Agriculture Reference
In-Depth Information
these products have shown an acceptable
degree of efficiency and selectivity on industrial
crops producing higher densities. They have
potential, which should not be discounted.
The last selectivity trials were under-
taken on the following herbicides in 2002:
Etnos Lenazar, Bastille WG, Primus, Nikos,
Dactal W75, First, Nirvana, Boréal and
Calliste. Only Lenazar managed not to dam-
age the hemp, but it also showed no effi-
ciency against weeds. All the others caused
hemp growth to stop.
(a)
10
9
8
7
6
5
4
3
2
1
0
1992 1993 1994 1995 1996 1997 1998 1999
Year
12-Sept
20-Sept
(b)
45
40
35
30
25
5.5.3
Fight against hemp broomrape
(
Orobanche ramosa
)
20
15
10
5
Hemp broomrape (
Orobanche ramosa
) is a
parasitic weed that infests many crops, includ-
ing tomato, rape, tobacco, melon, potato and
hemp, as well as several weedy species includ-
ing black nightshade (
Solanum nigrum
),
fool's parsley (
Aethusa cynapium
), yarrow
(
Achillea millefolium
), pale persicaria
(
Persicaria lapathifolia
) and the chenopodi-
ums. It would appear that its propagation and
development are favoured by monocultures.
In l'Aube, the spread of this parasite has been
monitored closely by Le Chanvrière de l'Aube
since 2002. There are a number of ways of
fighting broomrape, based on its biology, but
they are of limited use.
0
1992 1993 1994 1995 1996 1997 1998 1999
Year
12-Sept
20-Sept
(c)
14
12
10
8
6
4
2
0
1992 1993 1994 1995 1996 1997 1998 1999
Year
12-Sept
20-Sept
Fig. 5.19.
Hurd yield (a), fibre content (b) and
seed yield (c) of the late variety, F74, harvested on
two different dates: 12 and 20 September (FNPC
results, 1992-1999).
Physical methods of control
•
Burying: at a depth of 50 cm the germina-
tive power of the
orobanche
seeds is
diminished and the roots of the host plant
will only reach these depths relatively late
in the season.
Heating: the seeds of
No herbicide is currently approved for use
on hemp. A few herbicides that could be used
are listed in Table 5.8; these have been tested
by the FDGEDA de l'Aube and by the FNPC.
Different trials have shown that hemp
crops are sensitive to herbicides, especially
when they are applied early. All the products
tested until now, with the exception of Lontrel,
induce plant losses if applied early. With this in
mind, it is clear that few products discriminate
in favour of hemp, that is to say, leave it
unharmed while dealing with weeds. That said,
•
orobanche
are killed
at high temperatures.
Manual removal and disposal.
•
•
Sow early to reduce infestation.
•
Crop rotation.
•
Fertilization: an increase in the dose of
nitrogen reduces the amount of infestation.
Use of false hosts on which
•
orobanche
can germinate but not establish itself.
Plant traps (to be destroyed once attacked
•
by the parasite).
