共查询到20条相似文献，搜索用时 31 毫秒
1.
Xiang-Ming Xu 《European journal of plant pathology / European Foundation for Plant Pathology》1999,105(1):13-21
The effect of temperature on the length of the incubation period of rose powdery mildew, caused by Sphaerotheca pannosa var. rosae, was studied. At constant temperature over the range 8–28°C, the length of the incubation period ranged from 3 to 10 days; no visible colonies developed at 30°C after 19 days. The relationship between temperature and the rate of development of mildew colonies within the incubation period under constant temperature was described by two alternative non-linear models (exponential and thermodynamic). The resulting curves were asymmetrically bell-shaped with an optimum temperature of c. 23°C. The two constant-temperature models predicted the development of powdery mildew under fluctuating temperatures with similar accuracy, even though the exponential model fitted the constant temperature data less well than the thermodynamic model. The thermodynamic model failed to fit the fluctuating-temperature data directly, whereas the exponential model fitted those data directly and the fit was similar to the corresponding model from the constant-temperature data. Fitting the models to the combined (constant and fluctuating temperature) data gave results that were nearly identical to those based on the constant-temperature data alone. 相似文献
2.
X-M. XU 《Plant pathology》1996,45(5):924-932
The effects of constant and fluctuating temperatures on the incubation period of apple powdery mildew, caused by Podosphaera leucotricha , were studied. At constant temperatures, incubation periods ranged from 3 to 12 days over temperatures 8°C–30°C, and no visible lesions developed at 32°C. A nonlinear model was developed to describe the relationship between temperature and the rate of mildew colony development. The resulting curve is bell-shaped with an optimum temperature at about 23°C. When this model was used to predict mildew development under fluctuating temperatures at an integration step of 48 min, however, it consistently overestimated development rate for fluctuating periods with average temperatures higher than 20°C. A nonlinear model was also fitted directly to the fluctuating temperature data, thus taking into account the nonlinear effect. The overestimation of development rate by the constant model for high temperatures was confirmed when the two models were compared. This overestimation probably resulted from differences in the levels of relative humidity between constant and fluctuating temperature regimes. Possible practical use of the model is discussed. 相似文献
3.
通过对储存玉米霉变初期的感官症状观察、分离菌的PCR检测及在不同环境条件下的生长预测模型建立,探讨了识别、预防储存玉米发生黄曲霉毒素及其主要产生菌污染的实用方法。结果表明:籽粒色泽及致密性改变、表面有潮湿感、粮堆内局部发热等症状的出现可表征储存玉米有可能发生真菌污染。以毒素合成相关的全局性调控因子veA基因为靶标,对污染玉米样品分离菌进行PCR检测,扩增出约1.9kb的条带,与预期大小相符,证明污染菌是黄曲霉或寄生曲霉。污染曲霉在不同玉米水分活度和环境温度下的生长数据,经Baranyi函数拟合、估测其最大生长速度,并建立了生长速度随玉米水分活度和环境温度变化的多项式回归模型;模型显示玉米水分活度和环境温度对污染曲霉的生长影响具有协同性;要确保储存玉米安全,储存参数的限值选择应远离适合污染菌生长的区域。本研究为储存玉米安全管理决策、玉米水分活度和环境温度限值的选择及调控提供支持,利于降低储存玉米的黄曲霉毒素及其主要产生曲霉(黄曲霉或寄生曲霉)的污染风险。 相似文献
4.
The successful development of phenology models from field studies depends on many factors, some of which are entirely under the control of pest managers. For example, one such factor is the choice of method for calculating thermal units. In this study, we have demonstrated that four methods for calculating thermal units provided for acceptable predictions of one phenological event of one insect species, while another method for calculating thermal units did not. The measure of central tendency (mean or median) that is used to estimate lower developmental temperatures and required thermal summations is another factor that pest managers can control when developing phenology models from field studies. Here, we show that predictions that were made when using phenology models based on median lower developmental temperatures and median required thermal summations were superior to predictions that were made when using phenology models based on mean lower developmental temperatures and mean required thermal summations. The use of bootstrap vs. non-bootstrap estimates of lower developmental temperatures and required thermal summations is yet another factor that pest managers can control when developing phenology models from field studies. In this study, we found that calculating and using bootstrap estimates of lower developmental temperatures and required thermal summations in phenology models did not improve the predictions of one phenological event for one insect species. The implications of these and other findings are discussed. 相似文献
5.
