Patterns of airborne conidia of Stemphylium vesicarium, the causal agent of brown spot disease of pears, in relation to weather conditions

Seven-day volumetric spore samplers were installed in pear orchards of northern Italy, in the years between 1993 and 2002, and operated continuously during the development of brown spot epidemics (mid-April–mid-August), caused by Stemphylium vesicarium. Aerial concentration of conidia was recorded at 2 h intervals to study their diurnal and seasonal patterns and the influence of weather conditions. The diurnal periodicity of aerial conidia showed a peak around midday and low counts in the dark. The increase in spore concentration was significantly correlated with the reduction of relative humidity and wetness in early morning, and the increase of wind in late morning and afternoon. Conidia of S. vesicarium became easily airborne to form a regular component of the air-spora in pear orchards, while ascospores were caught only sporadically. Differences between years concerned total spore counts and numbers of peaks (defined as days with more than 30 conidia/m³ air per day). Periods with highest spore counts occurred in late-May to early-June (in 2 years), mid to end of June (5 years), or after mid-July (3 years). There was a significant correlation between spore peaks and days with favourable weather conditions, defined as days with air temperature between 15 and 25°C and high humidity, particularly a wet period longer than 10 h. Occurrence of one or more consecutive days with favourable weather conditions determined an increase in the airborne concentration of conidia, which usually lasted some days and then decreased.     

The variation in spore concentrations of selected fungal taxa associated with weather conditions in Szczecin,Poland, 2004–2006

The investigation of airborne fungal spore concentrations was carried out in Szczecin, Poland between 2004 and 2006. The objective of the studies was to determine a seasonal variation in concentrations of selected fungal spore types due to meteorological parameters. The presence of spores of ten taxa: Cladosporium, Ganoderma, Alternaria, Epicoccum, Didymella, Torula, Dreschlera‐type, Polythrincium, Stemphylium and Pithomyces was recorded in Szczecin using a volumetric method (Hirst type). Fungal spores were present in the air in large numbers in summer. The highest concentrations were noted in June, July and August. The peak period was recorded in August for most of the studied spore types: Ganoderma, Alternaria, Epicoccum, Dreschlera‐type, Polythrincium and Stemphylium. Cladosporium and Didymella spores reached their highest concentrations in July while concentrations of Torula were highest in May and Pithomyces in September. Multiple regression analysis was performed for three fungal seasons: 2004, 2005, and 2006. Spore concentrations were positively correlated with minimum temperature for seven spore types in 2004, for five spore types in 2005, and for eight spore types in 2006 (significance level of α = 0.05). Some spore types are also significantly correlation among their concentrations, pressure, relative humidity and rain. Minimum temperature appeared to be the most influential factor for most spore types.     

Influence of urban climate upon distribution of airborne Deuteromycete spore concentrations in Mexico City

 The effect of an urban climate upon the spatial and temporal distribution of Deuteromycete spores was studied during 1991 using Burkard volumetric spore traps in two areas of Mexico City with different degrees of urbanization. Deuteromycete conidia formed the largest component of the total airborne fungal spore load in the atmosphere of Mexico City, contributing 52% of the spores trapped in an urban-residential area (southern area) and 65% of those in an urban-commercial area (central area). Among the most common spore types, Cladosporium and Alternaria showed a marked seasonal periodicity with significant differences in concentration (P<0.05) between the dry and wet seasons. Maximum conidial concentrations were found during the end of the wet season and the beginning of the cool, dry season (October–December). Daily mean concentrations of the predominant airborne spore types did not differ significantly between the southern and central areas. Daily mean spore concentrations were significantly correlated (P<0.05) in southern and central areas with maximum temperature (south, r = –0.35; central, r = –0.40) and relative humidity (south, r = 0.43; central, r = 0.29) from the previous day. Moreover, multiple regression analysis of spore concentrations with several meteorological factors showed significant interactions between fungal spores, relative humidity and maximum temperature in both areas. The diurnal periodicity of Cladosporium conidia characteristically showed two or three peaks in concentration during the day at 0200–0400, ∼ 1400 and 2000–2200 hours, while that of Alternaria showed only one peak (1200 to 2000 hours) in both areas. Maximum concentrations of these spores generally occurred 2–4 h earlier in the southern than in the central area. The lag in reaching maximum concentrations in the central area probably resulted from differences in the local conditions between the study areas, and from spores transported aerially into the city from distant sources. The analysis of maximum hourly concentrations of Cladosporium and Alternaria spores during 1 month of the dry season (February), and another month of the wet season (September) showed significant differences between the two study areas. Environmental factors and sources (green areas) affected diurnal changes in conidial concentration in the southern area (urbanization index, UI, 0.25), but not in the central area (UI 0.97). In general, spore concentrations were greatest in the southern area when relative humidities were low, and temperatures and wind velocities were high. It was difficult to establish effects of climatic factors on the spore concentration in the city centre. This probably results from the large amounts of air pollution, the heat island phenomenon, and from the distant origin of trapped conidia obviating aerial transport. Nevertheless, the seasonal and diurnal distributions of conidia found were similar to those reported for other tropical regions of the world. Received: 13 August 1996 / Accepted: 4 December 1996     

