Blackgrass control in wheat has got off to a bad start in many areas. The worst situations are first wheats following oilseed rape where blackgrass control in the rape crop was incomplete.
Subsequent management has been undermined by the weather - most notably the lack of rainfall to stimulate emergence in stale seedbeds followed by poor activity from residual herbicides applied to dry seedbeds.
Although moisture has since activated the residuals it has also encouraged a rapid flush of blackgrass which has grown away from the herbicides at 1 to 3 leaves - in some cases at very high populations.
Broad-leaved weeds have also survived most notably cranesbill. Atlantis/Horus applications have been pending for the last 2 or 3 weeks but with little opportunity for application as the weather has been so wet and windy.
Every week more fields are added to the list for autumn
Atlantis/Horus. At least conditions remain mild with soil temperatures
hovering around 9 - 10c maintaining active growth. This year we will
try the new Defy nozzles either the 03 or 035 to reduce drift whilst
maintaining a fine quality spray and also benefiting from the forward
facing angle of delivery.
Because they are Variable Pressure nozzles the spray quality is maintained across a range of working pressures allowing forward speed to be adjusted whilst maintaining output. Forward speeds will be limited to a maximum 12kmh. I have already heard of wheat crops that have been sprayed off with glyphosate because blackgrass has failed to succumb to a full autumn herbicide program!
I am less concerned about blackgrass control in oilseed rape at the
moment. Some very large canopies are shielding the grassweeds and the
soil but in many cases the grassweeds are still relatively small.
Walking rape crops over the last few days I have found plenty of
blackgrass at 1 - 2 leaf stage.
In those cases where blackgrass is tillered applications of propyzamide and/or carbetamide will be prioritised where the target is sufficiently visible. With soil temperatures only just approaching 8c and in present wet conditions risk of breakdown or movement of active ingredient to water is higher. Hopefully there will still be opportunities to spray over the next few weeks!
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