© Benaki Phytopathological Institute
Marinan-Arroyuelo
et al.
70
yield it needed to be supplemented with
some hand weeding (Table 3) or with a post-
emergence herbicide and some hand weed-
ing (Table 2), measures which increased the
weed control costs and decreased the ben-
efit/cost ratio.
With these trials it became clear, there-
fore, that pendimethalin, being a residual
herbicide with a broad weed spectrum (in-
cluding both broadleaf and grass weed spe-
cies) and registered for many crop uses in
Southern European countries, has the po-
tential to provide maximal yield at the best
benefit/cost ratio in many situations
.
In oth-
er situations, in which there may be a need
to combine pendimethalin with supple-
mentary measures in order to get the maxi-
mal yield, the benefit/cost ratio would most-
ly depend on the cost of the supplementary
measures that will be used.
A properly selected post-emergence
herbicide, if available, could be an econom-
ical supplement to pendimethali
n
. Other
researchers have already shown that high
yield in annual crops is better secured if a
pre-emergence herbicide has been used pri-
or to the post-emergence herbicide appli-
cation (Nurse
et al.
2006; Fickett
et al
., 2013).
In all trials of this study, on the other hand,
pendimethalin significantly reduced the re-
quired time of supplemental hand weeding
to avoid yield loss and provided better ben-
efit/cost ratios and labour return values than
using hand weeding alone (which by itself is
not economically justified at current prices in
Southern European countries). Hand weed-
ing may therefore be another economically
justified supplement to pendimethalin.
Furthermore, other specific reasons have
also increased in recent years the impor-
tance of using a pre-emergence herbicide
particularly for the crops examined in these
trials. Most processing tomato growers in
Southern European countries, to achieve a
better management of specific weeds (eg.
Solanum nigrum
), have abandoned direct
seeding and turned to transplanting which
allows the pre-transplant application of a
pre-emergence herbicide (Tei
et al
., 2003).
The onion dry bulb producers, to reduce
production costs and face price competition
in the market, have turned to direct seeding
but with the young onion seedlings being
susceptible to available post-emergence
herbicides they need to use a selective pre-
emergence herbicide for early season weed
control (Tei
et al.
, 1999). In cotton (Giannop-
olitis, 2013), broccoli and other vegetable
crops (Campagna
et al
. 2009), there are no
registered broad spectrum post-emergence
Table 5.
Expected weed control benefit/cost ratio in processing tomatoes using alternative
weed control scenarios*.
Scenarios
Benefit
(€/ha)
1
Cost
(€/ha)
Benefit/Cost
(€/€)
Inter-row cultivations + hand weeding on rows
2
2697.50
650
4.1
PE mulch on rows + herbicides post- transplanting
3
2697.50
476
5.7
Pre-transplanting residual broad-spectrum herbicide
(pendimethalin)
4
2697.50
101
26.7
Pre-tranplanting broadleaf herbicide (oxadiazon)
+ post-transplanting grass herbicide (fluazifop)
5
2697.50
143.5
18.8
Post-transplanting, two herbicide applications (rim-
sulfuron and metribuzin+rimsulfuron)
2697.50
215.8
12.5
* Based on 2011 prices in Greece (first year after decoupling of the EU production subsidies, when the industry paid
for the tomatoes 20 €/ton higher than the previous year).
1
Assuming a 50% gain (32.5 ton/ha) of an average normal yield (65 ton/ha) x 83 €/ton in all scenario
s
.
2
Cost: 200 €/ha for two cultivations + 450 €/ha for two hand weedings.
3
Cost: 350 €/ha for the PE plastic + 96 €/ha for the price of herbicides (metribuzin+rimsulfuron) + 30 €/ha for
application.
4
Cost: 51 €/ha for the price of herbicide + 50 €/ha for the application.
5
Herbicide prices 46+37,5 €/ha and application cost in Greece 30+30 €/ha.
