Page 19 - Volume 1, Issue 2, July 2008

New plant pests and weeds in Greece 71
(Vovlas & Troccoli, 1996); R. campensis (Vov-
las et al., 1993); and Tylenchus davainei on
citrus and olive trees in Korinthos, olive
trees in Messolongi and English walnut,
chestnut, apricot, almond and peach trees
in Larissa (Vlachopoulos, 1991).
3.1 Concluding remarks
A total of 30 plant parasitic nematode
species have been reported from Greece
since 1990, most of which are known to
be important pests worldwide. Howev-
er, most cases reported herein were spo-
radic incidents and cannot be considered
a threat to their hosts. Based on available
information and experience, the most
important nematode pest that growers
should be concerned about is Globodera
pallida. This is an EPPO A2 quarantine or-
ganism and legislation regarding the pres-
ence of this species, as also G. rostochien-
sis, is very strict, while they both have a
dramatic impact on potato. In seed pota-
to growing areas, when a field is found in-
fested, it is legally forbidden to grow pota-
toes therein and producers should follow
a three-year crop rotation scheme alter-
nating cereals and legumes, while concur-
rently using chemical nematicides. Prior
to replanting potatoes, the field has to be
re-examined for the presence of cysts.
4. Weed species
There is no systematic monitoring in
Greece for introduced plant species and
particularly for their spread as weeds in
cultivated land of major agricultural areas.
Thus, although quite often new records of
plant species are presented in a number
of papers exploring Greek flora, data on
their acclimatization and potential weed-
status is seldom provided.
The plant species presented in this arti-
cle are mostly cases of recently introduced
plant species that became noticeable be-
cause of some reported problems to grow-
ers after their invasion and establishment
as weeds in an agricultural area. New plant
species for which there is no documenta-
tion of having attained a weed status are
not included. Since the presentation is not
based on a systematic survey, the list of
new weed species may not be complete.
The species are discussed in the text
according to the chronological order of
their observation and listed alphabetical-
ly in Table 4.
4.1. Species already acclimatized
In 1990, Giannitsaros presented some
non indigenous grass species which ap-
peared to be in a stage of acclimatization
and with the potential of becoming weed
species in Greece. They were Bromus ca-
tharticus Vahl., Digitaria ciliaris (Retz.) Ko-
eler, Digitaria ischaemum (Schreber) Muhl,
Echinochloa colona (L.) Link, Eleusine in-
dica (L.) Gaertner, Paspalum dilatatum
Poiret, Paspalum distichum L. and Setaria
adhaerens (Forskal) Chiov. (Giannitsaros,
1990). Three of these species, namely Ele-
usine indica, Paspalum dilatatum and Pas-
palum distichum have already spread and
are now regarded as important weeds
in some irrigated crops (particularly lu-
cerne) and in landscape turf throughout
the country. Echinochloa colona has devel-
oped into a minor weed occurring locally
in some areas. Setaria adhaerens probably
occurs as a variant of Setaria verticillata (L.)
Beauv. (Clayton, 1980) which during recent
years has become a very common weed in
many crops throughout the country.
4.2. Species in a stage of acclimatization
In 1994, growers in the Louros village
near Preveza (western Greece) observed
for the first time a new weed that grew
throughout summer in irrigated fields of
maize, cotton and other crops, causing se-
vere problems by climbing on the crop
plants, tying many of them together and