The
method of establishment will to a certain degree determine weed
control.
Where minimum tillage techniques have been used, grass weeds
will tend to be the main issue and where more soil has been
disturbed through conventional establishment methods broadleaf
weeds will be the major problem. The main yield robbers are
poppies, cleavers, chickweed, mayweed, sowthistles (harvest
problems) and grass weed species.
The armoury for weed control in oilseed rape has been greatly
reduced over the last year or two. Good general weed control
can only be achieved through applying pre-emergence weedkillers.
Weedkillers applied pre-emergence are based around metazachlor
and metazachlor + quinmerac. Clomozone
(Centium) can be added to this to give control of cleavers,
hedge mustard and improved chickweed control.
Both metazachlor and metazachlor + quinmerac can be used post-emergence,
however, rates need to be increased, cost goes up and weed control
reliability goes down. Thistles and mayweed can be controlled
by clopyralid (Shield), charlocks by cyanazine
(Fortrol) and cleavers, mayweed, thistle and groundsel
by clopyralid + picloram (Galera).
Grass
weed control.
Your approach to grass weed control will depend on whether resistance
has become a problem on your farm. This will further depend
on whether the problem is the Target Site type or Enhanced Metabolism
type of resistance. In both cases control will necessitate a
pre-emergence herbicide. Both metazachlor and trifluralin have
an affect on grass weeds, followed by an early post-emergence
treatment to ensure blackgrass and volunteers are treated when
relatively small.
For
most min-till/autocast type systems it will be necessary to
remove grass weeds and cereals at an early stage to avoid suppressive
competition. This treatment will give initial control of grass
weeds and some volunteers, however, in resistant situations,
control of grass weeds will be variable and there will be a
requirement for a robust follow up spray of propyzamide
or carbetamide to give a high degree of control.
Propyzamide/Carbetamide
Both these products are unaffected by blackgrass resistance,
but they can both suffer from variable control particularly
in a dry autumn. More reliable control can be obtained if seedbeds
are consolidated thereby improving moisture retention and encouraging
blackgrass roots to develop near the surface. If you are reliant
on these two chemicals we would always favour carbetamide rather
than propyzamide. Both offer a degree of broadleaf weed control.
Propyzamide will give control of chickweed and fat hen whilst
carbetamide will give control of speedwells (post-emergence),
cleaver, fat hen, small nettle, knotgrass and fumitory (pre-emergence).
There is now a dispersal formulation of carbetamide on the market
called Crawler.
One or two of the contact gramminicides available can be mixed
with either of these two products to enhance and upgrade their
reliability.
Falcon
+ Carbetamide.
Falcon + Kerb
Laser + Kerb
Please
consult your agronomist for the approved mixes.
AUTUMN
TREATMENTS
Pre-emergence - Option 1 (General broadleaf weeds + cleavers/hedge
mustard)
| Product |
Rate/Ha
|
Price/ha
|
| metazachlor |
0.75lt
|
£12.98
|
| trifluralin |
2.0
lt
|
£4.10
|
| clomozone
(Centium) |
0.25lt
|
£24.59
|
|
TOTAL
PRICE /HA
|
£41.67
|
The
above is suitable for general weed control with added cleaver,
chickweed and hedge mustard control. If poppies are deemed to
be a problem use a metazachlor + quinmerac mix.
Pre-emergence
- Option 2 (Cleavers/Poppies)
| Product |
Rate/Ha
|
Price/ha
|
| metazachlor
+ quinmerac |
2.0lt
|
£41.60
|
| trifluralin |
2.0
lt
|
£4.10
|
|
TOTAL
PRICE /HA
|
£45.70
|
Control
of early volunteers/blackgrass.
| Product |
Rate/Ha
|
Price/ha
|
| propaquizafop
(Falcon) |
0.5lt
|
£9.88
|
| Tepraloxydim
(Aramo) |
0.8
- 1.0lt
|
£12.60
- £15.75
|
|
Cycloxydim
(Laser) + Cropspray 11E
|
0.75lt
|
£16.85
|
Falcon
rate dependent on size of target and conditions at time
of application. Use mainly for volunteers. (0.25-0.5lt/ha).
It is reasonable on Brome but one of the weaker products on
tough/resistant blackgrass.
Aramo is good on volunteers, Brome and effective in both
target site and enhanced metabolism resistant situations although
like Laser we have seen problems. Apply no later than 9 leaves
or end of November.
Laser is good on volunteers, Brome and non-resistant
blackgrass although there can be problems in resistant situations.
Residual
Herbicides for control of grass weeds.
One of the following may be used
| Product |
Rate/Ha
|
Price/ha
|
| propyzamide
(400gm/lt liquid) |
1.75
- 2.10lts
|
£34.12
- £40.95
|
|
carbetamide (Carbetamex) |
3kgs
|
£32.70
|
| carbetamide
(Crawler) |
3.5kgs
|
£33.60
|
Apply
from 3-5-leaf stage. Propyzamide can be applied up to the end
of January and Carbetamide up to the end of February.
Spring
broad leaf weedkillers.
| Product |
Rate/Ha
|
Price/ha
|
| clopyralid
+ picloram (Galera) |
0.35lts
|
£19.92
|
|
cyanazine (Fortrol) |
1.0lt
|
£11.95
|
| clopyralid
(Dow Shield) |
0.35
- 0.5lts
|
£17.48
- £24.98
|
Galera
is suitable for mayweed and cleaver control.
Fortrol is suitable for charlock control (5 leaves and
frost hardy)
Dow Shield is suitable for mayweed, sowthistle and thistle
control.
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