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 autumnAtlantis/Horus. At least conditions remain mild with soil temperatureshovering around 9 – 10c maintaining active growth. This year we willtry the new Defy nozzles either the 03 or 035 to reduce drift whilstmaintaining a fine quality spray and also benefiting from the forwardfacing angle of delivery.
Because they are Variable Pressure nozzles the spray quality ismaintained across a range of working pressures allowing forward speedto be adjusted whilst maintaining output. Forward speeds will belimited to a maximum 12kmh. I have already heard of wheat crops thathave been sprayed off with glyphosate because blackgrass has failed tosuccumb to a full autumn herbicide program!
I am less concerned about blackgrass control in oilseed rape at themoment. Some very large canopies are shielding the grassweeds and thesoil but in many cases the grassweeds are still relatively small. Walking rape crops over the last few days I have found plenty ofblackgrass at 1 – 2 leaf stage.
In those cases where blackgrass is tillered applications ofpropyzamide and/or carbetamide will be prioritised where the target issufficiently visible. With soil temperatures only just approaching 8cand in present wet conditions risk of breakdown or movement of activeingredient to water is higher. Hopefully there will still beopportunities to spray over the next few weeks!