Paul Comtois

Principles of the Atmospheric Pathway for Invasive Species Applied to Soybean Rust

Abstract Aerial transport alone is seldom responsible for the introduction of nonindigenous species into distant regions; however, the capacity to use the atmospheric pathway for rapid spread in large part determines the invasive potential of organisms once they are introduced. Because physical and biological features of Earths surface influence the routes and timing of organisms that use the atmospheric pathway, long-distance movement of aerobiota is largely regular and thus predictable. Soybean rust (Phakopsora pachyrhizi), potentially the most destructive foliar disease of soybean, recently invaded North America. The concepts presented in this article form the basis of the soybean rust aerobiology prediction system (SRAPS) that was developed to assess potential pathogen movement from South America to the United States. Output from SRAPS guided the scouting operations after the initial discovery of soybean rust in Louisiana. Subsequent observations of P. pachyrhizi in the southeastern United States provide validation of the modeling effort.

Pollen counts statistics and its relevance to precision

In the day to day management of pollen counts from aerobiological samples of national networks, only a small proportion (usually from 12 to 15%) of the daily microscope slide is read. It is generally believed that, otherwise, too much time will be spent reading slides for a minimal increase in precision. Different networks use different slide sampling methods (longitudinal, transverse or at random) and a different number of lines are routinely read. However, the topic of the precision of the different pollen count strategies has seldom been the object of serious investigation. In this study, the precision of different sampling methods of 12 pollen types was investigated by: a) counting pollen grains over the whole slide (3 slides per taxa), b) spatially (i.e. microscope field per microscope field) recording over the 3120 fields found at 400× the location of each pollen grain, c) sub-sampling, by macro procedures, this population by selecting a number of transverse (1 to 48) or longitudinal (1 to 20) lines, or a number of random fields (90 to 2340), so that between 0.96 to 46.15% (transverse), 3 to 66.6% (longitudinal) or 3 to 75% (random) of the whole slide was artificially counted. Between nine and twelve procedures were built per reading strategy. The error found is much higher than what is normally believed, and it was significantly correlated with the abundance of a pollen taxa on the sampled slide. It is only with a total count over 1000 (corresponding to a concentration of above 500 m−3) that the mean error of 4 longitudinal lines (or 13.3% of the slide), the standard protocol of both the Italian Association of Aerobiology (AIA) and the Spanish Aerobiology Network (REA), was always below 30%.

A predictive study of cupressaceae pollen season onset, severity, maximum value and maximum value date

In this paper Cupressaceae pollen season onset, severity, maximum value and maximum value date, have been studied for 15 consecutive years (1982–1996). The data set was obtained using a Hirst spore-trap (Burkard Manufacturing). In order to determine the influence of the previous months’ meteorological variables on Cupressaceae season’s parameters, the sums of maximum, average and minimum temperatures, and total rainfall for the months of October, November and December were used as independent variables in predictive formulae built by multiple regression analyses. The variance explained percentage by regression analyses varied between 60 and 87%. Total rainfall in the months prior to anthesis and temperature (particularly minimum temperature) are important factors to consider in forecasting models of Cupressaceae pollen season parameters, but meteorological conditions at the time of pollen production are also important and can modify the pre-established potential of pollination.

Tree pollen viability in areas subject to high pollutant deposition

SummaryThe wet deposition process, including fog, is a major pathway of acidic pollutants from the atmosphere to the biosphere. Pollen grains are known to be sensitive biological indicators of pollution at this interface. In southern Québec, pollen viability of three hardwood species (sugar maple, white and yellow birch), was significantly reduced above the mean cloud base height (≈600 m) for two successive years (1987–1988) at two mountain sites (Roundtop and Tremblant). Ozone concentrations, fog water and precipitation pH values over the sampling periods are discussed.

