery mildew can be tolerated: T=5+0.42^*(Julian date — 235), in which T is the tolerable leaf injury in percentage leaf area covered. When sampling the crop to assess powdery mildew infection, care must be taken that leaves are sampled from all stem positions, as top leaves tend to be much less infected.