Quantitative relationships between infection by the hop downy mildew pathogen, Pseudoperonospora hutnuli, and weather and inoculum factors

Experiments are described in which successive groups of healthy, susceptible, potted hop-plants were exposed, each 24 h, to the weather and to sources of Pseudoperonospora kumuli inoculum in an unsprayed hop garden for 48 h periods during May and June in 1969, 1970 and 1971. The infection which arose after standardized incubation in isolation was measured and then related, both by inspection and by multiple regression analysis, to the conditions during exposure. Severe infection could be associated with certain sequences of events in which rain contributed substantially to plant wetness; relatively light or no infection developed when dew provided the wetness of a period. Infection was markedly correlated with the occurrence of infection periods, as defined from earlier growth-room studies, especially when dew-wetness was omitted. The regression analysis showed that, in all years, infection was highly correlated with variables reflecting wet conditions. It was inconsistently correlated with vapour pressure deficit (VPD) and with sunshine, not at all with temperature, and with airborne spore concentration only in the combined years. The spore catches of a funnel trap, used in 1971, which depended upon rain varied closely with infection. R² values for multiple regression equations indicated that, in the years separately and together, well over 70% of the variation in infection could be explained by the environmental variables and, in 1971, almost 90%. Variables (temperature, VPD, airborne spores) which singly were poorly correlated with infection often significantly improved regression equations which were based on variables expressing wetness. When prediction of each year's infection levels was attempted using selected regression equations calculated from data of the other 2 years there was, in general, very good agreement between measured and estimated values. The best predictions were given by an equation utilizing rain-wetness duration, rainfall amount and airborne spore concentration while an equation based solely on relative humidity and rainfall was only slightly inferior. The results are discussed in relation to the possible value of the regression models for short-term forecasting of hop downy mildew.     

Effects of temperature and rainfall on the incidence of wilt (Verticillium albo-atrum) in hops

Wilt incidence in certain hop cultivars recorded during 15 years of experiments on a plot infested with a virulent strain of V. albo-atrum, and over shorter periods on various infested farm sites, was studied by multiple regression analysis in relation to rainfall and soil temperature at various periods during the growing season. In the least-resistant cultivar, Fuggle, the incidence of wilt was always high, and was independent of rainfall and soil temperature. Wilt incidence in other cultivars showed a negative correlation with mean soil temperature at 20 cm for the period mid-April to late June; no other single or multiple regression was consistently significant. It was concluded that the commonly observed association of high wilt incidence with wet weather in early summer is attributable to low soil temperature rather than to high rainfall.     

Pollen grain viability in Parietaria judaica L. during the long blooming period and correlation with meteorological conditions and allergic diseases

Abstract

Pollen grain viability and starch presence in pollen were followed during the long blooming period (May-November) of Parietaria judaica, the most widespread pellitory in Italy, responsible for many cases of allergic diseases. Observations were carried out near Siena (Tuscany), in the years 1978 and 1979.

Viability is high in late spring and early autumn, and pollen grains are starchy. The presence of starchless grains is always related to low viability: a production of pollen with a low viability occurs at the beginning and end of blooming, and also in summer, during drought periods. Pollen grain viability varies widely during the blooming period, and its variations are correlated to meteorological conditions, mainly rainfall and temperature.

Allergic diseases due to pellitory, however, are mainly reported between April and July, and on the other hand a small amount of patients states that they suffer all the year round. The discrepancies between the periods of viable pollen production and of declared symptoms by patients, are discussed.     

Relationship between meteorological conditions and natural reproduction behavior of the four famous Chinese carps

Known as the four famous carps in China, black carp (Mylopharyngodon piceus), grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) are commercially important fish species with a high production in China. To reveal the relationships between meteorological conditions and the natural spawning behavior of these fishes, we considered six meteorological factors (including wind, rainfall, temperature, air pressure, sunshine hours and humidity) and the weather conditions in 80 spawning events. The results showed that the spawning activities were more likely to be activated in consecutive rainy days or days when weather changed drastically, while the spawning activities showed no tendency for the weather type except consecutive rainy days. Our analyses also showed that the average rainfall in the initial spawning days is higher than that in the spawning time windows (the time from the earliest spawning activity to the latest spawning activity), while other meteorological elements remained at more or less the same values in both time periods; spawning activity tended to happen in days when the average air pressure was going down or the average temperature going up, while the other meteorological elements showed no consistent tendency.     