Artificial neural network models of relationships between <Emphasis Type="Italic">Alternaria</Emphasis> spores and meteorological factors in Szczecin (Poland)

Alternaria is an airborne fungal spore type known to trigger respiratory allergy symptoms in sensitive patients. Aiming to reduce the risk for allergic individuals, we constructed predictive models for the fungal spore circulation in Szczecin, Poland. Monthly forecasting models were developed for the airborne spore concentrations of Alternaria, which is one of the most abundant fungal taxa in the area. Aerobiological sampling was conducted over 2004–2007, using a Lanzoni trap. Simultaneously, the following meteorological parameters were recorded: daily level of precipitation; maximum and average wind speed; relative humidity; and maximum, minimum, average, and dew point temperature. The original factors as well as with lags (up to 3 days) were used as the explaining variables. Due to non-linearity and non-normality of the data set, the modelling technique applied was the artificial neural network (ANN) method. The final model was a split model with classification (spore presence or absence) followed by regression for spore seasons and log(x+1) transformed Alternaria spore concentration. All variables except maximum wind speed and precipitation were important factors in the overall classification model. In the regression model for spore seasons, close relationships were noted between Alternaria spore concentration and average and maximum temperature (on the same day and 3 days previously), humidity (with lag 1) and maximum wind speed 2 days previously. The most important variable was humidity recorded on the same day. Our study illustrates a novel approach to modelling of time series with short spore seasons, and indicates that the ANN method provides the possibility of forecasting Alternaria spore concentration with high accuracy.     

Occurrence of Didymella ascospores in western and southern Poland in 2004–2006

The concentration of airborne Didymella spores has been investigated at two monitoring sites situated along the west–south transect in Poland (Szczecin, Kraków), i.e. from a height of 100 to 219 m, respectively, above sea level. The aerobiological monitoring of fungal spores was performed by means of two Lanzoni volumetric spore traps. The high Didymella spore numbers were observed at both cities in June, July and August. Statistically significant correlations have been found mainly between the Didymella spore concentrations in the air and the minimum air temperature and relative air humidity. The spore count of Didymella is determined by the diversity of local flora and weather conditions, especially by the relative air humidity. The identification of factors that influence and shape spore concentrations may significantly improve the current methods of allergy prevention.     

Airborne <Emphasis Type="Italic">Aspergillus</Emphasis> and <Emphasis Type="Italic">Penicillium</Emphasis> in the atmosphere of Szczecin, (Poland) (2004–2009)

The investigation into airborne fungal spore concentrations was conducted in Szczecin (Poland) between 2004 and 2009. The objective of the studies was to determine a seasonal variation in concentrations of amerospores on the basis of meteorological parameters. The presence of spores in Szczecin was recorded using a volumetric method. Fungal spores were present in the air in high numbers in late summer and early autumn. The highest concentrations were noted in September, October and November. The peak period was recorded in August, September, October and November. The highest annual number of spores occurred in 2005 and 2007 and the lowest in 2006. High values of daily concentration of amerospores occurred during the afternoon and late at night. In 2005 and 2007 the late-night maximum was overdue about 1 or 2 h. For daily values of dew point temperature and relative humidity, the coefficients were positive, significant for p = 0.001 and ranged from 0.342 to 0.258. The average wind speed was positively correlated for p = 0.01 and the coefficient was 0.291. The similar relations were noted for hourly values of spore concentrations for p = 0.05, p = 0.01 and p = 0.001. For these spore types, the dew point temperature and relative humidity appeared to be the most influential factor.     

