Automatic Volumetric Spore Trap Research Articles

Volumetric Spore Traps Are a Viable Alternative Tool for Estimating Heterobasidion Infection Risk

Prophylactic stump treatments against the conifer root rot fungus Heterobasidion annosum s.l. should take into account the airborne inoculum density of the pathogen, in order to be economically feasible. Our objective was to test if an automatic volumetric spore trap (AVST) could be used as a sensitive alternative of passive traps for quantifying Heterobasidion airspora in forest stands. The routinely used wood disc exposure method (WDE) was implemented simultaneously with AVST in five coniferous monocultures and three near-natural stands without silvicultural management in Czechia. Air sampling took place for 24-h intervals in five months of the main sporulation period. The atmospheric concentration of H. annosum s.l. spores (cHa) was determined by qPCR with generic and species-specific primers. AVST detected more target species than WDE on 77% of sampling occasions. When comparing the relative abundance of the three European H. annosum s.l. species detected by AVST and WDE, H. parviporum and H. abietinum were found to be overrepresented on wood discs. cHa in November was significantly higher than in May and June, confirming the seasonal pattern typical for temperate Europe. For an accurate and rapid estimation of Heterobasidion primary infection risk, the usage of AVST is highly recommended.

William Frankland: the “grandfather of allergy”

Photo credit: Imperial College London William Frankland (“Bill”), the British clinical allergist who transformed global understanding of allergies, has died aged 108. He developed the pollen count in order to...

Detection of Airborne Inoculum of Hymenoscyphus fraxineus and H. albidus during Seasonal Fluctuations Associated with Absence of Apothecia

Hymenoscyphus fraxineus is an invasive fungal species causing the most serious disease of ashes (Fraxinus spp.) in Europe—ash dieback. The biology of this fungus is not totally elucidated, neither its relation to the saprophytic species Hymenoscyphus albidus, native in Europe. Our study is focused on the description of seasonal spore dispersal of both fungi and its relation to meteorological conditions, which is needed for more precise and effective control of the disease. For this experiment one long time infected mixed forest in the SE Czech Republic was chosen. A seven-day automatic volumetric spore trap and a weather station were installed to continuously sample the aerospora from April to October 2014. In seven periods a rotating arm spore trap was also used to obtain 48-h air samples to compare the efficiency of these two types of air samplers. Air samples were evaluated solely by qPCR with a very low detection limit. Results show co-occurrence of inoculum of both fungi throughout the entire sampling period with peak levels in August. The origin of the inoculum sampled in the periods without apothecia is discussed. Air-inoculum occurrence of both fungi is significantly correlated with each other, suggesting their coexistence in this forest.

Dothistroma septosporum: spore production and weather conditions

Dothistroma septosporum, the causal agent of Dothistroma needle blight is a widespread fungus which infects more than 80 species of coniferous trees through the entire world. Spreading of the infection is strongly affected by climatic factors of each locality where it is recorded. We attempt to describe the concrete limiting climatic factors necessary for the releasing of conidia of D. septosporum and to find out the timing of its spore production within the year. For this purpose we used an automatic volumetric spore trap and an automatic meteorological station. We found that a minimum daily average temperature of 10 °C was necessary for any spore production, as well as a long period of high air humidity. The values obtained in the present study were a little bit higher than those previously published, which may arise questions about a possible changing trend of the behaviour in the development of the Dothistroma needle blight causal agent. We used autoregressive integrated moving average (ARIMA) models to predict the spore counts on the base of previous values of spore counts and dew point. For a locality from Hackerovka, the best ARIMA model was 1,0,0; and for a locality from Lanzhot, the best was 3,1,0.

Sampling pollens

Although early microscopists established the presence of pollens in the air in the 18th century, airborne pollens were not sampled until the end of the 19th century. For many years, the sedimentation slide was the commonest method of assessing airborne pollen concentrations but later, samplers originally developed for sampling airborne bacteria and fungal spores were utilised. In particular, the Hirst automatic volumetric spore trap, which was based on a cascade impactor but additionally allowed collection of the sample onto a moving slide, became the commonest method of pollen sampling. This allowed much more accurate assessments of pollen concentration than had previously been possible and more detailed studies of diurnal and seasonal periodicities. This article evaluates different pollen sampling methods and recently developed techniques for collecting pollen antigens for immunoassay and DNA amplification.