Factors affecting migration patterns of juvenile river herring in a coastal Massachusetts stream

Juvenile anadromous river herring (alewives, Alosa pseudoharengus, and blueback herring, Alosa aestivalis) spend 3–7 months in freshwater before migrating to the ocean, often exhibiting waves of early and late migrations. Migratory patterns and associated abiotic and biotic factors were examined for both species migrating in 2003 from Herring River in Bourne Massachusetts. Migrating herring were grouped into two temporal periods and separated by species. Relationships between abiotic (water temperature, lunar phase, and precipitation) and biotic (size, age, growth rate, and hatch date) factors and the timing of out-migration (transition to seawater) were examined. Blueback herring migration coincided with a sharp decrease in temperature consistent with the time of year. Peaks in alewive migration may reflect adaptive traits maximizing likelihood of survival through seasonal marginal stream habitats and also avoiding lethal water temperatures in winter. Migrating bluebacks exhibited a single migratory period (late September–October) which occurred between the early and late migratory pulses of the alewives. These patterns may also represent distinct migration strategies between early and late migrating alewives and between the two species of river herring. Early migration may be a mechanism by which factors such as competition and low food availability are mitigated. In contrast, environmental conditions during the post hatching time of late migrators may allow for a size maximizing strategy that promotes migration from the nursery area as late as possible.     

The breeding season of tilapia, Oreochromis niloticus L. in Lake Awassa (Ethiopian rift valley)

The breeding season of Oreochromis niloticus in Lake Awassa was studied from fish caught monthly from December 1987 to November 1988 in relation to a number of environmental factors. Fish at various stages of gonad development and spawning were caught in almost all months, but breeding fish were more frequent twice a year: main peak occurred during January–March and a secondary one occurred during July–September. Gonadosomatic index (GSI) values peaked twice in the study year, a major peak being during January–March and a less pronounced one during July–September. Thus, it was concluded that O. niloticus in Lake Awassa breeds intensively in the former and less intensively during the latter period, and that some breeding occurs at any time of the year. Intensive breeding activity during January–March appeared associated with increase in solar radiation and sunshine hours d^–1 whereas that during July–September appeared associated with heavy rainfall. However, intensive breeding in both periods coincided with increase in phytoplankton biomass. Previously, phytoplankton biomass in this lake is shown to increase following increase in nutrients due to mixing- and rainfall-associated changes in the hydrography and hydrology of the lake. Thus, although further studies are required, increase in phytoplankton may be one of the environmental cues to stimulate spawning in O. niloticus in Lake Awassa whereas other factors such as sunshine and rainfall may have indirect roles through their effects on the hydrology and hydrography of the lake ultimately resulting in changes in phytoplankton biomass.     

On the sunny side of (new) life: Effect of sunshine duration on age at first reproduction in Japanese macaques (Macaca fuscata)

To produce offspring early in life is energetically demanding and depends greatly on environmental conditions. In female primates, age at first reproduction (AFR) has been associated with social parameters (e.g., population density and social rank), food availability and meteorological conditions (e.g., photoperiod, rainfall patterns, and temperature). Regarding the latter, less attention has been given to the influence of sunshine. In nonhuman primates, including the northern‐most distributed Japanese macaque (Macaca fuscata), sunbathing is an effective thermoregulatory strategy to maintain sufficient energy intake during harsh winter months. Furthermore, the energetic value of sunshine and its role in the synthesis of essential vitamins important for sexual development and overall fertility is well investigated using human and animal models. In the present study, we hypothesized that female's AFR is influenced by the amount of sunshine in a semi‐free‐ranging, provisioned a group of Japanese macaques. To test this, we gathered data on sunshine duration in the year females theoretically experienced the onset of puberty. This phase of the female life cycle is particularly prone to the effects of environmental conditions. In addition to the investigation of sunshine duration and other meteorological conditions (i.e., rainfall and temperature) we controlled for social parameters (i.e., group size and sex ratio) as potential covariates. We found a clear effect of sunshine duration on female AFR: Females who entered puberty in years with more sunshine reproduced for the first time at significantly younger ages than females who experienced less sunshine during this specific period of their development. Possible mechanisms for how the sunshine influences sexual maturation in Japanese macaques are discussed.     

