© Benaki Phytopathological Institute
Marinan-Arroyuelo
et al.
62
of the benefit/cost ratio, at actual farmer’s
prices, when using a pre-emergence herbi-
cide (pendimethalin) versus hand weeding
and alternative herbicides for weed control
in specific crops. The benefit/cost analysis
has been used by some researchers to deter-
mine if a weed management practice is eco-
nomically justifiable (Culliney, 2005; Magani
et al.
, 2012). The hand weeding labour return
value was also determined.
One objective of this study was to ap-
praise the importance of using a proper
pre-emergence herbicide for weed control
in crops of Southern European countries,
since appropriate benefit/cost studies have
not been done so far. In these countries, the
variety of weed species is in general great-
est and climatic conditions favour their pro-
longed emergence, thus northern Europe-
an farmers are the ones mostly affected by
the limited availability of pre-emergence
herbicides. Four diverse crops were there-
fore selected that are important for South-
ern European countries, namely processing
tomatoes, onions for dry bulb production,
cotton and broccoli. Furthermore, mar-
ket prices for processing tomatoes (WPTC,
2012), cotton (USDA, 2012) and onions (Eu-
rostat, 2012) are affected by strong interna-
tional competition and Southern European
farmers continuously try to keep weed con-
trol and production costs low so that they
do not loose access to market. An important
minor crop, broccoli, was also included in
the study since weed control in minor crops
is even more difficult due to the unwilling-
ness of herbicide manufacturers to seek reg-
istration for such crops (Gast, 2008).
Pendimethalin was used as the refer-
ence pre-emergence herbicide in this study,
as it is known for its good efficacy on many
weed species with a good duration of con-
trol and no resistance problems. Further-
more, it is one of the few members of the
low resistance-risk group of the dinitroani-
line or K1 herbicides-inhibiting microtubule
assembly (HRAC, 2014), that have remained
available to the farmers (EU, 2003) and are
expected to play an important role in the
anti-resistance strategy in next years. It is
worth mentioning that, although dinitroa-
niline and other microtubule-inhibiting her-
bicides have been used for several decades,
they have selected resistance in only 12
weed species (Heap, 2014). This is because
the target-site resistance for the dinitroani-
line herbicides is inherited as a recessive sin-
gle nuclear gene, which makes this mecha-
nism of resistance more difficult to evolve
as the initially rare heterozygous individuals
are killed at normal herbicide dose. Also, this
helps explain the limited evolution of this
mechanism of resistance, especially in cross-
pollinated species (Powles and Yu, 2010).
Pendimethalin is registered and used in
many major crops and it is the only herbi-
cide registered in as many as 20 minor crops
in the Southern European countries. The
reason for its broad use as a selective her-
bicide is the limited acropetal translocation
from the root tissues to the above plant or-
gans (products), which prevents the pres-
ence of pendimethalin residues on the
products above the prescribed MRL limits
(Sondhia, 2013; WSSA, 2007). In addition, its
strong adsorption on soil colloids reduces
its leaching potential (it is practically immo-
bile in the soil) and makes this herbicide en-
vironmentally friendly regarding water con-
tamination (WSSA, 2007). Being one of the
few herbicides registered in several crops,
the scenario of a possible withdrawal of
these pendimethalin uses from the market
has to be evaluated from the farmer’s eco-
nomic perspectives. The second objective
of this study was therefore to provide a ba-
sis for such an evaluation.
Materials and methods
General
For the purpose of this study field trials
were conducted in major growing areas for
the respective crops in either Greece or It-
al
y
. Treatments in all trials included pendi-
methalin (at one or two rates) as registered
and commonly used by farmers, an untreat-
ed control and a hand-weeded control. De-
pending on the crop, treatments also includ-