Aerobiological monitoring ofAlternaria fungal spores: a comparison between surveys in 1992 and 1993 and local meteorological conditions

A study of airborneAlternaria spores was carried out over the period from April 1992 to October 1993, in the Rehabilitation Medical Centre of Montescano (PV), using an automatic volumetric spore trap (VPPS 2000 Lanzoni). The evaluation of the air concentration of these spores is becoming ever more important as it is this mycophyte which is the commonest cause of a positive allergy test. In 1993 the concentration ofAlternaria spores was much higher than in the previous year and the period of highest sporulation was different, depending on the different rainfall pattern of the 2 years.

The concentrations of air-borne rape pollen over a crop of oil-seed rape (Brassica napus L.)

SUMMARYThe air over a crop of flowering winter oil-seed rape was sampled for 39 days with an automatic volumetric spore trap. Considerable quantities of rape pollen were caught on most days. Density of pollen showed marked diel periodicity; few grains were caught at night and at mid-day, peaks occurred in late morning and early afternoon. It is concluded that wind plays a considerable role in pollination of the crop.

Air Spora of an Agricultural Farm in Madras, India

Abstract A survey of the air spora of an agricultural farm was carried out continuously from 8 January 1978 till 8 April 1978 with Burkard automatic volumetric spore trap. Twenty-two types of fungal spores representing 22 genera were identified from the catches on the exposed traces. Of these, only spores belonging to 10 genera were frequently recorded. The circadian periodicity and percentage contribution of these ten genera are described in detail. Cladosporium was found to be predominant in the air and contributed 72.9% of the total air spora followed by Nigrospora (7.6%).

Comparative particle recoveries by the retracting rotorod, rotoslide and Burkard spore trap sampling in a compact array

An array comprising 4 intermittent (retracting) rotorods, 3 (“swingshield”) rotoslides and one Burkard (Hirst) automatic volumetric spore trap was operated on an urban rooftop during 70 periods of 9, 15 or 24 hours in late summer. Standard sampling procedures were utilized and recoveries of pollens as well as spores ofAlternaria, Epicoccum, Pithomyces andGanoderma species compared. Differences between paired counts from each sampler type showed variances increasing with levels of particle prevalence (and deposition). In addition, minimal, non-random, side-to-side and intersampler differences were noted for both impactor types. Exclusion of particles between operating intervals by rotoslides and rotorods was virtually complete. Spore trap recoveries for all particle categories, per m3, exceeded those by both impactors. The greatest (7-fold) difference was noted for the smallest type examined (Ganoderma). For ragweed pollen, an overall spore trap/impactor ratio approached 1.5. Rain effects were difficult to discern but seemed to influence rotoslides least. Overall differences between impactors were quite small but generally favored the rotoslide in this comparison. Our data confirm the relative advantages of suction traps for small particles. Both impactors and spore traps are suited to pollen and large spore collection, and, with some qualification, data from both may be compared.

Aerobiological studies based in Derby. I. A simplified automatic volumetric spore trap.

A simplified version of the Hirst automatic volumetric spore trap has been developed in Derby for aerobiological studies. In comparative trials, the number of spores retained by the Morrow Brown trap were similar in the case of larger spores such as Alternaria (102%), rather higher in the case of grass pollen (136%) and considerably higher (166--201%) for very small spores such as Sporobolomyces and Tilletiopsis. Impaction efficiency has been improved by using a narrower slit. The trap designed in Derby is simple to produce and presents advantages in design over the Hirst version.