Seasonal fluctuations,spatial distribution and natural enemies of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Psyllidae) in Iran

Population dynamics of the Asian citrus psyllid Diaphorina citri Kuwayama was studied in two‐week intervals throughout the season on lemon in a citrus orchard in Southern Baluchistan, Iran. Population peaks were observed in March, April and September 2007 to January 2008. Population levels were positively related to the availability of new shoot flushes, which were in turn related to the weekly minimum temperature. Also, the nymph population peaks were observed in three periods (beginning of March, end of August and end of January). Results indicated that moderate climatic conditions coupled with the flushing of citrus trees are two main factors for an increase of the development and activity of nymphs resulting in pest population increase, while extremes of both high and low temperatures, low relative humidity and high rainfall were detrimental. Four coccinellids (Coleoptera: Coccinellidae), one syrphid (Diptera: Syrphidae), two parasitoids (Hymenoptera) and two spiders (Araneae) were determined as natural enemies of the psyllid in the studied area.     

Seasonal variation of thermoregulatory behaviour in the Hippopotamus (Hippopotamus amphibius)

The hippopotamus (Hippopotamus amphibius) spends more than 12 h a day in the water. Hippos are often submitted to water temperatures that vary with the seasons. We hypothesize that this difference between cool and warm water temperatures leads to variations in behavioural thermoregulation. We recorded the exposure of hippos to sunshine at the beginning and at the end of the dry season. Our results show that (1) sunshine exposure lasted much longer in cool water and (2) sun-bathing occurred during the hottest hours. It is therefore likely that in cool water hippos were cold and expressed an original behaviour of search for heat.     

丹参品质与主导气候因子的灰色关联度分析

气候因子对丹参(Salvia miltiorrhiza Bunge)生长及有效成分含量有重要影响,为科学选择人工种植基地,需要明确影响丹参品质的主导气候因子。研究了丹参在商洛6个不同地区的生长量及有效成分含量差异,并应用灰色关联度分析了其与气候因子的关系,结果表明:6地区丹参有效成分含量均达到药典要求,但品质存在显著差异。年日照和年均降水量是影响丹参根系生长量的主导因子;无霜期与年极高温度是影响丹参素含量的主导因子;7月份均温、年均温度、年极高温度是影响丹参酮IIA含量的主导因子;年日照、无霜期是影响丹酚酸B含量的主导因子。以上几个指标可以作为选择丹参适生基地的参考指标,为科学合理的选择丹参规范化种植基地,保证中成药生产原料质量提供参考。     

Influence of Air Temperature on the Release of Ascospores of Venturia inaequalis

Abstract The influence of air temperature on the release pattern of Venturia inaequalis ascospores was studied by volumetric spore samplers in two spore sampling periods. In the first period (1991–1996; Passo Segni, Ferrara), 15 ascospore dispersal events were considered occurring in daylight, with high spore counts (168–5892 ascospores per m³ air per event), at an average temperature between 8.4 and 20.3°C. Both the length of the ascospore release period and distribution of airborne spores over time were significantly influenced by temperature. A logistic regression model was used to fit the proportion of ascospores trapped from the orchard air as a function of time after the beginning of the discharge event and air temperature. The accuracy of this equation was tested against data collected in the second spore sampling period (1997–2000; Sala Bolognese, Bologna, and Castelfranco, Modena); 16 dispersal events were considered, triggered by rainfall that occurred both in the dark and in daylight, with low to high spore counts (29–458 ascospores per m³ air per event), at an average temperature between 2.8 and 14.3°C. There was a general agreement between the proportion of ascospores trapped from the orchard air during these events and that estimated by using the logistic equation – in most cases, actual and estimated values showed a high coincidence. Statistical comparison showed a significant correlation (r=0.93, P < 0.01) between observed and estimated data.     

