Integratedmanagement is the best solution to tackling the increasing threat fromblack-grass: the overwhelming conclusion from industry experts gathered at aBayer CropScience Black-Grass Task Force conference in Peterborough.
Takingdelegates from the theoretical to the practical, the experts shared theirknowledge and experience of how best to control this difficult grass-weed.
CraigKnight, a PhD student from the University of Warwick, is in year three of afour-year study exploring evolutionary dynamics of black-grass herbicideresistance. He explained his preliminary findings.
In2011, resistance to an ALS inhibitor affected 43% of populations tested, saidMr Knight. Resistance to an ACCaseinhibitor affected 100% of tested populations. In both cases enhanced metabolicresistance (EMR) is the primary mechanism. Retesting populations annually since2011 has shown that resistance levels havent changed much.
Unliketarget site resistance (TSR), which is specific to a particular mode of action,cultural control provides the best method of controlling EMR black-grass.
Thepoint was echoed by Andrew Cotton who drew on his 40 years of field experienceto demonstrate the effectiveness of stacked cultural control.
Aparticularly heavy population at a farm in Buckingham demanded a completeoverhaul of the rotation.
Needingsomething radical, we started with three spring crops – barley, oats andCanadian red wheat, back-to-back. All naturally competitive againstblack-grass, when preceded by multiple stale seedbeds we gradually gained theupper hand.
By2013 we were able to return to winter crops: oilseed rape in 2013 and wheatthis year.
Justbe careful with spring cropping to consider what chemistry is available, MrCotton warned, and of course, how its applied.
Thatwas a sentiment that formed the thrust of David Felces presentation.
Upto fifty per cent of a herbicides control is down to accurate timing andapplication technique.
Butwith sprayer operators under pressure to cover more acres within short weatherwindows increasing efficiency is a major challenge.
Itsimportant to choose where those efficiencies are made carefully as some actionsthat improve work rates can drastically reduce application efficacy.
If you dont hit the target you wont get thecontrol, says Mr Felce.
Takeforward speed. It has least impact on increasing output but the biggest effecton spray quality. Double the speed and turbulence increases four fold.
Equally,reducing water volumes, particularly at pre-emergence, can jeopardisecoverage.
Instead,growers should focus on logistics, he said. How can you make your fillingstations more efficient, for example?
Finally,Keith Norman – technical director at Velcourt – tried to give delegates aglimpse of the future, with a summary of the companys current research.
Companioncropping, catch cropping and bio-herbicides are all producing promising results,he noted.
Avenacinis a chemical produced by oats, which appears to have allelopathic qualities.When sown alongside a wheat crop, oats consistently reduce the number ofblack-grass heads. We suspect the avenacin is having a suppressive effect.
Oatsare also the subject of a joint study between Agrovista and Bayer CropScience,which sees black-oats sown in autumn to crowd-out early-germinatingblack-grass, and then a spring crop sown in the sprayed-off residue – with theadded advantage that reduced soil disturbance presents fewer opportunities forspring-germinating weeds.