Page 28 - Volume 7, Issue 1, January 2014

© Benaki Phytopathological Institute
Damalas et al. 26
clay loam (Typic Xerofluvent) with organic
matter 1% and pH 6.68. Because of the un-
even spatial distribution of the weed plants
in the previous year, an area of 1.5 ha was
defined for the observations and the mea-
surements. The area was cultivated mainly
with winter wheat and spring-sown legume
crops. Shortly after weed emergence in the
defined area in late March, 30 solitary plants
of the same growth stage were selected and
their position was marked by long wooden
stakes. The stakes remained until the end of
the survey (i.e. until maturity of the plants
in early July) to indicate easily the selected
plants. Plants that emerged both inside and
outside cultivated area were selected (15
plants from each area). Morphological traits
at different growth stages of the life cycle of
the weed were visually recorded and mea-
sured. Measurements concerned the thick-
ness of the central stem, the length and
width of the lower and the upper leaves, the
length and width of the open flower, the di-
ameter of the closed capsule at maturity,
the number of seeds/capsule, and the plant
height. The above morphological parame-
ters were determined with a portable digital
caliper (of measuring range 0-150 mm and
measurement increments of 0.01 mm).
Identification of the weed was based on
keys and illustrations provided in the book of
Hanf (1983) and in the guide of Cowbrough
and Smith (2009), which are often used for
weed identification. According to our own
observations, the cotyledons are petiolate,
almost round, with entire margins, smooth
and fleshy surface, and with a shallow notch
(indentation) at the tip. The lower leaves are
simple, petiolate (mostly with large stalks),
oval, with small incisions in the leaf margins
(toothed margins), and smooth with brightly
shiny surface (Figure 1). The upper leaves are
simple, petiolate (mostly with short stalks),
narrowly lanceolate to ovate, with margins
coarsely to regularly crenate-serrate, hairy
veins on the leaf underside and large leafy
stipules at the base of the leaf stalks.
The European field pansy is morpholog-
ically similar to and can be often confused
with the species V. bicolor (syn. V. rafinesquei )
and V. tricolor, but in V. bicolor the color of
the flower is pale blue-violet to pale yel-
low in the centre, while the species V. tri-
color has larger flowers, in which the upper
pair of petals are dark blue or purple from
the middle to the edges (Doohan and Mo-
naco, 1991).
Figure 1. Young seedling of Viola arvensis out of crop.
Figure 2. Young seedling of Viola arvensis in a rosette form.
Figure 3. Young seedling of Viola arvensis inside wheat crop.