1961—2007年海口市气候环境变化及其对城市发展的响应

基于海口市1961—2007年的气象资料以及1989—2007年的城市化水平,对海口市气候环境变化及其与城市化水平的关系进行了分析.结果表明：与1961—1990年相比,海口市1995—2007年气温呈明显的增高态势,年均增温0.93 ℃;而相对湿度则明显降低,年均湿度降低了3%;海口市年均气温、年均相对湿度与城市化水平分别呈显著和极显著相关,说明城市化较好地解释了近20年来海口市气候要素的变化.海口城市的发展,不仅改变了气候环境要素,而且影响了大气环境质量,使酸雨次数增加、年均酸雨pH值降低.     

Studies on the Concentration of Ramularia beticola Conidia in the Air Above Sugar Beet fields in Denmark

Concentrations of Ramularia beticola Faut. & Lamb. conidia in the air above 3 sugar beet (Beta vulgaris L.) field were registered for a period of 41 days altogether. A significant diurnal periodicity was revealed. Two periods of 3 and 5 days, respectively, included peaks of several thousands of conidia per m³ of air. The conidial concentrations were related to temperature, relative humidity (RH) and vapour pressure of the air, and to wind speed, dew point, rainfall and hours of sunshine. A significant effect of vapour pressure was observed for 2 fields. In one field with very low conidial concentrations, vapour pressure was nearly significant. In this field only wind speed significantly influenced dispersal of conidia. In an analysis of covariance including all data, 50% of the variation was explained by field, time of day, vapour pressure and number of hours of RH above 95% in the preceding 24h.     

Secondary leaf fall of Hevea brasiliensis: meteorological and other factors affecting infection by Colletotrichum gloeosporioides

The lower leaf surface of Hevea brasiliensis was more susceptible to infection by Colletotrichum gloeosporioides than the upper. Few lesions were produced if spore drops on susceptible leaves were allowed to dry. Lesion development after 72 h was quickest at 21 ^oC, slower at 26.5 ^oC and was stopped at 32 ^oC, probably because of bacteria in the inoculation drop. On leaflets aged 7 days from bud-burst, the effective spore dose for 50% of leaflets infected (ED₅₀) after 16 h incubation, was 260 spores and after 46 h, 120 spores/infection droplet; the minimum ED₅₀ for the upper leaf surface was about 4 spores/mm². Leaflets 15 days old, which are normally resistant, were rendered susceptible by abrading the surface with carborundum powder. Spores caught in a Hirst spore trap reached a daily maximum at 23 h, at rates of up to 440 spores/m³ air/h, but fell to low concentrations as the humidity dropped during the daytime, and also during rain. There was some correlation between disease severity and duration of 97–100% relative humidity, and moderate to severe defoliation of clone PB 86 occurred when this reached 13.5 h/day. Rainfall increases infection by prolonging the period of atmospheric saturation and leaf wetness.     

Selected airborne allergenic fungal spores and meteorological factors in Szczecin,Poland, 2004–2006

Airborne fungal spore concentrations in Szczecin, Poland, were studied between 2004 and 2006 with the objective of determining a seasonal variation in the concentrations of selected fungal spore types in relation to meteorological parameters. The presence of spores of five taxa, namely, Cladosporium, Ganoderma, Alternaria, Leptosphaeria and Didymella, was recorded using a volumetric method (Hirst type). Fungal spores were present in the air in large numbers during the summer, with the highest concentrations recorded mainly in June, July and August. The peak concentrations of two of the studied spore types, Ganoderma and Alternaria, occurred in August, while the concentrations of Cladosporium, Leptosphaeria and Didymella spores were the highest in July. Multiple regression analysis was performed for three fungal seasons—2004, 2005 and 2006. Spore concentration was found to be positively correlated with the minimum temperature. For some spore types, there was also a significant correlation between concentrations, relative humidity and rain.     

