Common ragweed: a threat to environmental health in Europe.

Common or short ragweed (Ambrosia artemisiifolia L.) is an annual herb belonging to the Asteraceae family that was described by Carl Linnaeus in the 18th century. It is a noxious invasive species that is an important weed in agriculture and a source of highly allergenic pollen. The importance placed on A. artemisiifolia is reflected by the number of international projects that have now been launched by the European Commission and the increasing number of publications being produced on this topic. This review paper examines existing knowledge about ragweed ecology, distribution and flowering phenology and the environmental health risk that this noxious plant poses in Europe. The paper also examines control measures used in the fight against it and state of the art methods for modelling atmospheric concentrations of this important aeroallergen. Common ragweed is an environmental health threat, not only in its native North America but also in many parts of the world where it has been introduced. In Europe, where the plant has now become naturalised and frequently forms part of the flora, the threat posed by ragweed has been identified and steps are being taken to reduce further geographical expansion and limit increases in population densities of the plant in order to protect the allergic population. This is particularly important when one considers possible range shifts, changes in flowering phenology and increases in the amount of pollen and allergenic potency that could be brought about by changes in climate.

Examination of common ragweed's (Ambrosia artemisiifolia L.) allelopathic effect on some weed species.

In the last decades the importance of some weed species increased in Hungary. The common ragweed (Ambrosia artemisiifolia L.) also belongs to this group. The allelopathic effect of watery extract made from different plant parts of common ragweed (air dried leafy shoots, seeds) were studied on the germination and growth of some weed species. The extracts were prepared with tap water, chopped dry plant materials were added to water and 24 hours later the material was filtered. The germination took place in a Binder KBW type thermostat in dark. 25 seeds were put into one Petri-dish, adding 15 ml plant extract to each in four repeats. The timing of germination was checked in every two days and the rate of growth was estimated after a week, by counting the numbers of germinated seeds and measuring the length of the radicle and plumula. The measured data were statistically analysed and the effect of extracts on germinating ratio and seedling length were evaluated.

Airborne grass and ragweed pollen in the southern Panonnian Valley--consideration of rural and urban environment.

The aims of this study were to describe and compare the characteristics of grass and ragweed airborne pollen in rural and urban areas in the southern Panonnian Valley. Airborne pollen data were collected by using Hirst type volumetric samplers simultaneously in rural and urban localities. If rural and urban environment are considered, both grass and ragweed daily pollen concentrations showed a significant degree of association. Observed parameters (pollen index, maximum daily concentration, number of days during which the pollen is recorded in the air and start day of main pollen season), showed year-to-year variations for both grass and ragweed aeropollen. Average values of these parameters were higher in the rural environment, but the difference was statistically significant only for grass pollen index. Such a low difference indicates the possibility for conducting dose response clinical trials based on data obtained from one sampling station. The least year-to-year variations as well as the least difference between rural and urban environment, have been observed in the case of start date of the MPS. Such a situation suggests the possibility for using data obtained in one type of environment for the development of long-term forecast models for an entire region.

Ragweed (Ambrosia) progression and its health risks: will Switzerland resist this invasion?

The purpose of this article is to alert physicians for the environmental and health threats of Ambrosia artemisiifolia (common ragweed) in Switzerland. Switzerland borders several heavily ragweed colonised areas. Up to 12% of the population suffers from allergies (hay fever, asthma) to ragweed pollen in these areas. Switzerland is beginning to be invaded by this plant. Currently, the ragweed pollen counts are still low but can reach local peaks that induce symptoms in allergic individuals. Ragweed allergy, however, is still rare in Switzerland. Because the amount of ragweed pollen was increasing in the last few years, identification and surveillance of ragweed plant foci was started. Colonisation is currently systematically monitored in Geneva and southern Tessin. Major accumulation of ragweed foci have been detected in the canton of Geneva, the western shore of the lake of Geneva belonging to the canton of Vaud, and in the southern part of the canton of Tessin, aside from minor foci registered all over Switzerland. The routes of ragweed invasion are presented and discussed. Current measures of ragweed containment and needs for the future are presented. The urge for these measures at an early stage of ragweed spread is underlined by the impracticability of eradication in highly colonised areas. The costs of preventing ragweed spread in Switzerland are likely to be several magnitudes lower than the treatment of a significant percentage of the Swiss population for ragweed pollen allergy. Because areas can change from low to heavy ragweed colonisation within a few years, the current window of opportunity to prevent further colonisation by ragweed should not be missed.