Conidium liberation in Erysiphe graminis: I. Visual and statistical analysis of spore trap records

The effects of various factors upon the liberation of conidia of Erysiphe graminis DC. f.sp. tritici Marschal (powdery mildew of wheat) were investigated, using a Hirst automatic volumetric spore trap and a range of meteorological instruments. The data obtained were analysed by standard visual methods and also by means of the correlation coefficient phi (φ), (ad-bc)[(a + b)(c + d) (a + c)(b + d)]-½, where a, b, c and d refer to the cells of a 2 × 2 table used for the computation of coefficients of association. A digital computer was employed in this analysis. The difficulties and potentialities of such a means of analysis are discussed. Seasonal and diurnal periodicities recorded by other workers were confirmed. Days in which rainfall occurred were profoundly different from dry days, the diurnal periodicity of spore release being obscured. Wind, rainfall, surface dryness of the host leaves, high temperatures and low relative humidities were positively associated with spore liberation. Rainfall was independent of the other phenomena, which occurred as a complex. Onset of rain and wind were shown to be more important than continuation of either.

Effects of temperature, humidity and caging on the concentration of fruit pollen in the air

The amount of air-borne pollen was measured continuously over several days at peak flowering in apple, peach, and cherry orchards using an automatic volumetric spore trap. The maximum number of grains of pollen per m3 recorded in the apple, cherry, and peach orchards were 68, 48, and 13 respectively High concentrations were associated with high ambient temperatures and low relative humidities. In a second experiment, pollen concentrations were measured over five days inside and outside a 1/10- inch mesh insect-proof cage placed in a lemon orchard. Significantly (P<0.01) more pollen was recorded outside the cage than inside.

Epidemiology of tea blister blight ( Exobasidium vexans) : II. The diurnal and seasonal periodicity of spores in the air over a tea estate

Using an automatic volumetric spore trap for sampling air at 1 m. above ground in a field at the Tea Research Institute, Talawakele, the diurnal and seasonal periodicity of spores of Exobasidium vexans Massee were followed. The seasonal periodicity was not very marked. The highest catches were recorded in May and June and again in November, coincident with the two monsoons (the South-West and the North-East) when the spores reached mean concentrations of 10,500 and 9600/m.3 air, respectively. The lowest catch (2000/m.3) was recorded in March. Two-hourly concentrations obtained on 24 days in July indicated a very pronounced diurnal rhythm in the spore content. The highest concentration was reached between midnight and 04.00 hr. and in this respect E. vexans seems to resemble several other Basidiomycetes which show a similar nocturnal pattern. The diurnal periodicity could, however, be greatly altered by weather conditions. For instance, a heavy thunderstorm at approximately 13.00 hr. on 25 and 26 October, resulted in two peak catches on those 2 days, high concentrations occurring in the first and second hours after the onset of rain, and again in the early hours of the morning. Prolonged rain, on the other hand, generally resulted in a drop in the mean daily catch.

The dispersal of colidia of Sclerotinia fructicola (Wint.) Rehm.

The dispersal of conidia of Sclerotinia fructicola (Wint.) Rehm. was studied in a peach orchard and in the laboratory, with the use of traps for water-borne spores and an automatic volumetric spore trap. In the orchard, little aerial dispersal was detected by using a trap less than 10 ft from the nearest trees, but large numbers of spores were dispersed by rain falling on sporulating blossoms. In the laboratory, splash droplets from a drop of water falling onto a sporulating fruit or glass slide dusted with conidia were recorded at distances of up to 36 cm. More than two-thirds of the droplets contained spores, the numbers ranging from 3 to more than 7000 per droplet. Aerial dispersal was detected in the laboratory when sporulating peach fruits were placed 3 ft from the volumetric trap. Dispersal was greatest at minimum humidities and maximum air temperatures. The results of the experiments suggest that splash dispersal is more important than aerial dispersal of conidia of S. fructicola in the epidemiology of brown rot of stone fruits.

Incidence of conidia of Erysiphe graminis in the air over a mildew-infected barley field