Day-to-day variation in nitrogenase activity of Alnus incana explained by weather variables: a multivariate time series analysis

A modelling system is described that indicates the extent to which day-to-day variations in nitrogenase activity in young Alnus incana (L.) Moench, grown in defined conditions in the field, may be affected by weather conditions both during and prior to the day of measurement. Nitrogenase activity (acetylene reduction activity, ARA) was measured weekly on intact field-grown grey alder (A. incana) plants, 0.15–0.42 m tall at planting, nodulated with Frankia. The measurements were done at noon on two groups of plants in 1987 and on two other groups in 1988. Each group was made up of five or six plants. Seven weather variables: daily sunshine hours, daily mean, maximum and minimum air temperature, daily mean and 1300 h relative humidity, and daily rainfall were used. The relation between log(ARA/leaf area) and the weather variables were analysed using a PLS model (partial least squares projection to latent structures). The advantage of PLS is that it can handle x-variables that are correlated. Data from 1987 were chosen as a training set. Multivariate PLS time series analysis was made by adding, in a stepwise manner, the weather data up to 5 d before the day of measurement. This procedure gave six models with n * 7 x-variables (n= 1–6). With the models from the time series analysis of 1987 data, true predictions of ARA per leaf area were made from weather data 1988 (test set 1) and from ‘early-season’ weather data from 1987 and 1988 (test set 2). The variation in ARA/leaf area could be predicted from the weather conditions. The predictions of the two test sets improved when the weather conditions one and two days before the day of measurements were added to the model. The further addition of weather data from 3 to 5 d before the day of measurement did not improve the model. The good predictions of ARA/leaf area show that the alders responded to the variable weather conditions in the same way in 1988 as in 1987, despite the ten-fold difference in size (leaf area) at the end of the growing season. Among the weather variables, air temperature and the daily sunshine hours were positively correlated to ARA, while relative air humidity and rainfall were negatively correlated to ARA. The daily minimum temperature and rainfall appeared to have least impact on ARA. By use of PLS, we could extract information out of a data set containing highly correlated x-variables, information that is non-accessible with conventional statistical tools such as multiple regression. When making measurements of nitrogenase activities under field conditions, we propose that attention should be paid to the weather conditions on the days preceding the day of measurement. The day-to-day variation in nitrogenase activity is discussed with reference to known effects of stress factors under controlled conditions.     

Identifying environmental factors impacting yellow mosaic virus disease of green gram (Vigna radiata L.) Wilczek

The relationship between environmental factors and the incidence of yellow mosaic virus disease in green gram was studied for the period of 23?years using historical data on disease index (DI) and environmental factors from 1985 to 2007. The environmental factors showed consistently significant correlations with DI during the 29th–33rd standard meteorological week (SMW) periods and the same period was taken for further analysis. Among the environmental factors, maximum temperature was highly positively correlated (r?=?0.63), followed by sunshine hours in SMW 29 (r?=?0.48), with the disease. However, rainfall during SMW 30–33 (r?=??0.38) and evening relative humidity during SMW 29–33 (r?=??0.42) were negatively correlated with disease. As these four environmental factors contribute mainly to disease, same were used to develop the functional models by conducting multiple regression analysis for the period SMW 29–33. Among these, linear model gave highest R² value (0.47) and this model was validated for the periods 2008–2010 and the predicted estimates were in full agreement with the observed estimates (R²?=?0.874).     

The effects of rainfall and shade on the occurrence of three mite pests of tea in Ceylon

Outbreaks of the red spider mite (Oligonychus coffeae Nietn.), the purple mite (Calacarus carinatus Green) and the scarlet mite (Brevipalpus californicus Banks) of tea were closely associated with the monthly rainfall pattern. Peak numbers occurred during the intermonsoonal dry periods. The relationship between mite numbers and the rainfall pattern suggests that control measures should commence at the end of the first month after the dry season begins. More red spider mites, but fewer purple mites, occurred on tea grown under shaded conditions. Observations on the relationship between scarlet mite numbers and shade were inconclusive. It is suggested that, in addition to direct effects of rainfall and shade, mite numbers are determined by certain biochemical processes that take place within the tea leaves.     

