Black-Grass: The Definitive Resource

June and July are the best times to check black-grass populations and plan your control programme. 

Black-grass plants are visible above the crop canopy, so you can take the time to note black-grass hotspots and count the number of plants per square metre. This, combined with testing seed for herbicide resistance gives you an idea of the extent of the black-grass problem and how to tackle it.

Immediate steps include patch spraying, hand-rogueing and harvest weed seed management. Looking further ahead, there is the opportunity to plan crop rotation, cultivation and establishment for the coming season.

In-depth advice

• How to collect seed for black-grass resistance testing: An 8-step guide
• Guide to mapping black-grass

Cultural controls are a vital part of an integrated weed management programme and put less pressure on chemical applications. Cultivation can eliminate black-grass before the crop is planted, as well as create a good seedbed for crop establishment.

Cultivation is determined by soil type, crop choice, available machinery and your own preference. There is no single cultivation solution for black-grass control, but there are a number of principles that are worth paying attention to – for example:

• Burying black-grass seed through appropriate ploughing
• Encouraging germination through stale seedbeds
• Rolling after drilling

Choosing the right cultivation to suit the soil type on your farm (and the level of black-grass present) is a key part of control. Cultivations should be carefully considered; if not done correctly, they can accelerate the black-grass problem.

In-depth advice

• Five ways cultural controls can help eliminate black-grass
  
• Fine tuning cultivation equipment for improved black-grass control

Chemical controls can be broadly split into four groups: pre-emergence and post-emergence herbicides, non-selective control across whole fields (i.e. pre-drilling glyphosate), and patch spraying.

1. Pre-emergence

Pre-emergence herbicides such as Liberator (flufenacet + diflufenican) remain the backbone of chemical black-grass control and, when paired with a solid programme of cultural controls, can prevent black-grass from stealing yield.

Pre-ems are applied immediately after drilling and taken up by weeds either through roots absorbing the active ingredient from the layer containing the herbicide, or by shoots emerging through this treated layer. Application conditions can therefore greatly affect efficacy.

Flufenacet remains a highly effective active ingredient for pre-emergence black-grass control, and when used in Liberator in conjunction with Proclus (aclonifen)  typically achieves high levels of control. The addition of aclonifen can increase control by 10-15%.

Stacks or sequences of other actives, such as pendimethalin, prosulfocarb and tri-allate are also possible to improve control.

In-depth advice

• Four tips for getting the most out of pre-emergence herbicides in black-grass control
• Best techniques for applying pre-ems to fight black-grass
• Six ways to maximise pre-emergence herbicide efficacy

Post-emergence

Post-emergence herbicides are a vital part of integrated black-grass control programmes, especially where pre-em control has been compromised (e.g. due to weather) or weed emergence is protracted.

Contact post-emergence herbicides like Atlantis OD (mesosulfuron + iodosulfuron) and Monolith (mesosulfuron-methyl + propoxycarbazone) work by being absorbed through weed leaves. Hamlet (mesosulfuron, iodosulfuron + diflufenican) is also primarily contact-acting, but has some residual activity.

Ideally, growers should apply a post-emergence spray while black-grass is still small and easier to control.

In-depth advice

• Four tips for getting the most out of post-emergence herbicides in black-grass control

3. Non-selective (whole fields)

Non-selective herbicides, principally glyphosate, have been a cornerstone of black-grass control for many years.

Targeted use of glyphosate can significantly reduce the pressure on other in-crop chemistry, minimise the need for intensive cultivations and achieve big reductions in weed populations.

Spraying off weed flushes before autumn or spring drilling means less black-grass emerges within the crop, which would otherwise need controlling with pre- or post-emergence products.

However, over-reliance on glyphosate must be avoided and best practice followed to protect the efficacy of this important tool.

In-depth advice

• Effective use of glyphosate for black-grass control

4. Patch spraying

Where black-grass has emerged late or survived other chemical and cultural controls, the option of last resort where hand rogueing is not feasible may be to spray-off affected areas of crop with a non-selective herbicide, such as glyphosate.

Doing so before black-grass sets seed in late June into July is essential to prevent potentially high levels of seed return in following crops.

Mapping black-grass helps identify areas requiring patch spraying and best practice guidelines must be followed when using glyphosate in this way.

In-depth advice

• Effective use of glyphosate for black-grass control
• How to patch spray black-grass: Why, where and when