© Benaki Phytopathological Institute
Weed control benefit to cost ratio with pendimethalin
65
and harvested on May 31, 2011, in a field lo-
cated in Pella (C. Macedonia, N. Greece). Ex-
perimental plots of 36x8 m (8 crop rows)
were used in both experiments.
In both trials, the basic treatments were
the untreated control and pendimethalin
at the two recommended rates (1137.5 and
1365 g/ha). Pendimethalin in these trials was
applied and incorporated the same day be-
fore transplanting of the broccoli.
Supplemental weed
control in all treat-
ments was made with hand weeding three
times, 31, 51 and 73 DAT for the first trial and
30, 45 and 60 DAT for the second trial.
At harvest, the marketable flower heads
were collected from all plants of the central
4 rows in each plot and weighted.
Weed species present in untreated con-
trols (expressed as mean % contribution of
each species in the weed coverage, 30 DAT)
were:
In the first experiment:
Senecio vulgaris
(12%),
Sonchus oleraceus
(12%),
Papaver rhoe-
as
(8%),
Stellaria media
(13%),
Sinapis
spp.
(8%),
Capsella bursa-pastoris
(10%).
In the secondexperiment:
Seneciovulgar-
is
(7%),
Sonchus oleraceus
(8%),
Chenopodi-
um album
(14%),
Stellaria
sp. (15%),
Anthemis
sp. (5%),
Capsella bursa-pastoris
(17%).
Results
1
Tomato trial
Results from the processing tomato trial
are shown in Table 1.
As shown with the yield data, weeds in
this trial caused a yield reduction of over
50%. Pendimethalin (applied pre-transplant)
was sufficient in preventing yield reduction
but s-metolachlor (also pre-transplant) was
not. Yield loss in this trial was also prevent-
ed when hand weeding (three times, total
1
Note:
All prices quoted in this document are re-
tail prices, have been obtained by BASF from public
sources and/or legal sources believed to be accurate
at the time and are not an indication for current or
future prices. Prices have been provided for the pur-
poses of this document only and are not intended to
be a guidance nor recommendation for the purchase
or application of herbicides. Liability for any errors is
hereby disclaimed.
required time 190 hrs/ha) was used by itself
or when s-metolachlor was supplemented
with post-emergence metribuzin (common
practice by farmers) and the required time
of hand weeding (twice, 92 hrs/ha). When
pendimethalin was similarly supplement-
ed with metribuzin and the required time
of hand weeding (twice, 26 hrs/ha) further
yield increase was insignificant.
The best weed control benefit/cost ra-
tio (17.3) in the processing tomato trial was
achieved with pendimethalin when used
alone. A lower ratio of 7.0 was achieved
when pendimethalin was combined with
metribuzin and hand weeding but even this
ratio is much better than that from all other
treatments. The worst benefit/cost ratio (2.1)
in this trial was achieved when hand weed-
ing was used alone.
The hand weeding labour return value
was 10.5 €/ha when hand weeding was the
only weed control method and significant-
ly better, 16.8 and 22.4, when it was used
to supplement the treatments of pendime-
thalin + metribuzin and s-metolachlor +
metribuzin, respectively.
Onion trials
Results from a trial with winter-seeded
onions are presented in Table 2.
As shown with the yield data, weeds in
onion caused a dramatic reduction of mar-
ketable yield. Pre-emergence pendimeth-
alin only partly prevented yield loss in this
experiment due to the presence of a tol-
erant weed species (
Polygonum convolvu-
lus
) and post-emergence oxyfluorfen which
controlled this weed performed better. The
combination of the two herbicide applica-
tions (a usual practice by farmers) did not
further increase yield. Maximum yield in this
experiment was achieved only when the
combined herbicide applications were sup-
plemented with hand weeding.
Hand weeding (twice) was about as ef-
fective as the herbicides
in preventing yield
loss when used alone and contributed to
a significantly better yield when used as a
supplemental treatment to pendimethal-
in or pendimethalin+oxyfluorfen but not