西安4种落叶乔木物候期对气候变化的响应

以西安1979—2018年的气候资料和植物物候观测资料为基础,采用分段回归和趋势倾向率等方法,分析了毛白杨(Populus tomentosa)、杜梨(Pyrus betulifolia)、七叶树(Aesculus chinensis)和灯台树(Bothrocaryum controversum)4种落叶乔木展叶盛期和叶全变色期的生长趋势,使用偏相关分析探讨了气温、降水和日照时数与物候期的关系并通过偏最小二乘回归(Partial Least Squares, PLS)判断气候变量对物候期的综合影响。结果表明：(1)1979—2018年,4种乔木的生长季长度延长,整体表现为春季物候期提前,秋季物候期推迟;(2)展叶盛期物候指标与叶全变色期物候指标,转折均发生在1982年;转折后,物候特征变化显著,春季物候的提前速率和秋季物候的推迟速率加快,展叶盛期平均提前3.8d/10a,叶全变色期平均推迟4.7d/10a;(3)展叶盛期与春季气温表现为极显著负相关,叶变色期与秋季气温表现为显著正相关;降水对植物物候的影响不显著;春季物候与日照时数呈现极显著负相关关系,秋季物候期与日照时数呈不显著正相关...     

Forecasting migration of cereal aphids (Hemiptera: Aphididae) in autumn and spring

The migration of cereal aphids and the time of their arrival on winter cereal crops in autumn and spring are of particular importance for plant disease (e.g. barley yellow dwarf virus infection) and related yield losses. In order to identify days with migration potentials in autumn and spring, suction trap data from 29 and 45 case studies (locations and years), respectively, were set‐off against meteorological parameters, focusing on the early immigration periods in autumn (22 September to 1 November) and spring (1 May to 9 June). The number of cereal aphids caught in a suction trap increased with increasing temperature, global radiation and duration of sunshine and decreased with increasing precipitation, relative humidity and wind speed. According to linear regression analyses, the temperature, global radiation and wind speed were most frequently and significantly associated with migration, suggesting that they have a major impact on flight activity. For subsequent model development, suction trap catches from different case studies were pooled and binarily classified as days with or without migration as defined by a certain number of migrating cereal aphids. Linear discriminant analyses of several predictor variables (assessed during light hours of a given day) were then performed based on the binary response variables. Three models were used to predict days with suction trap catches ≥1, ≥4 or ≥10 migrating cereal aphids in autumn. Due to the predominance of Rhopalosiphum padi individuals (99.3% of total cereal aphid catch), no distinction between species (R. padi and Sitobion avenae) was made in autumn. As the suction trap catches were lower and species dominance changed in spring, three further models were developed for analysis of all cereal aphid species, R. padi only, and Metopolophium dirhodum and S. avenae combined in spring. The empirical, cross‐classification and receiver operating characteristic analyses performed for model validation showed different levels of prediction accuracy. Additional datasets selected at random before model construction and parameterization showed that predictions by the six migration models were 33–81% correct. The models are useful for determining when to start field evaluations. Furthermore, they provide information on the size of the migrating aphid population and, thus, on the importance of immigration for early aphid population development in cereal crops in a given season.     

Zur Rolle des Pektins bei der Ausprägung sorten- und jahresbedingter Unterschiede der Naßfäuleanfälligkeit von Kartoffelknollen

The influence of soil moisture and mean day temperature of July to September on pectin structure and soft rot resistance of potato tubers was investigated. Tuber samples of middle early and middle late potato cultivars respectively were tested from 1976 to 1979. Cultivar characteristics as well as growth conditions effect the pectin structure. The tuber tissue of soft rot resistant cultivars contains relative high amounts of esterified pectin. The pectin esterification was promoted by drought during vegetation periods (1976, 1978). A late rise of metabolic activity caused by rainfall at the end of the vegetation period (1978) increased the amount of soluble pectin in the cell wall. This lack of pectin stabilization facilitates tissue maceration by soft rot bacteria. Increased pectin solubility was also caused by unfavorable storing conditions of potato tubers. A low degree of esterification and high solubility of the cell wall pectin affect the relative resistance of potato tubers against soft rot caused by Erwinia carotovora var. atro-septica (van Hall) Dye adversely.     

