3rd International Symposium on Weeds and Invasive Plants
October 2-7, 2011 in Ascona, Switzerland
Common Ragweed (Ambrosia artemisiifolia L.) in Ticino: development and
approaches.
1 Cantonal
Rossinelli M.1,* and Colombi L.1
Phytosanitary Service, Bellinzona (TI), Switzerland
ABSTRACT: Since 2003 Ambrosia artemisiifolia is considered in Canton Ticino as a problematic plant, because of its allergenic pollen and its high potential of reproduction. The cantonal authorities decided in 2004 to set up a working group (“Gruppo di Lavoro Ambrosia”) aimed to study this invasive plant and to coordinate the strategies for slowing down its spread in the region. Since 2006 A.
artemisiifolia is officially part of the quarantine organisms in Switzerland, and since 2007 there are
cantonal directives to cope with this weed. The main purpose of these efforts is to avoid the production
of inflorescences what may prevent pollen and seed dispersal. In the last 7 years many approaches
have been adopted. First of all, private and public institutions have been sensitized and informed.
Second, a mapping and monitoring of past, current, and potential outbreaks have been realized. Finally, A. artemisiifolia has been fought by grubbing, repeated cutting or herbicide spraying, depending on
the location and the density of the plants. During the years the geographical presence of A. artemisiifolia increased in Ticino, moving from the South to the North. There was a general increase of outbreaks, but for each location the trend is a decreasing plant density with time. Past fighting activities
showed some positive results. However, the natural and anthropogenic spread of A. artemisiifolia
seems not to be retarded. In the future there should be a better control of artificial movements of soil
masses in Ticino, in order to avoid further seed dispersal.
KEYWORDS: Ambrosia artemisiifolia, quarantine organism, Switzerland, fighting strategy.
1
INTRODUCTION
Common ragweed is an invasive plant,
causing health problems worldwide. In Canton
Ticino its presence is known since 2003, when a
first survey conducted by the Swiss Department
of the Environment, Transport, Energy and
Communications and the Natural History Museum of Lugano highlighted the presence of 77
spots of A. artemisiifolia. This result suggests an
earlier presence of the weed in Ticino (Ciotti et
al., 2004).
2004 the cantonal authorities set up a group
of experts (Gruppo di Lavoro Ambrosia) to study
the weed and to elaborate suitable fight strategies.
2
OBJECTIVES
The main objective of the fighting activities is
to avoid flowering A. artemisiifolia plants, in order to reduce damages caused by its pollen and
to limit its geographical expansion.
______________________
Corresponding author address: Marta Rossinelli,
Servizio fitosanitario cantonale, viale Stefano
Franscini 17, 6500 Bellinzona, Switzerland;
tel: +41 91 814 35 57; fax: +41 91 814 44 64;
email: [email protected]
3
APPROACHES
3.1 Policy
2006 the Swiss government decided to include A. artemisiifolia in the vegetal protection
decree (Ordinanza sulla Protezione dei Vegetali,
2010) as a quarantine organism. With this document the property, as well as diffusion and multiplication are officially forbidden. In addition to it,
everyone, who doubt or know the presence of
this plant has to contact immediately the responsible cantonal service. The fight against
such a quarantine organism is in fact obligatory.
2007 the canton Ticino published guidelines
in order to organize the fight against A. artemisiifolia (Direttive concernenti la lotta contro
l’Ambrosia artemisiifolia, 2007). According to
these guidelines every citizen and every institution has to report the presence of A. artemisiifolia and eradicate the plants present on his property. Municipalities, public and private entities
have to supervise their district and eradicate the
plants. Composting is absolutely banned. All
plants found have to be mapped and monitored
in the following years.
Since 2007 the canton Ticino is actively
fighting A. artemisiifolia through sensitization,
monitoring and active eradication. The responsible person belongs to the cantonal Phytosanitary Service, which is part of the Department of
Agriculture. Regarding the national highways
there is the Maintenance Services that deals
with monitoring and eradication.
3rd International Symposium on Weeds and Invasive Plants
October 2-7, 2011 in Ascona, Switzerland
3.2 Sensitization
Different sensitization-days have been organized with the collaboration of the Swiss Research Centre for Agriculture (Agroscope ACW).
Some of them took place in city squares, some
others in the field, in schools or other education
centres.
Many written notices have been published
on newspapers, specialized magazines of the
building sector or on the weekly phytosanitary
reports and flyers have been distributed.
Figure 2. Monitoring map (2010) of ragweed in
Ticino. Black points represent sites, where A.
artemisiifolia has been found.
Figure 1. Children eradicating ragweed under a
highway in the Southern part of Ticino during a
sensitization-day.
3.3 Monitoring
Since 2007 existing Ambrosia spots in Ticino have been mapped and registered in a geographical information system. Every year all
flash points are re-monitored and the new plant
number is registered.
Potential habitats, like border of crop fields,
soil yards, dumping grounds, building sites, and
in general abandoned sites or naked soils are
also stand over.
3.4 Active eradication
The suggested fight method depends on the
plant quantity and on the location of the spots. In
fact if there are only few plants, the advise of the
Phytosanitary Service is to eradicate them. In
the case of more than 100 plants there are two
ways: eradication or repeated cuts, which can
lead to re-growth and reformation of flowers.
In agriculture the most common method is
the mechanical control or in some cases also
herbicides.
Along highways big populations have been
treated with herbicides, while small populations
have been eradicated.
4
RESULTS
Nowadays citizens are aware of the problematic, actively contacting the Phytosanitary
Service for doubts or for announcing new flash
points.
Flash points are mostly located on the main
roads of Ticino (see figure 2). Their number continuously increases with time. At the beginning
in 2003, 77 spots have been recorded, 144 in
2006 and 268 in 2007, when the first systematic
monitoring took place. The number increased
also in the following years: 354 in 2008, 383 in
2009 and 412 in 2010.
The presence of A. artemisiifolia has always
been stronger in the southern part of Ticino. In
2010 77% of the flash points were in the southern part of Ticino and only 23% in the northern
part (Figure 2). Despite that, this percentage
increased with time (in 2003 the percentages
were 87% in the South and 13% in the North).
The positive aspect is that generally, for
each flash point, the number of plants decreases with time.
5
CONCLUSION
The main dispersion way of A. artemisiifolia
in Ticino seems to be the traffic. This confirms
that the ragweed, like most other invasive
plants, spreads thanks to human activities.
Artificial soil movement during construction’s
activities is also a big problem for the diffusion of
3rd International Symposium on Weeds and Invasive Plants
October 2-7, 2011 in Ascona, Switzerland
ragweed in the territory. Very often A. artemisiifolia is found in construction areas. An example
is the spot number 412 (see figure 2), where
natural dispersion can be excluded. Ragweed
has been found in a place where a house was in
construction: most probably introduced with the
seed-infected soil used.
Ambrosia dispersion during the last years
didn’t stop, but the measurements token by the
Swiss government and the canton Ticino may
have contributed to slow down its diffusion and
to reduce its density in the hotspots.
There is still a lot of work to do to cope this
weed, especially regarding soil movements.
6
REFERENCES
Ciotti, V.; Maspoli, G.; Köhler, B.; Ambrosia
artemisiifolia Monitoring im Kanton Tessin, 2004,
10 pp.
Direttive concernenti la lotta contro l’Ambrosia
artemisiifolia, 2007.
Ordinanza sulla Protezione dei Vegetali, 2010. Swiss
law: 916.20, 114 pp.