Modelling weed seedling emergence pattern appears to be a promising approach in the development of effective weed management programmes based on the selection of optimal timing of control operations. Thermal and hydrothermal time models propose that seed germination rates are proportional to the amount by which temperature and water potential exceed threshold values for these environmental factors. Hence, base temperature for seed germination is a fundamental biological parameter for the prediction of weed emergence. A series of laboratory experiments were conducted to estimate base temperature in three weed species belonging to the Asteraceae family, predominant in conservation tillage fields in north‐eastern Italy. The traditional method based on germination assays at constant temperatures was compared with a method based on assays at alternating temperatures. The latter might represent an alternative to the former for those species which do not germinate or only poorly under constant temperatures. Base temperature was estimated by regressing the reciprocal of the median germination time on temperature comparing two functions, a broken‐stick and an exponential‐type model. Both models showed good fit to all data in the whole temperature range and in almost all cases provided similar estimates of base temperature. The main result is that, for the weed species examined in this study, the use of alternating temperatures for base temperature estimation appears to be possible. However, further research is required to test if the use of germination assays performed at alternating temperatures can be a suitable method to estimate base temperature of species that have too low germination at constant temperatures. 相似文献
6.
温度与昆虫内禀增长率关系模型的比较 总被引：2，自引：0，他引：2
数学模型可用于反映温度对昆虫生长速率的动态变化,为选择一个对害虫发生预测具有重要意义的通用性模型,选择Beta、Briére、Ratkowsky和Lobry-Rosso-Flandrois(LRF)4个非线性模型分别对8组不同温度下昆虫和螨类内禀增长率数据集进行拟合,并比较模型拟合效果的优劣。结果表明:Ratkowsky模型对8组数据的拟合优度总体表现最好,其次为LRF模型和Beta模型,而Briére模型表现欠佳;Ratkowsky模型对低温阈值和高温阈值的估计较其它3个模型更为可靠。Ratkowsky模型不仅可以用于描述温度对细菌种群增长速率的影响,还可应用于描述温度对昆虫和螨类内禀增长率的影响。 相似文献
7.
Wetness of the host surface is a critical environmental factor for the development of foliar fungal diseases, but it is difficult to estimate the wetness durations required by pathogens for infection when only few experimental data are available. In this paper, we propose a method to estimate wetness duration requirements of foliar fungal pathogens when precise experimental data are not available. The proposed method is based on approximate Bayesian computation. It only requires lower and upper bounds of wetness duration requirements for one or fewer temperatures. We describe the method, show how to apply it to an infection model, and then present a case study on Mycosphaerella nawae, the causal agent of circular leaf spot of persimmon. In this example, the parameters of a simple infection model were estimated using experimental data found in the literature for the pathogen, and the model was applied to assess the risk in a Spanish area recently affected by the disease. The results showed that the probability of successful infection was higher than 0.5 for 32% of the on-site wetness durations recorded in the affected area. Results obtained with simulated data showed that our method was able to improve the estimation of wetness duration requirement. Given the flexibility of the proposed method, we expect it to become adopted for assessing the risk of introduction of exotic fungal plant pathogens. 相似文献
8.
Sébastien Guyader Julia Crombez Michèle Salles François Bussière Thierry Bajazet 《European journal of plant pathology / European Foundation for Plant Pathology》2013,136(3):535-545
Modelling the epidemiology of water yam anthracnose (Dioscorea alata) caused by the fungus Colletotrichum gloeosporioides is an important research goal, as it will allow the investigation of a wide range of scenarios of new practices to reduce the disease impact before experimentation in the field. Developing such a model requires a prior knowledge of the fungus’s response to the environmental conditions, which will be affected by pest management. In this work, we first measured the response of the fungus to the main physical environmental factors controlling its development, namely temperature (ranging from 18 °C to 36 °C) and wetness duration (from 2 h to 72 h). As response variables, we measured the percentage of formed appressoria (relative to the total number of spores), the length of the latent period (time lag between inoculation and first symptoms observed), and the rate of necrotic lesion extension (percentage of diseased leaf surface at different time steps). These variables allow us to estimate the effects of temperature and wetness duration on the success of infection (appressoria formation) and the subsequent rate of disease development (latent period length and lesion extension rate). The data were fitted to non-linear models chosen for their ability to describe the observed patterns. From our data and model analyses, we were able to estimate parameters such as the optimal and maximal temperatures (25–28 °C and 36 °C, respectively), the required wetness duration to reach 20 % of infection success and the time to reach 5 % disease severity as a function of temperature. 相似文献
9.