The effect of meteorological parameters on diurnal patterns of airborne olive pollen concentration

Aerobiological studies carried out in the atmosphere of Granada using a Hirst-type volumetric spore trap during the period 1993-1996 show that there is not a single diurnal pattern for olive pollen (Olea europaea L.) over the course of the main pollen season. Examination of the behaviour of airborne olive pollen concentration allows the establishment of either regular (54.4% of the studied days) or irregular (45.6% of the time) patterns of diurnal variation. On a given day, the pattern found will depend on a combination of different factors: the origin of the captured pollen (either local or regional), source distribution in relation to the pollen sampler, topography, and different meteorological variables (mean air temperature, sunshine hours, total rainfall, relative humidity, wind speed and direction, and periods of calm). Regional sources were significant contributors to city centre pollen concentrations when moderate (< 10 km/h) winds from the 4th quadrant and warm temperatures (19-26 C) allow swift transport from the W-NW of the province.

Aerobiology: coming of age in a new millennium

Aerobiology has experienced substantial development over the past 150 years. We have come far from the “Golden Age of Aerobiology” (1861–1882), then called Atmospheric Micrography, when the hunt for airborne organisms that carried disease was at its peak. We have progressed beyond the exciting 30’s and 50’s, when new sampling methods were invented and when airborne measurements around the globe and through stratospheric balloon ascents were the rage. We have witnessed a rapid proliferation of aerobiology researchers throughout the world and in new fields of science. Since the 1986 Basel International Congress on Aerobiology, we have seen a shift in the organization of aerobiological activities from studies conducted by individuals to team efforts, in large part due to the advent of structured national monitoring networks. Yet, it is our belief that aerobiology has reached a “plateau” in its scientific development; aerobiological measurements are now more frequent than ever before in history, but new hypotheses and interpretations in aerobiology are too scarce. It is obvious from journal articles and conference proceedings that many aerobiological studies are essentially repetitive enterprises focused on monitoring and describing temporal and spatial variations in numbers and types of aerobiota. Although these activities are important and can be critical to the well-being of humans, crops and livestock, and the environment, we fear that if this is the dominant focus of aerobiological activity, the attractiveness of our field to younger generations of scientists will suffer. So, how do we put challenge back into aerobiology? How can we construct a springboard into the

Pollen capture media: a comparative study

Research laboratories, part of international aerobiological networks are often using different collection media on their exposed tape (or slides). However, their relative pollen capture efficiency has rarely been tested. A single Hirst-trap was used, in Bologna, in February and March 1993, for this experiment. Melinex tapes were divided longitudinally in two equal parts, so that two different media could be tested simultaneously. The tested media were: gelatine/glycerine, hexane/vaseline, silicone/carbon tetrachloride, and paraffin. Each comparisons were repeated on 4 different days. At the time of the sampling, the dominant airborne particles were Cupressaceae andCladosporium. The differences between the different media were non-significant (meanF of different days of 1.720, mean probability of 0.241 (min. of 0.077, max. of 0.356)). The highest probabilities of a significative difference all involved glycerine/gelatine either in comparison with paraffin (0.76), with silicone (0.75), or with vaseline (0.75), while the lowest was for the couple silicone-vaseline (0.59). In general, even if these differences were non-significant, gelatine underestimated spore counts in comparison to silicone, but overestimated them if compared to vaseline or paraffin. However, vaseline looked more efficient then silicone for spore capture. For pollen counts, the same ratios were found, except for the couple silicone-gelatine, which has given similar results. The lowest differences were found withAlternaria andDreschlera, while the highest were found withCladosporium andEpicoccum. The relationship between spore diameter and differences between media was highly significant (τ=−0.786,P=0.027). This was not the case for pollen, withPopulus andAlnus giving the highest differences, andBetula andUlmus the lowest (τ=0.048,P=0.873).