Fusarium andDidymella-neglected spores in the air

Summary This paper reports about the occurence ofFusarium- andDidymella spores in the air of Essen/FRG. During the spore season 1990, the spore concentration was measured on several days with a volumetric pollen trap by hourly analysis. The calculated amount of spores per hour is compared to the data of a pluviometer and the values of the relative humidity during the same period.The occurence of both spore types in the air and high relative humidity (>80%) are correlated in a highly significant way (P<0.001). The dispersion of spores starts when rain begins or directly after the precipitation.Didymella reaches higher concentrations thanFusarium in the air (Maximum values:Didymella 30000 spores/m³,Fusarium only 800 spores/m³). During the emission of the spores the temperature varied between 10°C und 20°C degrees. Didymella andFusarium must be an important allergenic source in the outdoor area, because of their allergen-loaded biological aerosols. The question of providing well defined extracts ofDidymella exitialis is given to the pharmaceutical industry.     

Hourly predictive artificial neural network and multivariate regression tree models of <Emphasis Type="Italic">Alternaria</Emphasis> and <Emphasis Type="Italic">Cladosporium</Emphasis> spore concentrations in Szczecin (Poland)

A study was made of the link between time of day, weather variables and the hourly content of certain fungal spores in the atmosphere of the city of Szczecin, Poland, in 2004–2007. Sampling was carried out with a Lanzoni 7-day-recording spore trap. The spores analysed belonged to the taxa Alternaria and Cladosporium. These spores were selected both for their allergenic capacity and for their high level presence in the atmosphere, particularly during summer. Spearman correlation coefficients between spore concentrations, meteorological parameters and time of day showed different indices depending on the taxon being analysed. Relative humidity (RH), air temperature, air pressure and clouds most strongly and significantly influenced the concentration of Alternaria spores. Cladosporium spores correlated less strongly and significantly than Alternaria. Multivariate regression tree analysis revealed that, at air pressures lower than 1,011 hPa the concentration of Alternaria spores was low. Under higher air pressure spore concentrations were higher, particularly when RH was lower than 36.5%. In the case of Cladosporium, under higher air pressure (>1,008 hPa), the spores analysed were more abundant, particularly after 0330 hours. In artificial neural networks, RH, air pressure and air temperature were the most important variables in the model for Alternaria spore concentration. For Cladosporium, clouds, time of day, air pressure, wind speed and dew point temperature were highly significant factors influencing spore concentration. The maximum abundance of Cladosporium spores in air fell between 1200 and 1700 hours.     

Studies on the epidemiology of Alternaria brassicicola in Brassica oleracea seed production crops

Alternaria brassicicola lesions present on overwintered leaf litter of Brassica oleracea seed production crops produced high concentrations of spores in the spring, these were able to initiate new infections on foliage and subsequently on inflorescences and pods. A vertical disease gradient developed in maturing crops, the lowest pods becoming infected first and infection spreading slowly upwards. Spores were produced abundantly after 20 h leaf wetness at a mean temperature of 13°C or more. Their release was stimulated by a fall in relative humidity but inhibited at a constant high relative humidity resulting in a daily cycle in air spore concentrations with minimum numbers occurring in the early morning and maximum numbers in the early afternoon. For most of the growing season spore movement was restricted to within the crop, however, massive release of spores and subsequent distribution over a wide area occurred when the crop was cut and later threshed. Using semi-selective agar traps spores released at these times were detected up to 1800 m downwind of the parent crop and were instrumental in infecting nearby young crops destined for seed production in the following season.     