Experiments were conducted under controlled environment conditions to study the relationship between environmental conditions, development of fusarium head blight (FHB) and mycotoxin production. A single isolate from each of four Fusarium species ( F. avenaceum , F. culmorum , F. graminearum and F. poae ) was used to inoculate wheat ears separately. Combinations of two or three isolates were also used to inoculate ears simultaneously. Inoculated ears were subjected to various combinations of duration of wetness (6–48 h) and temperature (10–30°C). For all inoculations, both incidence of spikelets with FHB symptoms and concentration of mycotoxins generally increased with increasing length of wetness period and temperature. There were significant positive correlations among disease incidence, fungal biomass (quantified as total amount of fungal DNA) and mycotoxins. Mycotoxin production was also greatly enhanced by high temperatures (≥ 20°C) during initial infection periods. In single-isolate inoculations, F. poae was the least aggressive. There was no evidence to support synergetic interactions between fungal isolates in causing visual symptoms; rather the results suggest, in most cases, the presence of competitive interactions. Furthermore, the competition led to large reductions in fungal biomass compared to single-isolate inoculations, often > 90% reduction for the weaker isolate(s). In contrast, mycotoxin productivity increased dramatically in the co-inoculations, by as much as 1000 times, suggesting that competition resulted in greater production of trichothecene mycotoxins. The F. graminearum isolate was most competitive and isolates of the other three species were similar in their competitiveness. 相似文献
10.
Xu 《Plant pathology》1999,48(5):662-667
The effects of temperature on the length of the latent period of rose powdery mildew, caused by Sphaerotheca pannosa var . rosae , were studied. At constant temperatures over the range of 10–28°C, the length of the latent period ranged from 4 to 10 days. The relationship between temperature and the rate of fungal development during the latent period (expressed as the reciprocal of the latent period) was described by a nonlinear (thermodynamic) model. The resulting curve was asymmetrically bell-shaped with an optimum temperature of about 22°C. The latent period was further subdivided into two periods: incubation period (from inoculation to visible colonies) and postincubation period (from visible colonies to the first sign of conidiophores). The relationship between temperature and the rate of fungal development during the incubation period (expressed as the reciprocal of the incubation period) was also well described by a thermodynamic model. In contrast, the relationship between temperature and the rate of fungal development during the postincubation period (expressed as the reciprocal of the postincubation period) was approximately linear. The latent period under fluctuating temperatures was predicted using a two-stage integration scheme at a step of 24 min by first integrating the incubation rate and then the postincubation rate. The predicted length of the latent period agreed well with the observed values. 相似文献
11.
The forecasting tool SOPRA has been developed with the objective of optimizing timing of monitoring, management and control measures of insect pests in fruit orchards in Switzerland. Applying time‐varying distributed delay approaches, phenology‐models were developed driven by solar radiation, air temperature and soil temperature on hourly basis. Relationships between temperature and stage‐specific development rates for relevant stages of the life cycles were established under controlled laboratory conditions for Dysaphis plantaginea, Hoplocampa testudinea, Cydia pomonella, Grapholita lobarzewskii, Cacopsylla pyri, Rhagoletis cerasi, Anthonomus pomorum and Adoxophyes orana. The implementation of body temperatures in the models is based on habitat selection and biophysical modelling of habitat conditions. In order to validate modelling, phenology predictions were compared with several years of independent field observations. On the basis of local weather data, the age structure of the pest populations is simulated and crucial events for management activities are announced. Through a web interface, the simulation results are made available to consultants and growers ( http://www.sopra.info ) and the latter can be applied as a decision support system for the eight major insect pests of fruit orchards in the alpine valleys and north of the Alps on local and regional scale. 相似文献
12.
The effects of temperature on the length of the incubation and latent periods of hawthorn powdery mildew, caused by Podosphaera clandestina , were studied. At constant temperatures over the range 10–28°C, the incubation period ranged from 5 to 14 days and the latent period from 5 to 16 days; no visible colonies had developed at 30°C after 15 days. The relationships between temperature and the rates of fungus development within the incubation and latent periods were well described by a nonlinear model. The resulting curves were asymmetrically bell-shaped with an optimum temperature of approximately 23°C. The lengths of the incubation and latent periods under fluctuating temperatures were also determined, and were used to evaluate the models developed from constant temperature experiments for their accuracy of prediction. The incubation and latent periods under fluctuating temperature regimes were predicted using a rate-summation scheme with a time step of 24 min, by integrating the respective incubation and latent rate functions obtained under constant temperatures. The predicted incubation or latent periods agreed well with the observed values. Under constant temperature the interval between the times when symptoms and sporulation on the same leaflet were first observed was very short, on average <1 day, and was not significantly correlated with temperature. However, this interval was negatively correlated with mean temperature under fluctuating regimes. 相似文献
13.
