Arable News

  • Written by: Farmers Guide
  • Posted:

Get on top of black-grass

Richard Peakeof Harlow Agricultural Merchants (HAM) says that growers need to get on top ofblack-grass before it gets on top of them. He has observed that this yearblack-grass appears to be a lot worse than in previous years. He calls itblack-grass on steroids!  “It isgrowing much more vigorously than normal. This may be because of the mildwinter followed by a year of low dormancy; so black-grass from July and August2013 all germinated coupled with seeds from 2011 and 2012. We have seencontinuous flushes of black-grass in September and October after eachcultivation and encouraged by the rainfall,” he says.


In HAM trials over aperiod of eight years, Richard Peake has been looking at ways to tackle thisinsidious weed problem.  I have foundover that time, the most successful herbicide programme appears to beglyphosate, applied within 1 to 2 days before drilling, followed by tri-allate(Avadex granules) and then full rate pendimethalin + flufenacet (Crystal) +full rate diflufenican (DFF).


Richard valuespendimethalin very highly and says that it is the best partner for flufenacet.Comparing Crystal with Liberator (flufenacet + DFF) over many years trials, hereports that Crystal consistently outperformed Liberator by 15%.  This is partly due to the residual activityof pendimethalin slowly grinding away at the weeds over the long cold winterperiod. In the same trials we have pegged down fixed quadrants to providemonthly counts of the emerged black-grass. These show that about 80% ofblack-grass initially gets through the Crystal + DFF but by March nearly 75% ofthese plants have died over the winter. I see pendimethalin as a vital componentin our armoury.


He noted that thetrials also confirm that timeliness of all herbicide inputs is crucial.  “Glyphosate timing must be spot on andmust be within one or two days before drilling. I know that this is easy to sayand not so easy to do.

But if you applyglyphosate one week before drilling, you may well be drilling into a bed oftiny black-grass and you will then be asking too much of the pre-emergencetreatments, because of such high weed populations.


Avadex timing isalso crucial, he says.  In my view itneeds to be applied within 2 days of drilling. Avadex works via vapour pressure. I believe it is taken up by thecoleoptile of the weed, so if black-grass is showing or is emerged, it is toolate for tri-allate and it will have little effect. If the soil is clinker dry,Avadex granules may struggle, along with other pre-emergence herbicides, but ifyou have the moisture there and you are truly pre-emergence, it will make avery important contribution, stopping up to 80% of black-grass emerging.


Because Avadex mustbe applied pre-emergence of the black-grass, it is essential that the gapbetween glyphosate and the Avadex is minimised. Richard suggests a maximum offour days.


I would advisegrowers to either get tooled up themselves to apply Avadex or make sure theyhave a strong relationship with their local contractor. You want to ensure thatthey appreciate just how important it is to get the Avadex granules on using acorrectly calibrated applicator at the right time. It is worth paying a bitmore for the spreading to be timed correctly, not several days later when thecontractor can fit it in, he says.


Having timelyapplied glyphosate and Avadex granules, the following spray of Crystal + DFFcan then be applied either pre or early post-emergence preferably tramlinesvisible at the latest.

In HAM trials overthe last three years with correct timings the Avadex followed by Crystal +DFFprogramme has achieved 99% control of strains of black-grass that are highlyresistant to Atlantis.


This treatmentcombination also gives excellent control of a very wide range of weedsincluding wild-oats, rye-grass, sterile brome (but not meadow-brome) and mostbroad-leaved weeds including cleavers – so much so that you can easily make a costsaving on a spring-applied broad-leaved weed herbicide. These more robustautumn programmes that we are talking about cost over 100/hectare now, hesays.


Richard Peake saysthat chemistry alone is not the total solution however.  Farmers are realising that they cant justrely on chemical solutions to control black-grass any more. They need to adoptnon-chemical methods too. Growers need to plough more and use higher seed ratesin difficult establishment conditions to provide more competition. Moving tocompetitive spring crops is also a positive rotational option. I would classifycompetitive spring crops as spring barley and well-grown spring rape.

Avoidnon-competitive spring ones such as peas and beans where chemistry is limited.Another consideration could be winter barley which is four times as competitiveas winter wheat and provides a good entry to rape. This crop can be usedstrategically in the fight against black-grass and help satisfy the new threecrop rule.


  • Written by: Farmers Guide
  • Posted:
Prev Story:CAP decision is sensible compromise for farming and environmentNext Story:New stewardship initiative on the use of metazachlor to protect water