With last autumn’s wet weather significantly impacting winter cereal crop establishment, many growers will be contemplating bringing this year’s drilling dates forward into early October.

However, Adama’s Bill Lankford is arguing that this strategy goes against all best practice advice for controlling black-grass populations and explains why – alongside weed mapping, rotation planning, cultivation technique and herbicide programmes – delaying drilling is still one of the key tactics for beating black-grass.

With fewer herbicides to choose from and resistance to some active ingredients on the rise, black-grass remains a significant problem in large parts of the UK – increasingly in Scotland – with the extent of the problem largely dependent on cultivation strategy, rotation, soil type, drainage and herbicide inputs.

Mr Lankford said: “In the worst affected areas, it is commonly accepted that infestations will never be totally eradicated, but as long as adequate measures are put in place, black-grass populations can be managed down to an acceptable level.

“In addition to the use of a robust programme of herbicide applications – including pre-emergence and early post-emergence residual treatments – the key advice is to introduce more spring crops into the rotation and to delay the drilling of winter crops until mid-October or beyond.

“Also, paying attention to details such as drilling badly infected fields last, reducing sprayer forward operating speeds and using appropriate spray nozzles to maximise coverage and reduce drift can all contribute to improved black-grass control,” he said.

When selecting a herbicide, consideration should be given to the ability of those compounds to remain effective in variable seedbed conditions.

Mr Lankford said the following factors should therefore be assessed ahead of and during the spraying season, with each treatment customised and adapted using a combination of active ingredients to suit the prevailing field conditions:

n Water solubility: Actives with good water solubility ratings (such as chlorotoluron and flufenacet) will be taken up more easily in early, drier seedbeds (eg at pre-emergence and early post-emergence timings).

n Half-life duration: Those with an extended half-life duration (the time it takes for the active ingredient’s parent compound to degrade by 50%) will provide reliable residual activity for longer after application.

“The message is clear – with variable and unpredictable weather patterns adding to the crop protection challenge, growers shouldn’t simply rely on those active ingredients they’ve used in the past.

“Instead, professional agronomic guidance should be taken to ensure the spray programme is viable for the current cropping conditions and, where necessary, tailored by selecting those active ingredients which will provide the best level and longevity of protection in the prevailing climatic and soil conditions.

“For example, Tower (chlorotoluron 250 g/l, pendimethalin 300 g/l and diflufenican 40 g/l) will ensure good uptake even in the driest conditions thanks to its CTU component and will also provide good longevity of efficacy thanks to its PDM and DFF components. Likewise, Herold (flufenacet 400g/l and diflufenican 200 g/l) will also provide good efficacy in dry conditions and also offers extended longevity.

“Alternatively, Anthem (pendimethalin 400 g/l) will provide good all-round protection and longevity in a wide range of conditions,” he said.

As well as enabling the first flush of black-grass seedlings to be destroyed, delaying drilling can also improve the efficacy of pre-emergence herbicides which will be more effective when applied in damp soil conditions. Black-grass plants which emerge in later drilled crops also tend to be less competitive and may produce fewer seeds per plant.

Timing of drilling, therefore remains key in the fight against black-grass and so waiting until as late as possible – from mid-October and into November for the best results – is the main advice. This could make drilling conditions trickier, leading to the recent rise in popularity of lighter/smaller seed drills which can still be used in wetter conditions, he argued.

Black-grass control

in a nutshell:

n Delay autumn drilling until after the first flush of black-grass plants has been sprayed off with glyphosate;

n Use non-chemical methods in combination with herbicides to improve control;

n Use a mix of active ingredients with different modes of action;

n Apply a robust pre-emergence stack within 48 hours of drilling;

n Ensure good application coverage by using forward and rear-facing nozzles to apply pre-emergence treatments to a fine, firm seedbed;

n Keep water volume and spray at a sensible speed (12km/h) to ensure complete coverage;

n Return with a post-emergence treatment when subsequent black-grass plants are at the one/two leaf stage;

n Tailor treatments to each individual field according to soil type, rotation, previous cultivation technique, prevailing climatic conditions and current black-grass populations.