Some components of the air spora in Jamaica and their possible medical application

A knowledge of the pollen and fungal spores which comprise the air spora is useful as a preliminary approach to the problem of respiratory allergy. Therefore, this study of the qualitative and quantitative aspects of the air spora was done. Fungal spores were found to be numerically dominant, comprising 97.73% whilst pollen comprised 0.40% of the total material observed. A small number of types made up the majority of the fungal air spora, namely, Cladosporium, the Sporobolomycetaceae group, Diatrype, Glomerella, hyaline and coloured basidiospores, and septate fusiform spores. Seasonal periodicity studies on twenty-five fungal types showed that a high number of spores were trapped for sixteen during wet months, four during cooler months, and that five showed no seasonal trends. Mean diurnal periodicity studies for the year on the same twenty-five spore types showed that all had a maximum number of spores trapped at some time during the day. Investigation of the effect of rainfall on the numbers of spores released showed that the amount and duration of rainfall, the time of day rain occurs, and the length of the dry period preceding rain were of varying importance to particular spore types.     

Powdery mildew of tobacco (Erysiphe cichoracearum DC.): Some effects of methods of inoculation and air humidity on germination of conidia and growth of hyphae on leaves*

Germination of conidia of Erysiphe cichoracearum and hyphal growth in 3 days at 23° C. and 6 mb. saturation deficit was similar, whether conidia were applied dry or suspended for up to 1 hr. in glass-distilled water before being sprayed on tobacco leaves. Growth of single conidial colonies whose hyphae were more than 333 μ long, was positively correlated with numbers per cm.² of leaf (P < 0.01) on three of the eleven times tested, mostly when conidia were sparsely distributed; ten of the regressions were positive. A greater percentage of conidia germinated at 0–1.7 mb. saturation deficit than at 7–9 mb. Subsequent growth of hyphae was greater in the drier air.     

OBSERVATIONS ON NOCTULE BATS (NYCTALUS NOCTULA) CAPTURED WHILE FEEDING

In the summer and early autumn of 1960, 1961 and 1962, noctule bats flying low, taking house crickets as these flew from a municipal rubbish tip, were captured in mist nets, ringed, released and in many cases recaptured a number of times. The flying bats showed no fear of human beings or predatory birds and did not learn to avoid the net. In June and July of each year the majority of bats caught were adult females, the flying young of the year first appearing in August though some did not fly until September and October. Young males did not reach sexual maturity in the year of their birth, though five out of fourteen females recaptured at a year old did. There was a considerable movement of adult males in the late summer, adult bats being captured in approximately equal numbers of both sexes during August and September. In October the females seemed to disappear, the majority of the bats caught during that month being males: by November the crickets had ceased to fly and no more bats could be captured though a few wero still flying on warm nights. There was a marked difference in feeding behaviour over these three years, the bats concentrating more on crickets in 1960 than in 1961 and 1962. Though the differences are not statistically significant there were indications of an increase in body weight between July and October in the years when less cricket feeding was occurring. About 50 per cent of the females captured in each of the years 1960 and 1961 were recaptured feeding on the same site in the following year: the recovery rate of males was about 30 per cent in 1961, 60 per cent in 1962.     

Dispersal of conidia of Dothidella ulei from Hevea brasiliensis

South American leaf blight caused by Dothidella ulei occurs only in tropical America, on both indigenous and cultivated Hevea spp. The conidium (Fusicladium macrosporum) is a 1-septate, dry, air-borne spore about 40 × 7 μ, occurring on the abaxial surface of dry leaves in dense, powdery, olive-green masses, and with one or both cells collapsed. The conidia adhere to the surface of water droplets, becoming turgid, and are disseminated in splash droplets. A Hirst volumetric trap, placed within a prepared source in north-west Trinidad, showed a diurnal periodicity of conidial production, with a maximum at 10.00 h and minima at night or in the early morning. On rainless days there was also a minor peak at 20.00 h. Transient increases occurred after rain, most of which fell around noon. On wet days almost equal numbers of conidia were dispersed between 10.00 and 12.00 h. Large increases occurred in 87% of all rain showers between 09.00 and 13.00 h. After 13.00 h fewer rain showers caused such increases; the lowest (36%) was between 21.00 and 01.00 h. Twice as many were trapped on sunny days (> 9 h sun) at 09.00 h when there was full sunshine, compared with overcast days (< 5 h sun). A more clearly defined morning maximum occurred on relatively windy days, compared with calmer ones. Conidial sporulation became very low, or ceased, where rain fell below a mean of 3–4 mm per day for at least 20 days. Abundant sporulation occurred with a daily rainfall about twice this amount. The results support the belief that if Dothidella ulei appeared in Malaysia its spread would be rapid and its effects damaging.     