The mode of reproduction of the Indian population ofAphelenchoides besseyi was studied under different temperatures and on different fungal species used for culturing the nematode. Although parthenogenetic
reproduction in this species was recorded on all the fungi tested, the influence of the different fungal species on development
and population buildup varied. There was a significant increase in nematode fecundity when one or two males were placed along
with single females in the medium, as compared with when no male was introduced. Increasing the number of males further to
eight depressed fecundity as compared with the treatment with two males. 相似文献
14.
A.W. Schaafsma R.W. Nicol L.M. Reid 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(8):737-746
An integral component of breeding maize for resistance to Fusarium graminearum ear rot is the identification of resistant genotypes. Since natural infection is not consistent from year to year, maize researchers must use manual techniques to inoculate the plant material with fungal spores. Information is presented here on site resistance of commercial maize hybrids to F. graminearum over three years and at two locations. Additionally, results of an investigation on the two predominant techniques of inoculating maize, the silk channel and kernel inoculation methods, are reported. Of 61 commercial hybrids tested, only two were ranked as moderately resistant to the fungus by both inoculation methods. These two hybrids also had a stable response to the F. graminearum infection across seven environments when the silk channel inoculation method was used. The majority of the hybrids were ranked as either susceptible or highly susceptible and less than 10% of the hybrids had a stable response to fungal infection. In the investigation of methodology, it was concluded that silk browning would be the least laborious way to identify the ideal time to complete silk channel inoculations. It was found that kernel inoculations using the pin inoculation method should take place between 11 and 15 days after 50% silking to achieve proper hybrid discrimination. Mist irrigation increased mold severity ratings and resulted in greater discrimination between hybrids with varying levels of resistance to F. graminearum infection. 相似文献
15.
Maize production in temperate countries is threatened by late wilt, caused by Magnaporthiopsis maydis. Plant infection occurs early after sowing, but symptoms appear from flowering onwards. The disease is mainly controlled by genetic resistance, which is often partially expressed in the field. Development of disease symptoms is also highly dependent on environmental conditions. This study looked at whether production and growth of susceptible maize are affected by M. maydis under environmental conditions that are suboptimal for disease development. In addition, the effect of water availability on disease development under optimal conditions was determined. Pot experiments were conducted in an open-air enclosure in 2013, 2015 and 2016. Under unfavourable conditions for disease (low air temperature and relatively high air humidity), aboveground symptoms did not appear in the plants despite growth and production variables being clearly altered by the fungus. When air temperatures and humidity were optimal for disease development (air temperatures relatively high and humidity rather low), leaf symptoms on inoculated plants became apparent but with secondary importance compared to decreases in growth and production. The pathogen also affected the root:aboveground biomass ratio to a greater extent when the plants were under good water conditions than under deficit irrigation. Under optimal conditions and with good soil water content, the infected crop may end its cycle without symptoms, with the disease undetected, although reductions in yield and aboveground biomass can occur. 相似文献
16.
采用体表接菌法测定了商品生物农药金龟子绿僵菌油悬浮剂PD20080671在15、20、25、30、35和40℃等6个不同温度条件下对东亚飞蝗3龄蝗蝻的致病力的影响。结果表明：东亚飞蝗3龄蝗蝻的累积死亡率在接菌后19 d内均随天数的增加而升高。35℃的累积死亡率最高（82.50%）,显著高于其他处理;40℃的累积死亡率最低,为55.00%。死亡个体的湿度培养结果显示绿僵菌在高温条件下萌发的时间较短,40℃为4.26 d,15℃为19.36 d。结果表明环境温度低于15℃或高于35℃都不利于绿僵菌杀死蝗虫。因此,在田间施用金龟子绿僵菌防治东亚飞蝗时应尽量避免高温天气,建议在上午低温时进行防治。 相似文献
17.
The effect of temperature and light after spraying on the activity of flumetsulam and metosulam when applied to seedlings of Raphanus raphanistrum was evaluated under controlled environments. Flumetsulam and metosulam were applied at 0.01–3 times the recommended doses and the plants were subjected to a range of temperatures after spraying. Herbicide activity was estimated from dose–response curves of fresh weight. Varying the temperature after spraying from 1 to 20 °C increased the activity of flumetsulam and metosulam, as determined by comparison of ED50 , by a factor of 97 and 7 respectively. Large increases in herbicide activity occurred in the 1–5 °C range and smaller but significant increases at temperatures greater than 5 °C. No significant differences in the activity of the herbicides were found when the plants were subjected to light or dark conditions at 5 °C after spraying. The influence of temperature on activity may lead to opportunities for rate adjustment of flumetsulam and metosulam based on the temperature prevailing around the time of spraying. 相似文献
18.