Grasshopper population dynamics and meteorological parameters - lessons from a case study

Population dynamics of grasshoppers differing in phenology were analysed on a xerothermic meadow in central Germany, The study was based on standardized annual sweep net samples in relation to meteorological factors |mean and maximum temperature, rainfall, sunshine) from May through September of current and previous year, respectively. Three grasshopper species, the early hatching Euthystira brachyptera , the phenologically intervening Stenohothrtis lineatus. and the late hatching Gomphocerus rufus ., were investigated over ten years during three periods: 1971 74, 1983 85, 198789. By means of stepwise linear regression and a cross-validation procedure a subset of meteorological parameters was extracted which best described the field sampling data of the grasshoppers. This subset of variables was then used in multiple linear regression analyses in order to model the long-term population dynamics of the grasshoppers from 1971 to 1990, The selected variables for each species revealed different influences of meteorological parameter combinations reflecting the different phenologies. The dynamics of the three gomphocerine species modelled for 20 yr (1971 1990) differed both with maxima and minima in different years and in the fluctuation factors from 29 (E. brachyptera) to 155 (S. lineatus). In comparison with fluctuation trends in populations of other sites within the region some species-specific and habitat-specific population dynamics must be assumed. There were no significant correlations between annual aridity (precipitation-temperature)-indices and densities of the three populations studied.     

Migration of the Nathusius’ pipistrelle<Emphasis Type="Italic">Pipistrellus nathusii</Emphasis> (Vespertilionidae) along the Vistula Split

Migration ofPipistrellus nathusii (Keyserling and Blasius, 1839) was studied from 1995 to 1998 at the Vistula Split, northern Poland. The direction of bat movements during the night were distinguished by two ultrasound detectors facing in opposite directions and connected into a stereo system. To obtain information about fluctuations in the relative density of bats in the study area, bird nest boxes and bat boxes were checked as well. A combination of the results of these two methods allowed the identification of seasonal movements. Spring migration started at the beginning of May and continued until the end of the month. Autumn migration started in mid-July and lasted until mid-September. The peaks in spring and late summer migrations resulted from longer migration activity during nights.     

Incidence of fungal species associated with leaf rot disease of coconut palms in relation to weather and the stage of lesion development

Leaf rot disease (LRD) of coconut occurs in Kerala State, India, and is generally severe during the monsoon, a time of high rainfall and r.h. and low maximum temperature. The pathogenic fungi Colletotrichum gloeosporioides, Exserohilum rostratum, Gliocladium vermoeseni, Fusarium solani, F. moniliforme var. intermedium, Thielaviopsis paradoxa and Rhizoctonia solani were among 14 species isolated from spindles of palms with LRD in multiple samplings of two experiments, each lasting 1 year. Co-occurrence of fungi was observed in 70–76% of spindles although leaf pieces yielded mostly individual fungi irrespective of the stage of lesion development. C. gloeosporioides occurred most frequently on early lesions. The incidence of C. gloeosporioides was most strongly correlated with rainfall and r.h. and, negatively, with maximum temperature and hours of sunshine. It was the fungus isolated most commonly during the monsoon and occurred on early lesions more frequently than on advanced lesions (determined in one experiment). C. gloeosporioides is thus implicated as the principal pathogen involved in initiation of the disease during monsoons. Its relatively low incidence in the dry season suggests a quiescent phase between periods of parasitic activity. E. rostratum was isolated less frequently and its incidence was less strongly or consistently correlated with weather or with the stage of lesion development. Fusarium spp. and R. solani were associated with dryer weather and higher temperatures. The Fusarium spp. were the fungi isolated most commonly during part of the dry season (January-March) and occurred more on early than on advanced lesions at one sample (January) when they may have been primary disease agents. R. solani was also more frequent on advanced lesions and may be principally a secondary coloniser of established lesions. The incidence of other fungi, which occurred less frequently and more sporadically, was not associated with weather or consistently with different stages of lesion development.