Air over circular plots of mildew-infected, spring-sown barley was sampled with a Hirst automatic volumetric spore trap in the summers of 1955 and 1956 at the Imperial College Field Station, Ascot, Berks. Air-borne conidia of Erysiphe graminis DC. displayed a regular pattern of diurnal periodicity with the daily peaks at about noon. Simultaneous observations were made in 1956 on the growth phases of the barley plants, the incidence of mildew in the plot, and the number of E. graminis conidia in the air. A sudden increase in conidia was observed in mid-June, with the outbreak of the disease in the plot, when the barley plants were in the stem extension phase. In the second half of June, when the crop was passing through the heading phase, the seasonal maximum occurred. In July, when the flowering and ripening phases occurred, very few conidia were caught. They disappeared completely from the air by the end of July when the crop was ripe and the straw dead. Rain reduced the number of conidia in the air to a very low level. In dry weather following rainy spells there was slow recovery; it took about 3–5 days for the counts to reach pre-rain levels. The diurnal periodicity pattern was not affected by rain or by variation in wind speed, but both affected catches quantitatively to some extent. The catches were greatest when strong winds and low relative humidities occurred simultaneously in the afternoon; the highest hourly estimate recorded was 18,300 conidia per m.3 of air.

The summer air-spora of two contrasting adjacent rural sites.

SUMMARY: The air in a valley near a stream and in an exposed site on a small hill at Silwood Park, near Ascot, Berkshire, was sampled from 14 May to 25 September 1958 at half a metre above the ground by a Hirst automatic volumetric spore trap. Seasonal periodicities of 26 categories of fungus spores and 7 categories of pollen grains are given as 6-day running means of the daily average number of spores per cubic metre of air. Estimated hourly concentrations of spores for 6 consecutive days are given for three fungus spore types and two pollens. The diurnal periodicity is given for these groups. There were 2–6 times more spores at site S near the stream than at the exposed site M. There were 4.9 times more spores of ascomycetes at S than at M. 3 times as many spores of basidiomycetes but only 1.4 times as many from fungi imperfecti. The proportion of the different types of spores at the two sites varied; 14% of spores at S were from ascomycetes, 7% at M; 17.5% of those at S were from fungi imperfecti and 32% of those at M. Tree pollen grains were equal in number at both sites but there was 2.8 times more grass pollen and 6.5 times more weed pollen at S than at M. Urtica pollen was 8.1 times as common at S and made up 55% of the total pollen in that area, but only 24% of the total at M, mainly because of the local abundance of nettle plants. The results suggest that the ecology of an area has a major influence on its air-spora through local flora and microclimate.

Some components of the air‐spora in Jamaican banana plantations

SUMMARYThe air in several Jamaican banana plantations was sampled from July 1960 to September 1961 with an automatic volumetric spore trap. In dry weather, many fungi showed typical diurnal periodicity. Group I fungi (Deightoniella, Nigrospora, Cordana, Corynespora, Zygosporium and Zygophiala) first appeared shortly after 06.00 hr., reached a peak before 09.00 hr. and then showed a rapid fall. Group II fungi (Cladosporium, Alternaria, Curvularia, Cerebella, Pithomyces, Periconiella, Memnoniella, Ustilago and others) and pollens had peak concentrations between 09.00 and 14.00 hr. Groups I and II formed the majority of the spore catch during daylight, but they were practically absent between 20.00 and 06.00 hr. Group III fungi (represented chiefly by ascospores, especially of Leptosphaeria spp., basidiospores and splash‐dispersed types) first appeared near 20.00 hr., attained a maximum between midnight and 06.00 hr. and a minimum during daylight. In dry weather, Cladosporium conidia accounted for 23% of the total catch; coloured fusiform spores for 18%; coloured basidiospores for 16%; unclassified minute spores (including Sporobolomyces) for 14%; and Deightoniella only 0.2%.During rain, the typical dry‐air‐spora decreased and was replaced to varying extents by group III ascospore types and splash‐dispersed spores. When, after rain, the plantation dried out during daylight, group III fungi decreased while groups I and II briefly reappeared before the typical night‐time flora developed. When rain was continuous during daylight, groups I and II were rare; ascospores and splash‐dispersed spores dominated the traces. All fungi occurred in low concentrations during heavy rain, periods of drought and strong wind. With rain or under‐tree irrigation or both, the following days had varying increases of all group I fungi and certain group II fungi, probably because favourable humidity conditions caused increased sporulation.