ABSTRACT In this study, a simple generic infection model was developed for predicting infection periods by fungal foliar pathogens. The model is designed primarily for use in forecasting pathogens that do not have extensive epidemiological data. Most existing infection models require a background epidemiological data set, usually including laboratory estimates of infection at multiple temperature and wetness combinations. The model developed in this study can use inputs based on subjective estimates of the cardinal temperatures and the wetness duration requirement. These inputs are available for many pathogens or may be estimated from related pathogens. The model uses a temperature response function which is scaled to the minimum and optimum values of the surface wetness duration requirement. The minimum wetness duration requirement (W(min)) is the number of hours required to produce 20% disease incidence or 5% disease severity on inoculated plant parts at a given temperature. The model was validated with published data from 53 controlled laboratory studies, each with at least four combinations of temperature and wetness. Validation yielded an average correlation coefficient of 0.83 and a root mean square error of 4.9 h, but there was uncertainty about the value of the input parameters for some pathogens. The value of W(min) varied from 1 to 48 h and was relatively uniform for species in the genera Cercospora, Alternaria, and Puccinia but less so for species of Phytophthora, Venturia, and Colletotrichum. Operationally, infection models may use hourly or daily weather inputs. In the case of the former, information also is required to estimate the critical dry-period interruption value, defined as the duration of a dry period at relative humidities <95% that will result in a 50% reduction in disease compared with a continuous wetness period. Pathogens were classified into three groups based on their critical dry-period interruption value. The infection model is being used to create risk maps of exotic pests for the U.S. Department of Agriculture's Animal Plant Health and Inspection Service. 相似文献
19.
Production and development of the chasmothecia of Erysiphe necator on Vitis vinifera leaves were studied using potted plants in controlled and outdoor environments and grapevines in a vineyard. The optimum temperature for ascocarp production was 20°C; fewer chasmothecia were produced at 15°C and even fewer at 25°C; at 10 and 30°C, no or very few chasmothecia were observed, and none reached maturity. Nonlinear equations describing ascocarp development as a function of time and temperature were developed, parameterized with data from experiments at constant temperatures, and evaluated under fluctuating temperatures. Goodness‐of‐fit showed high agreement between observed and predicted data: the model efficacy ranged from 0·74 to 0·97 (1·0 indicates a perfect fit), and the root mean square error ranged from 0·001 to 0·01 (zero indicates a perfect fit). The high proportion of the observed variability accounted for by these equations (R2 = 0·83–0·98) supported the hypothesis that temperature has a predominant role in ascocarp development under natural conditions, when all environmental factors interact. The equations tended to overestimate the production of mature chasmothecia (the coefficient of residual mass was ?0·23), but this inconsistency mainly occurred when rainfall apparently washed the mature chasmothecia from leaves during the logarithmic phase of the ascocarp developmental curve. Results from this work will be useful for predicting the development of chasmothecia in a vineyard and for timing the use of natural products, fungicides or biocontrol agents for reducing the population of chasmothecia, which are all more effective when they are applied to immature chasmothecia. 相似文献
20.
以草地贪夜蛾Spodoptera frugiperda为寄主,研究了不同温度下淡足侧沟茧蜂Microplitis pallidipes对草地贪夜蛾寄生和生长发育的影响,并建立了淡足侧沟茧蜂发育速率与温度的关系模型。结果表明：在试验温度范围内,淡足侧沟茧蜂均能在草地贪夜蛾幼虫体内完成发育,23℃和32℃时,淡足侧沟茧蜂对草地贪夜蛾寄生率最高（＞60%）,20℃和26℃时,淡足侧沟茧蜂结茧率最高（＞90%）。随着温度的升高,淡足侧沟茧蜂的发育历期（卵-幼虫期、蛹期和成虫期）明显缩短。Logistic曲线和线性模型均可拟合淡足侧沟茧蜂发育速率与温度的关系,但在卵-幼虫期和蛹期阶段,线性模型的拟合效果较好,成虫阶段两种模型均可;卵-幼虫、蛹和成虫的发育起始温度依次为10.2℃、15.08℃和5.43℃,有效积温依次为110.27日·度、81.10日·度和107.53日·度。 相似文献