Allergenic exposure, IgE-mediated sensitization, and related symptoms in lawn cutters

AIMS The aims of the study conducted on lawn cutters were: (1) to evaluate exposure to pollens and molds; and (2) to assess the prevalence rate of IgE sensitization and symptoms in relation to exposure to pollens and molds. METHODS Environmental assessment was done with the use of personal samplers on eight workers. Our population consisted of 181 municipal park workers, including 128 lawn cutters and 67 control subjects (blue-collar workers in the hospital). A questionnaire was administered, as well as skin prick tests with seven common inhalants including pollens and eight grass molds. The main outcome variables were grass or mold sensitization (at least one of eight molds) and work-related rhinitis, conjunctivitis, and rhinoconjunctivitis. Atopy and exposure to park-related allergens, as well as sensitization to grass pollens, were considered as explanatory factors. Smoking was taken into consideration as a covariant. Both presence and duration of occupational exposure to park-related allergens were considered as parameters of exposure. Duration of exposure (months x years of exposure as lawn cutters) was used as a continuous or as a categorical variable. RESULTS Environmental monitoring showed that the concentration of pollens and molds decreased in magnitude from samples collected close to lawn cutters faces, short distance away in parks, and in the general environment. There was no difference in the prevalence rates for atopy between lawn cutters (32%) and control subjects (37%). Sensitization rates to grass pollen were also similar in lawn cutters (18%) and in control subjects (22%). However, there was a tendency for prevalence rates of sensitization to molds to be greater among lawn cutters (12% to Alternaria) compared with control subjects (5%). In the logistic model atopy was significantly related to grass sensitization (odds ratio [OR] = 7.2), mold sensitization (OR = 9.3), and sensitization to Alternaria (OR = 5.8). Grass sensitization was a significant risk factor for park-related rhinitis (OR = 5.8), conjunctivitis (OR = 5.0), and rhinoconjunctivitis (OR = 9.4). Exposure for 12 years or more was associated with rhinoconjunctivitis with an OR of 4.1 (95% confidence interval, 1.0-16.7). Smoking was not significantly related to any outcome. CONCLUSION We conclude that among lawn cutters exposure to pollens and molds is higher than in the general population, atopy is the main determinant of sensitization to these aeroallergens, and sensitization and, to a much lesser extent, exposure to grass are determinants of symptoms.

Biogeography and bioclimatology in pollen forecasting

A comparative study of the atmospheric pollen content in two cities, located at similar latitudes, though in different continents, was undertaken. Special consideration was given to the meteorological determinants as shown by correlation analyses. In both localities, the contribution of Poaceae to the aerospora was quite distinct and varied from year to year. Analyses were carried out taking into account either years or cities separately or combined, and at two time scales: daily or weekly counts. Maximum temperature was the major meteorological determinant for daily grass pollen concentration values. Owing to its more arid climate, grass populations in Leo´n seem to react more to sunshine hours. Relative humidity and precipitation had a negative influence but at different time scales in the two localities. In Leo´n, they are related to everyday events such as convective storms, while in Montre´al, the same events are related to low-pressure systems that have the same time scale as air masses. We found that wind speed was the only factor that acted differently in Montre´al and Leo´n. In Leo´n, wind speed has the well-known dilution impact, while in Montre´al, it has a positive impact by increasing pollen shedding from the anthers. Wind speed has therefore a stronger influence at two different stages of the aerobiological pathway in both localities.

Louis Pasteur: the first experimental aerobiologist

SummaryPasteur is a well known scientific giant. However, it is not generally known that in less than a year, in 1860, he founded on precise scientific ground a new science: «micrography» (called Aerobiology since Meiers times (1930s). Not only did he definitely made the spontaneous generation theory disappear for ever, he also presented the true nature of the air spora: a limited cloud of solid dust dispersed by air movements and emptied by gravity. In order to prove the discontinuity of the supposely continuous spontaneous generation, he studied different localities at different seasons, and travelled at different heights. By doing so, he discovered most of Aerobiologys principles: 1) the absolute necessity of volumetric sampling; 2) the heterogeneity of the air spora; and 3) the aerobiological pathway (take-off, dispersal, deposition).