Intradiurnal periodicity of fungal spore concentrations (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) in Cracow, Poland

Aerobiological monitoring enables the definition of seasonal fungal spore concentrations and also intradiurnal time when the highest concentrations of spores could cause or increase allergy symptoms. These data are useful to estimate symptoms of disease, duration of infection and how advanced the illness is in people suffering from fungal allergens. The aim of the study was to compare the concentrations of fungal spores (Alternaria, Botrytis, Cladosporium, Didymella, Ganoderma) during dry and rainy periods and to analyse their intradiurnal changes. Average daily spore concentrations in dry and rainy periods were compared, using z test, separately for each taxon, season and for a combined 3-year period. Intradiurnal periodicity of fungal spore concentrations was analysed on the basis of three complementary diagrams. These spore concentrations were presented using three curves for all, dry and rainy days in 1997–1999 (April–November). The spore percentage in particular hours was normalized in relation to the daily spore sum accepted as 100%. Two further diagrams enabled the more precise analysis of the highest concentrations in dry days. Daily Botrytis and Cladosporium spore concentrations did not show significant differences between dry and rainy periods. In the case of Didymella and Ganoderma spore concentrations, there were no significant differences between both weather types in the single years, although there was a significant difference when a 3-year period was considered. The differences between daily concentrations of Alternaria spores in dry and rainy periods occurred in 1997 and in a 3-year period. Intradiurnal periodicity of spore concentrations was different for ‘dry’ and ‘wet’ fungal spores. Dry spores are released from the spore-producing parts of the fungus under conditions of decreasing humidity and increasing airflow. Examples of dry spores are those from Alternaria, Cladosporium and Botrytis. Wet spores, such as those from many Ascomycetes (Didymella) and Basidiomycetes (Ganoderma), are released into the atmosphere by processes related to humidity conditions or rain. The highest concentrations of ‘dry’ spores were observed early in the afternoon, while highest values of ‘wet’ spore concentrations occurred in the predawn hours. Statistically non-significant differences between daily spore concentrations in dry and rainy periods of single seasons were found except for Alternaria. Statistically significant differences could occur when the studied period was longer than one season (Alternaria, Didymella, Ganoderma). The highest concentrations of Alternaria, Botrytis and Cladosporium spores were recorded at noon and early in the afternoon. Concentrations of Didymella and Ganoderma spores were highest in the predawn hours.     

The aerobiology of the ascospores

Atmospheric ascospores have been monitored using volumetric spore trap. Spore concentration data were analysed using Spearman's correlation. Our results show that the meteorological factor with the greatest effect on spore concentration was the duration of rain. Temperature increase strongly reduced the ascospore concentration; but the length of windless periods resulted in an increase in spore count. The only measurable effect wind perse actually had on spore count, was registered when a strong wind blew after a long windless period. We observed that the count of ascospores during wet weather could surpass the total concentration of dry conidia measured on a typical, highly polluted summer day. Using selected air samples to study the effect of storms, certain aspects of long-distance spore transport were elucidated. We describe here three main strategies for long-range ascospore transport, "splash-off", "secondary emission" and "sporematrix projectiles".     

Pollen analysis of honey from the Baltic region,Estonia

The effect of varying weather conditions on the hourly number of airborne Cladosporium conidia was studied in forest environments during three summers. All factors having diurnal periodicity correlated significantly with the number of spores. Because of the great variation in weather and the interaction of weather factors, the most important factors were not the same for each summer. Temperature was important in each year. Relative humidity was most important in the first rainy summer, and precipitation was more important during the two drier summers than in the first summer. The maximum spore counts were obtained at the onset of rain, indicating the effectiveness of the first rain drops in detaching conidia. The amount of water precipitated also promoted the production of conidia, since it correlated positively with the number of spores in the air several hours later. Spore detachment also seemed to be closely related to decreases in relative humidity and increases in wind velocity which occurred in the morning. An increase in wind velocity from 0.5–1.0 m^?s increased the number of spores most effectively.