Dispersal of conidia of Cordana musae (Zimm.) Höhnel in Jamaican banana plantations

SUMMARYThe air in several Jamaican banana plantations was sampled from July 1960 to September 1961, using an automatic volumetric spore trap. Conidia of Cordana musae, a banana leaf pathogen, display regular diurnal periodicity, the peak concentration of conidia per m3. of air normally occurring near 07.00 hr. The period of most rapid liberation corresponds with that of rapidly increasing temperature and decreasing R.H. Relatively low daily mean conidium concentrations (< 20 per m3.) were recorded in St Catherine where the incidence of Cordana leaf spot was low. Appreciably higher counts were obtained at Bodles where the trap was operated close to diseased plants. With few exceptions, nights when humidity exceeded 95% R.H. for less than 5 hr. were followed on successive days by concentrations lower than c. 25 conidia per m3. Rainfall and irrigation, resulting in longer periods of high R.H. at night, were usually followed by markedly higher concentrations (50–400 conidia per m3.). The highest hourly estimate recorded was c. 4000 conidia per m3.

Fruit‐spot (‘speckle’) of Jamaican bananas caused by Deightoniella torulosa (Syd.) Ellis

SUMMARYUsing an automatic volumetric spore trap, variation in the atmospheric spore content of Deightoniella torulosa (Syd.) Ellis, the cause of banana fruit ‘speckle’, has been studied in a banana plantation during the period September 1960‐February 1961. Dry weather was characterized by relatively low daily mean spore concentrations of 50–200 spores/m.3of air. Much higher concentrations (2000–7000 spores/m.3) were recorded shortly after rainfall or periods of under‐tree irrigation.Considerable reduction in concentration occurred after the removal from the plantation of decaying leaves and other banana ‘trash’, such tissues being the major source of inoculum of D. torulosa. Similarly, spore counts in trash‐free plantations were consistently lower than those in ‘dirty’ ones. Although the evidence is not conclusive, since it was not possible to provide controls, it seems likely that good plantation hygiene is a major factor in reducing the air spore content of the fungus.In the plantations, the large conidia of D. torulosa have a short air‐borne phase, probably because sedimentation and/or deposition rates are high. This results in relatively short horizontal dispersal distances.

Fruit-spot (‘speckle’) of Jamaican bananas caused by Deightoniella torulosa (syd.) ellis : III. Spore formation, liberation and dispersal

The air in two Jamaican banana plantations was sampled during the period 19 July–5 October 1960 at 3 m. above ground with a Hirst automatic volumetric spore trap. Each day's slide was scanned and conidia of Deightoniella torulosa were counted at positions representing 2-hourly intervals. In both plantations there was a clearly defined diurnal periodicity, the peak concentration of spores/m. 3 of air normally occurring near 08.00 hr. and then decreasing to a low level between 12.00 and 24.00 hr. each day. The period of most rapid liberation (06.00–10.00 hr.) corresponds with that of rapidly increasing temperature and decreasing R.H. This may be due to a previously undescribed active discharge mechanism operating under conditions of decreasing vapour pressure. In plantation A, which was surface irrigated, daily mean concentration varied between o and 58 spores/m. 3 when the previous 2–12 days were rainless. After 0·55 and 2·55 in. rain, concentrations of 377 and 536 spores/m. 3 , respectively, were recorded : the highest 2-hourly estimate recorded was 5280 spores/m. 3 . In plantation B, where under-tree irrigation was practised, successive irrigation periods (each of 48 hr.) were associated with considerable increases in spore concentration; rainfall resulted in similar large increases. The highest daily mean concentration recorded was 7115 spores/m. 3 , while the highest 2-hourly estimate was 72,335 spores/m. 3 at 08.00 hr. on 8 September—approximately 12 hr. after cessation of irrigation. As the plantation dried out after irrigation or rainfall, spore concentration decreased rapidly within 2–3 days. Both rainfall and irrigation spray resulted in heavy sporulation of D. torulosa on banana-leaf ‘trash’; this helps to explain the increased atmospheric spore concentrations referred to above. There was a marked increase in incidence of fruit-spot during under-tree irrigation periods and when rainfall caused the plantation r.h. to remain high for more than 12 hr. during the day. Incidence of fruit-spot in plantation B was higher than in A; this was related partly to the greater numbers of dead banana leaves in the former, and partly to the favourable effects of under-tree irrigation on sporulation, spore germination and infection.